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Certain directional anatomical terms appear throughout this and any other anatomy textbook ([Figure 1.13](#page-33-0)). These terms are essential for describing the relative locations of different body structures. For instance, an anatomist might describe one band of tissue as "inferior to" another or a physician m...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Directional Terms", "token_count": 499, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A section is a two-dimensional surface of a three-dimensional structure that has been cut. Modern medical imaging devices enable clinicians to obtain "virtual sections" of living bodies. We call these scans. Body sections and scans can be correctly interpreted, however, only if the viewer understands the plane alon...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Body Planes", "token_count": 341, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The body maintains its internal organization by means of membranes, sheaths, and other structures that separate compartments. The dorsal (posterior) cavity and the ventral (anterior) cavity are the largest body compartments ([Figure](#page-35-0) [1.15](#page-35-0)). These cavities contain and protect delica...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Body Cavities and Serous Membranes", "token_count": 203, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The posterior (dorsal) and anterior (ventral) cavities are each subdivided into smaller cavities. In the posterior (dorsal) cavity, the cranial cavity houses the brain, and the spinal cavity (or vertebral cavity) encloses the spinal cord. Just as the brain and spinal cord make up a continuous, uninterrupted str...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Subdivisions of the Posterior (Dorsal) and Anterior (Ventral) Cavities", "token_count": 334, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
To promote clear communication, for instance about the location of a patient's abdominal pain or a suspicious mass, health care providers typically divide up the cavity into either nine regions or four quadrants ([Figure 1.16](#page-36-0)). ![](_page_36_Figure_1.jpeg) **Figure 1.16 Regions and Quadrants of the ...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Abdominal Regions and Quadrants", "token_count": 205, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A serous membrane (also referred to a serosa) is one of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities. The parietal layers of the membranes line the walls of the body cavity (pariet- refers to a cavity wall). The visceral layer of the membrane covers the organs (the ...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Membranes of the Anterior (Ventral) Body Cavity", "token_count": 437, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Discuss the uses and drawbacks of X-ray imaging - Identify four modern medical imaging techniques and how they are used For thousands of years, fear of the dead and legal sanctions limited the ability of anatomists and physicians to study the internal structures of...	{ "Header 1": "1.7 \| Medical Imaging", "token_count": 260, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
German physicist Wilhelm Röntgen (1845–1923) was experimenting with electrical current when he discovered that a mysterious and invisible "ray" would pass through his flesh but leave an outline of his bones on a screen coated with a metal compound. In 1895, Röntgen made the first durable record of the internal parts of...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "X-Rays", "token_count": 493, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Tomography refers to imaging by sections. Computed tomography (CT) is a noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body ([Figure](#page-38-0) [1.19a](#page-38-0)). The technique was invented in the 1970s a...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "Computed Tomography", "token_count": 583, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant ...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "Magnetic Resonance Imaging", "token_count": 501, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Positron emission tomography (PET) is a medical imaging technique involving the use of so-called radiopharmaceuticals, substances that emit radiation that is short-lived and therefore relatively safe to administer to the body. Although the first PET scanner was introduced in 1961, it took 15 more years before radio...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "Positron Emission Tomography", "token_count": 274, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
abdominopelvic cavity division of the anterior (ventral) cavity that houses the abdominal and pelvic viscera anabolism assembly of more complex molecules from simpler molecules anatomical position standard reference position used for describing locations and directions on the human body anatomy sc...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "KEY TERMS", "token_count": 1572, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Ancient Greek and Latin words are used to build anatomical terms. A standard reference position for mapping the body's structures is the normal anatomical position. Regions of the body are identified using terms such as "occipital" that are more precise than common words and phrases such as "the back of the head." Dire...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "[1.6 Anatomical Terminology](#page-31-0)", "token_count": 213, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - Describe the fundamental composition of matter - Identify the three subatomic particles - Identify the four most abundant elements in the body - Explain the relationship between an atom's number of electrons and its relative stability - Distinguish between ionic bon...	{ "Header 1": "Chapter Objectives", "token_count": 398, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Discuss the relationships between matter, mass, elements, compounds, atoms, and subatomic particles - Distinguish between atomic number and mass number - Identify the key distinction between isotopes of the same element - Explain how electrons occupy electron shells ...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "token_count": 270, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Atoms are made up of even smaller subatomic particles, three types of which are important: the proton, neutron, and electron. The number of positively-charged protons and non-charged ("neutral") neutrons, gives mass to the atom, and the number of each in the nucleus of the atom determine the element. The nu...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Atomic Structure and Energy", "token_count": 449, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
An atom of carbon is unique to carbon, but a proton of carbon is not. One proton is the same as another, whether it is found in an atom of carbon, sodium (Na), or iron (Fe). The same is true for neutrons and electrons. So, what gives an element its distinctive properties—what makes carbon so different from sodium or ir...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Atomic Number and Mass Number", "token_count": 725, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Although each element has a unique number of protons, it can exist as different isotopes. An isotope is one of the different forms of an element, distinguished from one another by different numbers of neutrons. The standard isotope of carbon is <sup>12</sup>C, commonly called carbon twelve. <sup>12</sup>C has six p...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Isotopes", "token_count": 496, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The controlled use of radioisotopes has advanced medical diagnosis and treatment of disease. Interventional radiologists are physicians who treat disease by using minimally invasive techniques involving radiation. Many conditions that could once only be treated with a lengthy and traumatic operation can now be treated ...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Interventional Radiologist", "token_count": 481, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the human body, atoms do not exist as independent entities. Rather, they are constantly reacting with other atoms to form and to break down more complex substances. To fully understand anatomy and physiology you must grasp how atoms participate in such reactions. The key is understanding the behavior of electrons. ...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "The Behavior of Electrons", "token_count": 970, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain the relationship between molecules and compounds - Distinguish between ions, cations, and anions - Identify the key difference between ionic and covalent bonds - Distinguish between nonpolar and polar covalent bonds - Explain how water molecules link via hydr...	{ "Header 1": "2.2 \| Chemical Bonds", "token_count": 398, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Recall that an atom typically has the same number of positively charged protons and negatively charged electrons. As long as this situation remains, the atom is electrically neutral. But when an atom participates in a chemical reaction that results in the donation or acceptance of one or more electrons, the atom will t...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Ions and Ionic Bonds", "token_count": 237, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Potassium (K), for instance, is an important element in all body cells. Its atomic number is 19. It has just one electron in its valence shell. This characteristic makes potassium highly likely to participate in chemical reactions in which it donates one electron. (It is easier for potassium to donate one electron than...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "50 CHAPTER 2 \| THE CHEMICAL LEVEL OF ORGANIZATION", "token_count": 714, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Groups of legislators with completely opposite views on a particular issue are often described as "polarized" by news writers. In chemistry, a polar molecule is a molecule that contains regions that have opposite electrical charges. Polar molecules occur when atoms share electrons unequally, in polar covalent bonds...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Polar Covalent Bonds", "token_count": 230, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
What is true for the bonds is true for the water molecule as a whole; that is, the oxygen region has a slightly negative charge and the regions of the hydrogen atoms have a slightly positive charge. These charges are often referred to as "partial charges" because the strength of the charge is less than one full electro...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Figure 2.10 Polar Covalent Bonds in a Water Molecule", "token_count": 263, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another molecule. In other words, hydrogen bonds always include hydrogen that is already part of a polar molecul...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Hydrogen Bonds", "token_count": 416, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Chemical reactions require a sufficient amount of energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine you are building a brick wall. The energy...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "The Role of Energy in Chemical Reactions", "token_count": 418, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
You have already learned that chemical energy is absorbed, stored, and released by chemical bonds. In addition to chemical energy, mechanical, radiant, and electrical energy are important in human functioning. - Mechanical energy, which is stored in physical systems such as machines, engines, or the human body, direc...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Forms of Energy Important in Human Functioning", "token_count": 230, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
All chemical reactions begin with a reactant, the general term for the one or more substances that enter into the reaction. Sodium and chloride ions, for example, are the reactants in the production of table salt. The one or more substances produced by a chemical reaction are called the product. In chemical r...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Characteristics of Chemical Reactions", "token_count": 809, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
If chemical reactions are to occur quickly, the atoms in the reactants have to have easy access to one another. Thus, the greater the surface area of the reactants, the more readily they will interact. When you pop a cube of cheese into your mouth, you chew it before you swallow it. Among other things, chewing increase...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Properties of the Reactants", "token_count": 204, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
For two chemicals in nature to react with each other they first have to come into contact, and this occurs through random collisions. Because heat helps increase the kinetic energy of atoms, ions, and molecules, it promotes their collision. But in the body, extremely high heat—such as a very high fever—can damage body ...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Enzymes and Other Catalysts", "token_count": 438, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Compare and contrast inorganic and organic compounds - Identify the properties of water that make it essential to life - Explain the role of salts in body functioning - Distinguish between acids and bases, and explain their role in pH - Discuss the role of buffers in...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "token_count": 353, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A mixture is a combination of two or more substances, each of which maintains its own chemical identity. In other words, the constituent substances are not chemically bonded into a new, larger chemical compound. The concept is easy to imagine if you think of powdery substances such as flour and sugar; when you stir the...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Water as a Component of Liquid Mixtures", "token_count": 452, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Various mixtures of solutes and water are described in chemistry. The concentration of a given solute is the number of particles of that solute in a given space (oxygen makes up about 21 percent of atmospheric air). In the bloodstream of humans, glucose concentration is usually measured in milligram (mg) per deciliter ...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Concentrations of Solutes", "token_count": 583, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Two types of chemical reactions involve the creation or the consumption of water: dehydration synthesis and hydrolysis. - In dehydration synthesis, one reactant gives up an atom of hydrogen and another reactant gives up a hydroxyl group (OH) in the synthesis of a new product. In the formation of their covalent bond, ...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "The Role of Water in Chemical Reactions", "token_count": 340, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Recall that salts are formed when ions form ionic bonds. In these reactions, one atom gives up one or more electrons, and thus becomes positively charged, whereas the other accepts one or more electrons and becomes negatively charged. You can now define a salt as a substance that, when dissolved in water, dissociates...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Salts", "token_count": 329, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
An acid is a substance that releases hydrogen ions (H<sup>+</sup> ) in solution ([Figure 2.16](#page-68-0)a). Because an atom of hydrogen has just one proton and one electron, a positively charged hydrogen ion is simply a proton. This solitary proton is highly likely to participate in chemical reactions. Strong...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Acids", "token_count": 332, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A base is a substance that releases hydroxyl ions (OH– ) in solution, or one that accepts H<sup>+</sup> already present in solution (see [Figure 2.16](#page-68-0)b). The hydroxyl ions or other base combine with H<sup>+</sup> present to form a water molecule, thereby removing H<sup>+</sup> and reducing the solut...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Bases", "token_count": 212, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The relative acidity or alkalinity of a solution can be indicated by its pH. A solution's pH is the negative, base-10 logarithm of the hydrogen ion (H<sup>+</sup> ) concentration of the solution. As an example, a pH 4 solution has an H<sup>+</sup> concentration that is ten times greater than that of a pH 5 solution...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "The Concept of pH", "token_count": 401, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pH of human blood normally ranges from 7.35 to 7.45, although it is typically identified as pH 7.4. At this slightly basic pH, blood can reduce the acidity resulting from the carbon dioxide (CO2) constantly being released into the bloodstream by the trillions of cells in the body. Homeostatic mechanisms (along with...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Buffers", "token_count": 280, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Excessive acidity of the blood and other body fluids is known as acidosis. Common causes of acidosis are situations and disorders that reduce the effectiveness of breathing, especially the person's ability to exhale fully, which causes a buildup of CO<sup>2</sup> (and H<sup>+</sup> ) in the bloodstream. Acidosis can al...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Acids and Bases", "token_count": 350, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Identify four types of organic molecules essential to human functioning - Explain the chemistry behind carbon's affinity for covalently bonding in organic compounds - Provide examples of three types of carbohydrates, and identify the primary functions of carbohydrate...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "token_count": 207, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
What makes organic compounds ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four electrons in their valence shell, and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence ...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "The Chemistry of Carbon", "token_count": 557, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Carbon's affinity for covalent bonding means that many distinct and relatively stable organic molecules nevertheless readily form larger, more complex molecules. Any large molecule is referred to as macromolecule (macro- = "large"), and the organic compounds in this section all fit this description. However, some m...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Table 2.1", "token_count": 260, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A disaccharide is a pair of monosaccharides. Disaccharides are formed via dehydration synthesis, and the bond linking them is referred to as a glycosidic bond (glyco- = "sugar"). Three disaccharides (shown in [Figure 2.19](#page-73-0)) are important to humans. These are sucrose, commonly referred to as table su...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Disaccharides", "token_count": 312, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Polysaccharides can contain a few to a thousand or more monosaccharides. Three are important to the body ([Figure 2.20](#page-74-0)): - Starches are polymers of glucose. They occur in long chains called amylose or branched chains called amylopectin, both of which are stored in plant-based foods and are relatively...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Polysaccharides", "token_count": 281, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The body obtains carbohydrates from plant-based foods. Grains, fruits, and legumes and other vegetables provide most of the carbohydrate in the human diet, although lactose is found in dairy products. Although most body cells can break down other organic compounds for fuel, all body cells can use glucose. Moreover, n...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Functions of Carbohydrates", "token_count": 342, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A triglyceride is one of the most common dietary lipid groups, and the type found most abundantly in body tissues. This compound, which is commonly referred to as a fat, is formed from the synthesis of two types of molecules ([Figure 2.21](#page-75-0)): - A glycerol backbone at the core of triglycerides, cons...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Triglycerides", "token_count": 795, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As its name suggests, a phospholipid is a bond between the glycerol component of a lipid and a phosphorous molecule. In fact, phospholipids are similar in structure to triglycerides. However, instead of having three fatty acids, a phospholipid is generated from a diglyceride, a glycerol with just two fatty acid cha...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Phospholipids", "token_count": 369, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A steroid compound (referred to as a sterol) has as its foundation a set of four hydrocarbon rings bonded to a variety of other atoms and molecules (see [Figure 2.23b](#page-77-0)). Although both plants and animals synthesize sterols, the type that makes the most important contribution to human structure and fu...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Steroids", "token_count": 230, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Proteins are polymers made up of nitrogen-containing monomers called amino acids. An amino acid is a molecule composed of an amino group and a carboxyl group, together with a variable side chain. Just 20 different amino acids contribute to nearly all of the thousands of different proteins important in human structu...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Microstructure of Proteins", "token_count": 220, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Notice that all amino acids contain both an acid (the carboxyl group) and a base (the amino group) (amine = "nitrogencontaining"). For this reason, they make excellent buffers, helping the body regulate acid–base balance. What distinguishes the 20 amino acids from one another is their variable group, which is referred ...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Figure 2.24 Structure of an Amino Acid", "token_count": 428, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Just as a fork cannot be used to eat soup and a spoon cannot be used to spear meat, a protein's shape is essential to its function. A protein's shape is determined, most fundamentally, by the sequence of amino acids of which it is made ([Figure](#page-80-0) [2.26a](#page-80-0)). The sequence is called the primary s...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Shape of Proteins", "token_count": 913, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
If you were trying to type a paper, and every time you hit a key on your laptop there was a delay of six or seven minutes before you got a response, you would probably get a new laptop. In a similar way, without enzymes to catalyze chemical reactions, the human body would be nonfunctional. It functions only because enz...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Proteins Function as Enzymes", "token_count": 389, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Advertisements for protein bars, powders, and shakes all say that protein is important in building, repairing, and maintaining muscle tissue, but the truth is that proteins contribute to all body tissues, from the skin to the brain cells. Also, certain proteins act as hormones, chemical messengers that help regulate bo...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Other Functions of Proteins", "token_count": 270, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The fourth type of organic compound important to human structure and function are the nucleotides ([Figure 2.28](#page-82-0)). A nucleotide is one of a class of organic compounds composed of three subunits: - one or more phosphate groups - a pentose sugar: either deoxyribose or ribose - a nitrogen-containing ...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Nucleotides", "token_count": 211, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The nucleic acids differ in their type of pentose sugar. Deoxyribonucleic acid (DNA) is nucleotide that stores genetic information. DNA contains deoxyribose (so-called because it has one less atom of oxygen than ribose) plus one phosphate group and one nitrogen-containing base. The "choices" of base for DNA are ade...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Nucleic Acids", "token_count": 523, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When a phosphate group is cleaved from ATP, the products are adenosine diphosphate (ADP) and inorganic phosphate (Pi). This hydrolysis reaction can be written: $$ATP + H_2O \rightarrow ADP + P_i + energy$$ Removal of a second phosphate leaves adenosine monophosphate (AMP) and two phosphate groups. Again, these reac...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Figure 2.30 Structure of Adenosine Triphosphate (ATP)", "token_count": 242, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
- acid compound that releases hydrogen ions (H<sup>+</sup> ) in solution - activation energy amount of energy greater than the energy contained in the reactants, which must be overcome for a reaction to proceed - adenosine triphosphate (ATP) nucleotide containing ribose and an adenine base that is essential...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "KEY TERMS", "token_count": 1494, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The human body is composed of elements, the most abundant of which are oxygen (O), carbon (C), hydrogen (H) and nitrogen (N). You obtain these elements from the foods you eat and the air you breathe. The smallest unit of an element that retains all of the properties of that element is an atom. But, atoms themselves con...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.1 Elements a](#page-48-1)[nd Atoms: The Building Blocks of Matter](#page-49-0)", "token_count": 294, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Each moment of life, atoms of oxygen, carbon, hydrogen, and the other elements of the human body are making and breaking chemical bonds. Ions are charged atoms that form when an atom donates or accepts one or more negatively charged electrons. Cations (ions with a positive charge) are attracted to anions (ions with a n...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.2 Chemical Bonds](#page-56-0)", "token_count": 221, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Chemical reactions, in which chemical bonds are broken and formed, require an initial investment of energy. Kinetic energy, the energy of matter in motion, fuels the collisions of atoms, ions, and molecules that are necessary if their old bonds are to break and new ones to form. All molecules store potential energy, wh...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.3 Chemical Reactions](#page-61-0)", "token_count": 237, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Inorganic compounds essential to human functioning include water, salts, acids, and bases. These compounds are inorganic; that is, they do not contain both hydrogen and carbon. Water is a lubricant and cushion, a heat sink, a component of liquid mixtures, a byproduct of dehydration synthesis reactions, and a reactant i...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.4 Inorganic Compounds Essential to Human Functioning](#page-64-0)", "token_count": 298, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Organic compounds essential to human functioning include carbohydrates, lipids, proteins, and nucleotides. These compounds are said to be organic because they contain both carbon and hydrogen. Carbon atoms in organic compounds readily share electrons with hydrogen and other atoms, usually oxygen, and sometimes nitrogen...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.5 Organic Compounds Essential to Human Functioning](#page-70-0)", "token_count": 443, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - Describe the structure and function of the cell membrane, including its regulation of materials into and out of the cell - Describe the functions of the various cytoplasmic organelles - Explain the structure and contents of the nucleus, as well as the process of DNA...	{ "Header 1": "Chapter Objectives", "token_count": 743, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The cell membrane is an extremely pliable structure composed primarily of back-to-back phospholipids (a "bilayer"). Cholesterol is also present, which contributes to the fluidity of the membrane, and there are various proteins embedded within the membrane that have a variety of functions. A single phospholipid mo...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Structure and Composition of the Cell Membrane", "token_count": 712, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The lipid bilayer forms the basis of the cell membrane, but it is peppered throughout with various proteins. Two different types of proteins that are commonly associated with the cell membrane are the integral proteins and peripheral protein ([Figure 3.4](#page-95-0)). As its name suggests, an integral protein ...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Membrane Proteins", "token_count": 623, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
One of the great wonders of the cell membrane is its ability to regulate the concentration of substances inside the cell. These substances include ions such as Ca++, Na<sup>+</sup> , K<sup>+</sup> , and Cl– ; nutrients including sugars, fatty acids, and amino acids; and waste products, particularly carbon dioxide (CO2)...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Transport across the Cell Membrane", "token_count": 324, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In order to understand how substances move passively across a cell membrane, it is necessary to understand concentration gradients and diffusion. A concentration gradient is the difference in concentration of a substance across a space. Molecules (or ions) will spread/diffuse from where they are more concentrated...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Passive Transport", "token_count": 1829, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
For all of the transport methods described above, the cell expends no energy. Membrane proteins that aid in the passive transport of substances do so without the use of ATP. During active transport, ATP is required to move a substance across a membrane, often with the help of protein carriers, and usually against its...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Active Transport", "token_count": 1945, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Cystic fibrosis (CF) affects approximately 30,000 people in the United States, with about 1,000 new cases reported each year. The genetic disease is most well known for its damage to the lungs, causing breathing difficulties and chronic lung infections, but it also affects the liver, pancreas, and intestines. Only abou...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Cell: Cystic Fibrosis", "token_count": 693, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the structure and function of the cellular organelles associated with the endomembrane system, including the endoplasmic reticulum, Golgi apparatus, and lysosomes - Describe the structure and function of mitochondria and peroxisomes - Explain the three compo...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "token_count": 380, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The endoplasmic reticulum (ER) is a system of channels that is continuous with the nuclear membrane (or "envelope") covering the nucleus and composed of the same lipid bilayer material. The ER can be thought of as a series of winding thoroughfares similar to the waterway canals in Venice. The ER provides passages t...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Endoplasmic Reticulum", "token_count": 710, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The Golgi apparatus is responsible for sorting, modifying, and shipping off the products that come from the rough ER, much like a post-office. The Golgi apparatus looks like stacked flattened discs, almost like stacks of oddly shaped pancakes. Like the ER, these discs are membranous. The Golgi apparatus has two dis...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "The Golgi Apparatus", "token_count": 310, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Some of the protein products packaged by the Golgi include digestive enzymes that are meant to remain inside the cell for use in breaking down certain materials. The enzyme-containing vesicles released by the Golgi may form new lysosomes, or fuse with existing, lysosomes. A lysosome is an organelle that contains en...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Lysosomes", "token_count": 373, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A mitochondrion (plural = mitochondria) is a membranous, bean-shaped organelle that is the "energy transformer" of the cell. Mitochondria consist of an outer lipid bilayer membrane as well as an additional inner lipid bilayer membrane ([Figure 3.16](#page-106-0)). The inner membrane is highly folded into windin...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Mitochondria", "token_count": 410, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Like lysosomes, a peroxisome is a membrane-bound cellular organelle that contains mostly enzymes (Figure 3.17). Peroxisomes perform a couple of different functions, including lipid metabolism and chemical detoxification. In contrast to the digestive enzymes found in lysosomes, the enzymes within peroxisomes serve t...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Peroxisomes", "token_count": 770, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The free radical theory on aging was originally proposed in the 1950s, and still remains under debate. Generally speaking, the free radical theory of aging suggests that accumulated cellular damage from oxidative stress contributes to the physiological and anatomical effects of aging. There are two significantly differ...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Cell: The Free Radical Theory", "token_count": 254, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Much like the bony skeleton structurally supports the human body, the cytoskeleton helps the cells to maintain their structural integrity. The cytoskeleton is a group of fibrous proteins that provide structural support for cells, but this is only one of the functions of the cytoskeleton. Cytoskeletal components are...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "The Cytoskeleton", "token_count": 1000, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the structure and features of the nuclear membrane - List the contents of the nucleus - Explain the organization of the DNA molecule within the nucleus - Describe the process of DNA replication The nucleus is the largest and most prominent of a cell's orga...	{ "Header 1": "3.3 \| The Nucleus and DNA Replication", "token_count": 958, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Like most other cellular organelles, the nucleus is surrounded by a membrane called the nuclear envelope. This membranous covering consists of two adjacent lipid bilayers with a thin fluid space in between them. Spanning these two bilayers are nuclear pores. A nuclear pore is a tiny passageway for the passage o...	{ "Header 1": "3.3 \| The Nucleus and DNA Replication", "Header 3": "Organization of the Nucleus and Its DNA", "token_count": 472, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In order for an organism to grow, develop, and maintain its health, cells must reproduce themselves by dividing to produce two new daughter cells, each with the full complement of DNA as found in the original cell. Billions of new cells are produced in an adult human every day. Only very few cell types in the body do n...	{ "Header 1": "3.3 \| The Nucleus and DNA Replication", "Header 3": "DNA Replication", "token_count": 1088, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain how the genetic code stored within DNA determines the protein that will form - Describe the process of transcription - Describe the process of translation - Discuss the function of ribosomes It was mentioned earlier that DNA provides a "blueprint" for the c...	{ "Header 1": "3.4 \| Protein Synthesis", "token_count": 613, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
DNA is housed within the nucleus, and protein synthesis takes place in the cytoplasm, thus there must be some sort of intermediate messenger that leaves the nucleus and manages protein synthesis. This intermediate messenger is messenger RNA (mRNA), a single-stranded nucleic acid that carries a copy of the genetic c...	{ "Header 1": "3.4 \| Protein Synthesis", "Header 3": "From DNA to RNA: Transcription", "token_count": 958, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Like translating a book from one language into another, the codons on a strand of mRNA must be translated into the amino acid alphabet of proteins. Translation is the process of synthesizing a chain of amino acids called a polypeptide. Translation requires two major aids: first, a "translator," the molecule tha...	{ "Header 1": "3.4 \| Protein Synthesis", "Header 3": "From RNA to Protein: Translation", "token_count": 1124, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the stages of the cell cycle - Discuss how the cell cycle is regulated - Describe the implications of losing control over the cell cycle - Describe the stages of mitosis and cytokinesis, in order So far in this chapter, you have read numerous times of the ...	{ "Header 1": "3.5 \| Cell Growth and Division", "token_count": 354, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A cell grows and carries out all normal metabolic functions and processes in a period called G1 ([Figure 3.30](#page-120-0)). G1 phase (gap 1 phase) is the first gap, or growth phase in the cell cycle. For cells that will divide again, G1 is followed by replication of the DNA, during the S phase. The *S phase...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Interphase", "token_count": 340, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Billions of cells in the human body divide every day. During the synthesis phase (S, for DNA synthesis) of interphase, the amount of DNA within the cell precisely doubles. Therefore, after DNA replication but before cell division, each cell actually contains two copies of each chromosome. Each copy of the chromosome ...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "The Structure of Chromosomes", "token_count": 301, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The mitotic phase of the cell typically takes between 1 and 2 hours. During this phase, a cell undergoes two major processes. First, it completes mitosis, during which the contents of the nucleus are equitably pulled apart and distributed between its two halves. Cytokinesis then occurs, dividing the cytoplasm and c...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Mitosis and Cytokinesis", "token_count": 1624, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As the cell proceeds through its cycle, each phase involves certain processes that must be completed before the cell should advance to the next phase. A checkpoint is a point in the cell cycle at which the cycle can be signaled to move forward or stopped. At each of these checkpoints, different varieties of molecul...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Mechanisms of Cell Cycle Control", "token_count": 348, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Most people understand that cancer or tumors are caused by abnormal cells that multiply continuously. If the abnormal cells continue to divide unstopped, they can damage the tissues around them, spread to other parts of the body, and eventually result in death. In healthy cells, the tight regulation mechanisms of the c...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "The Cell Cycle Out of Control: Implications", "token_count": 243, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Cancer is an extremely complex condition, capable of arising from a wide variety of genetic and environmental causes. Typically, mutations or aberrations in a cell's DNA that compromise normal cell cycle control systems lead to cancerous tumors. Cell cycle control is an example of a homeostatic mechanism that maintains...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Cancer Arises from Homeostatic Imbalances", "token_count": 724, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A stem cell is an unspecialized cell that can divide without limit as needed and can, under specific conditions, differentiate into specialized cells. Stem cells are divided into several categories according to their potential to differentiate. The first embryonic cells that arise from the division of the zygote ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "Stem Cells", "token_count": 556, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When a cell differentiates (becomes more specialized), it may undertake major changes in its size, shape, metabolic activity, and overall function. Because all cells in the body, beginning with the fertilized egg, contain the same DNA, how do the different cell types come to be so different? The answer is analogous to ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "Differentiation", "token_count": 283, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Stem cell research aims to find ways to use stem cells to regenerate and repair cellular damage. Over time, most adult cells undergo the wear and tear of aging and lose their ability to divide and repair themselves. Stem cells do not display a particular morphology or function. Adult stem cells, which exist as a small ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "Stem Cell Research", "token_count": 593, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
active transport form of transport across the cell membrane that requires input of cellular energy - amphipathic describes a molecule that exhibits a difference in polarity between its two ends, resulting in a difference in water solubility - anaphase third stage of mitosis (and meiosis), during which sis...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "KEY TERMS", "token_count": 1471, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
characterized by the linear alignment of sister chromatids in the center of the cell - metaphase plate linear alignment of sister chromatids in the center of the cell, which takes place during metaphase - microfilament the thinnest of the cytoskeletal filaments; composed of actin subunits that function in muscl...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "KEY TERMS", "token_count": 1274, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The internal environmental of a living cell is made up of a fluid, jelly-like substance called cytosol, which consists mainly of water, but also contains various dissolved nutrients and other molecules. The cell contains an array of cellular organelles, each one performing a unique function and helping to maintain the ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 2": "CHAPTER REVIEW", "Header 3": "[3.2 The Cytoplasm and Cellular Organelles](#page-102-0)", "token_count": 381, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The nucleus is the command center of the cell, containing the genetic instructions for all of the materials a cell will make (and thus all of its functions it can perform). The nucleus is encased within a membrane of two interconnected lipid bilayers, side-by-side. This nuclear envelope is studded with protein-lined po...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 2": "CHAPTER REVIEW", "Header 3": "[3.3 The Nucleus and DNA Replication](#page-109-0)", "token_count": 294, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
DNA stores the information necessary for instructing the cell to perform all of its functions. Cells use the genetic code stored within DNA to build proteins, which ultimately determine the structure and function of the cell. This genetic code lies in the particular sequence of nucleotides that make up each gene along ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 2": "CHAPTER REVIEW", "Header 3": "[3.4 Protein Synthesis](#page-115-0)", "token_count": 222, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }

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Certain directional anatomical terms appear throughout this and any other anatomy textbook ([Figure 1.13](#page-33-0)). These terms are essential for describing the relative locations of different body structures. For instance, an anatomist might describe one band of tissue as "inferior to" another or a physician m...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Directional Terms", "token_count": 499, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A section is a two-dimensional surface of a three-dimensional structure that has been cut. Modern medical imaging devices enable clinicians to obtain "virtual sections" of living bodies. We call these scans. Body sections and scans can be correctly interpreted, however, only if the viewer understands the plane alon...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Body Planes", "token_count": 341, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The body maintains its internal organization by means of membranes, sheaths, and other structures that separate compartments. The dorsal (posterior) cavity and the ventral (anterior) cavity are the largest body compartments ([Figure](#page-35-0) [1.15](#page-35-0)). These cavities contain and protect delica...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Body Cavities and Serous Membranes", "token_count": 203, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The posterior (dorsal) and anterior (ventral) cavities are each subdivided into smaller cavities. In the posterior (dorsal) cavity, the cranial cavity houses the brain, and the spinal cavity (or vertebral cavity) encloses the spinal cord. Just as the brain and spinal cord make up a continuous, uninterrupted str...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Subdivisions of the Posterior (Dorsal) and Anterior (Ventral) Cavities", "token_count": 334, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
To promote clear communication, for instance about the location of a patient's abdominal pain or a suspicious mass, health care providers typically divide up the cavity into either nine regions or four quadrants ([Figure 1.16](#page-36-0)). ![](_page_36_Figure_1.jpeg) **Figure 1.16 Regions and Quadrants of the ...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Abdominal Regions and Quadrants", "token_count": 205, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A serous membrane (also referred to a serosa) is one of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities. The parietal layers of the membranes line the walls of the body cavity (pariet- refers to a cavity wall). The visceral layer of the membrane covers the organs (the ...	{ "Header 1": "1.6 \| Anatomical Terminology", "Header 3": "Membranes of the Anterior (Ventral) Body Cavity", "token_count": 437, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Discuss the uses and drawbacks of X-ray imaging - Identify four modern medical imaging techniques and how they are used For thousands of years, fear of the dead and legal sanctions limited the ability of anatomists and physicians to study the internal structures of...	{ "Header 1": "1.7 \| Medical Imaging", "token_count": 260, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
German physicist Wilhelm Röntgen (1845–1923) was experimenting with electrical current when he discovered that a mysterious and invisible "ray" would pass through his flesh but leave an outline of his bones on a screen coated with a metal compound. In 1895, Röntgen made the first durable record of the internal parts of...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "X-Rays", "token_count": 493, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Tomography refers to imaging by sections. Computed tomography (CT) is a noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body ([Figure](#page-38-0) [1.19a](#page-38-0)). The technique was invented in the 1970s a...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "Computed Tomography", "token_count": 583, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant ...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "Magnetic Resonance Imaging", "token_count": 501, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Positron emission tomography (PET) is a medical imaging technique involving the use of so-called radiopharmaceuticals, substances that emit radiation that is short-lived and therefore relatively safe to administer to the body. Although the first PET scanner was introduced in 1961, it took 15 more years before radio...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "Positron Emission Tomography", "token_count": 274, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
abdominopelvic cavity division of the anterior (ventral) cavity that houses the abdominal and pelvic viscera anabolism assembly of more complex molecules from simpler molecules anatomical position standard reference position used for describing locations and directions on the human body anatomy sc...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "KEY TERMS", "token_count": 1572, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Ancient Greek and Latin words are used to build anatomical terms. A standard reference position for mapping the body's structures is the normal anatomical position. Regions of the body are identified using terms such as "occipital" that are more precise than common words and phrases such as "the back of the head." Dire...	{ "Header 1": "1.7 \| Medical Imaging", "Header 3": "[1.6 Anatomical Terminology](#page-31-0)", "token_count": 213, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - Describe the fundamental composition of matter - Identify the three subatomic particles - Identify the four most abundant elements in the body - Explain the relationship between an atom's number of electrons and its relative stability - Distinguish between ionic bon...	{ "Header 1": "Chapter Objectives", "token_count": 398, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Discuss the relationships between matter, mass, elements, compounds, atoms, and subatomic particles - Distinguish between atomic number and mass number - Identify the key distinction between isotopes of the same element - Explain how electrons occupy electron shells ...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "token_count": 270, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Atoms are made up of even smaller subatomic particles, three types of which are important: the proton, neutron, and electron. The number of positively-charged protons and non-charged ("neutral") neutrons, gives mass to the atom, and the number of each in the nucleus of the atom determine the element. The nu...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Atomic Structure and Energy", "token_count": 449, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
An atom of carbon is unique to carbon, but a proton of carbon is not. One proton is the same as another, whether it is found in an atom of carbon, sodium (Na), or iron (Fe). The same is true for neutrons and electrons. So, what gives an element its distinctive properties—what makes carbon so different from sodium or ir...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Atomic Number and Mass Number", "token_count": 725, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Although each element has a unique number of protons, it can exist as different isotopes. An isotope is one of the different forms of an element, distinguished from one another by different numbers of neutrons. The standard isotope of carbon is <sup>12</sup>C, commonly called carbon twelve. <sup>12</sup>C has six p...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Isotopes", "token_count": 496, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The controlled use of radioisotopes has advanced medical diagnosis and treatment of disease. Interventional radiologists are physicians who treat disease by using minimally invasive techniques involving radiation. Many conditions that could once only be treated with a lengthy and traumatic operation can now be treated ...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "Interventional Radiologist", "token_count": 481, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the human body, atoms do not exist as independent entities. Rather, they are constantly reacting with other atoms to form and to break down more complex substances. To fully understand anatomy and physiology you must grasp how atoms participate in such reactions. The key is understanding the behavior of electrons. ...	{ "Header 1": "2.1 \| Elements and Atoms: The Building Blocks of Matter", "Header 3": "The Behavior of Electrons", "token_count": 970, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain the relationship between molecules and compounds - Distinguish between ions, cations, and anions - Identify the key difference between ionic and covalent bonds - Distinguish between nonpolar and polar covalent bonds - Explain how water molecules link via hydr...	{ "Header 1": "2.2 \| Chemical Bonds", "token_count": 398, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Recall that an atom typically has the same number of positively charged protons and negatively charged electrons. As long as this situation remains, the atom is electrically neutral. But when an atom participates in a chemical reaction that results in the donation or acceptance of one or more electrons, the atom will t...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Ions and Ionic Bonds", "token_count": 237, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Potassium (K), for instance, is an important element in all body cells. Its atomic number is 19. It has just one electron in its valence shell. This characteristic makes potassium highly likely to participate in chemical reactions in which it donates one electron. (It is easier for potassium to donate one electron than...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "50 CHAPTER 2 \| THE CHEMICAL LEVEL OF ORGANIZATION", "token_count": 714, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Groups of legislators with completely opposite views on a particular issue are often described as "polarized" by news writers. In chemistry, a polar molecule is a molecule that contains regions that have opposite electrical charges. Polar molecules occur when atoms share electrons unequally, in polar covalent bonds...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Polar Covalent Bonds", "token_count": 230, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
What is true for the bonds is true for the water molecule as a whole; that is, the oxygen region has a slightly negative charge and the regions of the hydrogen atoms have a slightly positive charge. These charges are often referred to as "partial charges" because the strength of the charge is less than one full electro...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Figure 2.10 Polar Covalent Bonds in a Water Molecule", "token_count": 263, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another molecule. In other words, hydrogen bonds always include hydrogen that is already part of a polar molecul...	{ "Header 1": "2.2 \| Chemical Bonds", "Header 3": "Hydrogen Bonds", "token_count": 416, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Chemical reactions require a sufficient amount of energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine you are building a brick wall. The energy...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "The Role of Energy in Chemical Reactions", "token_count": 418, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
You have already learned that chemical energy is absorbed, stored, and released by chemical bonds. In addition to chemical energy, mechanical, radiant, and electrical energy are important in human functioning. - Mechanical energy, which is stored in physical systems such as machines, engines, or the human body, direc...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Forms of Energy Important in Human Functioning", "token_count": 230, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
All chemical reactions begin with a reactant, the general term for the one or more substances that enter into the reaction. Sodium and chloride ions, for example, are the reactants in the production of table salt. The one or more substances produced by a chemical reaction are called the product. In chemical r...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Characteristics of Chemical Reactions", "token_count": 809, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
If chemical reactions are to occur quickly, the atoms in the reactants have to have easy access to one another. Thus, the greater the surface area of the reactants, the more readily they will interact. When you pop a cube of cheese into your mouth, you chew it before you swallow it. Among other things, chewing increase...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Properties of the Reactants", "token_count": 204, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
For two chemicals in nature to react with each other they first have to come into contact, and this occurs through random collisions. Because heat helps increase the kinetic energy of atoms, ions, and molecules, it promotes their collision. But in the body, extremely high heat—such as a very high fever—can damage body ...	{ "Header 1": "2.3 \| Chemical Reactions", "Header 3": "Enzymes and Other Catalysts", "token_count": 438, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Compare and contrast inorganic and organic compounds - Identify the properties of water that make it essential to life - Explain the role of salts in body functioning - Distinguish between acids and bases, and explain their role in pH - Discuss the role of buffers in...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "token_count": 353, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A mixture is a combination of two or more substances, each of which maintains its own chemical identity. In other words, the constituent substances are not chemically bonded into a new, larger chemical compound. The concept is easy to imagine if you think of powdery substances such as flour and sugar; when you stir the...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Water as a Component of Liquid Mixtures", "token_count": 452, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Various mixtures of solutes and water are described in chemistry. The concentration of a given solute is the number of particles of that solute in a given space (oxygen makes up about 21 percent of atmospheric air). In the bloodstream of humans, glucose concentration is usually measured in milligram (mg) per deciliter ...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Concentrations of Solutes", "token_count": 583, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Two types of chemical reactions involve the creation or the consumption of water: dehydration synthesis and hydrolysis. - In dehydration synthesis, one reactant gives up an atom of hydrogen and another reactant gives up a hydroxyl group (OH) in the synthesis of a new product. In the formation of their covalent bond, ...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "The Role of Water in Chemical Reactions", "token_count": 340, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Recall that salts are formed when ions form ionic bonds. In these reactions, one atom gives up one or more electrons, and thus becomes positively charged, whereas the other accepts one or more electrons and becomes negatively charged. You can now define a salt as a substance that, when dissolved in water, dissociates...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Salts", "token_count": 329, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
An acid is a substance that releases hydrogen ions (H<sup>+</sup> ) in solution ([Figure 2.16](#page-68-0)a). Because an atom of hydrogen has just one proton and one electron, a positively charged hydrogen ion is simply a proton. This solitary proton is highly likely to participate in chemical reactions. Strong...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Acids", "token_count": 332, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A base is a substance that releases hydroxyl ions (OH– ) in solution, or one that accepts H<sup>+</sup> already present in solution (see [Figure 2.16](#page-68-0)b). The hydroxyl ions or other base combine with H<sup>+</sup> present to form a water molecule, thereby removing H<sup>+</sup> and reducing the solut...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Bases", "token_count": 212, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The relative acidity or alkalinity of a solution can be indicated by its pH. A solution's pH is the negative, base-10 logarithm of the hydrogen ion (H<sup>+</sup> ) concentration of the solution. As an example, a pH 4 solution has an H<sup>+</sup> concentration that is ten times greater than that of a pH 5 solution...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "The Concept of pH", "token_count": 401, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pH of human blood normally ranges from 7.35 to 7.45, although it is typically identified as pH 7.4. At this slightly basic pH, blood can reduce the acidity resulting from the carbon dioxide (CO2) constantly being released into the bloodstream by the trillions of cells in the body. Homeostatic mechanisms (along with...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Buffers", "token_count": 280, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Excessive acidity of the blood and other body fluids is known as acidosis. Common causes of acidosis are situations and disorders that reduce the effectiveness of breathing, especially the person's ability to exhale fully, which causes a buildup of CO<sup>2</sup> (and H<sup>+</sup> ) in the bloodstream. Acidosis can al...	{ "Header 1": "2.4 \| Inorganic Compounds Essential to Human Functioning", "Header 3": "Acids and Bases", "token_count": 350, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Identify four types of organic molecules essential to human functioning - Explain the chemistry behind carbon's affinity for covalently bonding in organic compounds - Provide examples of three types of carbohydrates, and identify the primary functions of carbohydrate...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "token_count": 207, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
What makes organic compounds ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four electrons in their valence shell, and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence ...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "The Chemistry of Carbon", "token_count": 557, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Carbon's affinity for covalent bonding means that many distinct and relatively stable organic molecules nevertheless readily form larger, more complex molecules. Any large molecule is referred to as macromolecule (macro- = "large"), and the organic compounds in this section all fit this description. However, some m...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Table 2.1", "token_count": 260, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A disaccharide is a pair of monosaccharides. Disaccharides are formed via dehydration synthesis, and the bond linking them is referred to as a glycosidic bond (glyco- = "sugar"). Three disaccharides (shown in [Figure 2.19](#page-73-0)) are important to humans. These are sucrose, commonly referred to as table su...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Disaccharides", "token_count": 312, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Polysaccharides can contain a few to a thousand or more monosaccharides. Three are important to the body ([Figure 2.20](#page-74-0)): - Starches are polymers of glucose. They occur in long chains called amylose or branched chains called amylopectin, both of which are stored in plant-based foods and are relatively...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Polysaccharides", "token_count": 281, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The body obtains carbohydrates from plant-based foods. Grains, fruits, and legumes and other vegetables provide most of the carbohydrate in the human diet, although lactose is found in dairy products. Although most body cells can break down other organic compounds for fuel, all body cells can use glucose. Moreover, n...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Functions of Carbohydrates", "token_count": 342, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A triglyceride is one of the most common dietary lipid groups, and the type found most abundantly in body tissues. This compound, which is commonly referred to as a fat, is formed from the synthesis of two types of molecules ([Figure 2.21](#page-75-0)): - A glycerol backbone at the core of triglycerides, cons...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Triglycerides", "token_count": 795, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As its name suggests, a phospholipid is a bond between the glycerol component of a lipid and a phosphorous molecule. In fact, phospholipids are similar in structure to triglycerides. However, instead of having three fatty acids, a phospholipid is generated from a diglyceride, a glycerol with just two fatty acid cha...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Phospholipids", "token_count": 369, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A steroid compound (referred to as a sterol) has as its foundation a set of four hydrocarbon rings bonded to a variety of other atoms and molecules (see [Figure 2.23b](#page-77-0)). Although both plants and animals synthesize sterols, the type that makes the most important contribution to human structure and fu...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Steroids", "token_count": 230, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Proteins are polymers made up of nitrogen-containing monomers called amino acids. An amino acid is a molecule composed of an amino group and a carboxyl group, together with a variable side chain. Just 20 different amino acids contribute to nearly all of the thousands of different proteins important in human structu...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Microstructure of Proteins", "token_count": 220, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Notice that all amino acids contain both an acid (the carboxyl group) and a base (the amino group) (amine = "nitrogencontaining"). For this reason, they make excellent buffers, helping the body regulate acid–base balance. What distinguishes the 20 amino acids from one another is their variable group, which is referred ...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Figure 2.24 Structure of an Amino Acid", "token_count": 428, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Just as a fork cannot be used to eat soup and a spoon cannot be used to spear meat, a protein's shape is essential to its function. A protein's shape is determined, most fundamentally, by the sequence of amino acids of which it is made ([Figure](#page-80-0) [2.26a](#page-80-0)). The sequence is called the primary s...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Shape of Proteins", "token_count": 913, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
If you were trying to type a paper, and every time you hit a key on your laptop there was a delay of six or seven minutes before you got a response, you would probably get a new laptop. In a similar way, without enzymes to catalyze chemical reactions, the human body would be nonfunctional. It functions only because enz...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Proteins Function as Enzymes", "token_count": 389, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Advertisements for protein bars, powders, and shakes all say that protein is important in building, repairing, and maintaining muscle tissue, but the truth is that proteins contribute to all body tissues, from the skin to the brain cells. Also, certain proteins act as hormones, chemical messengers that help regulate bo...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Other Functions of Proteins", "token_count": 270, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The fourth type of organic compound important to human structure and function are the nucleotides ([Figure 2.28](#page-82-0)). A nucleotide is one of a class of organic compounds composed of three subunits: - one or more phosphate groups - a pentose sugar: either deoxyribose or ribose - a nitrogen-containing ...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Nucleotides", "token_count": 211, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The nucleic acids differ in their type of pentose sugar. Deoxyribonucleic acid (DNA) is nucleotide that stores genetic information. DNA contains deoxyribose (so-called because it has one less atom of oxygen than ribose) plus one phosphate group and one nitrogen-containing base. The "choices" of base for DNA are ade...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Nucleic Acids", "token_count": 523, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When a phosphate group is cleaved from ATP, the products are adenosine diphosphate (ADP) and inorganic phosphate (Pi). This hydrolysis reaction can be written: $$ATP + H_2O \rightarrow ADP + P_i + energy$$ Removal of a second phosphate leaves adenosine monophosphate (AMP) and two phosphate groups. Again, these reac...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "Figure 2.30 Structure of Adenosine Triphosphate (ATP)", "token_count": 242, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
- acid compound that releases hydrogen ions (H<sup>+</sup> ) in solution - activation energy amount of energy greater than the energy contained in the reactants, which must be overcome for a reaction to proceed - adenosine triphosphate (ATP) nucleotide containing ribose and an adenine base that is essential...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "KEY TERMS", "token_count": 1494, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The human body is composed of elements, the most abundant of which are oxygen (O), carbon (C), hydrogen (H) and nitrogen (N). You obtain these elements from the foods you eat and the air you breathe. The smallest unit of an element that retains all of the properties of that element is an atom. But, atoms themselves con...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.1 Elements a](#page-48-1)[nd Atoms: The Building Blocks of Matter](#page-49-0)", "token_count": 294, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Each moment of life, atoms of oxygen, carbon, hydrogen, and the other elements of the human body are making and breaking chemical bonds. Ions are charged atoms that form when an atom donates or accepts one or more negatively charged electrons. Cations (ions with a positive charge) are attracted to anions (ions with a n...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.2 Chemical Bonds](#page-56-0)", "token_count": 221, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Chemical reactions, in which chemical bonds are broken and formed, require an initial investment of energy. Kinetic energy, the energy of matter in motion, fuels the collisions of atoms, ions, and molecules that are necessary if their old bonds are to break and new ones to form. All molecules store potential energy, wh...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.3 Chemical Reactions](#page-61-0)", "token_count": 237, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Inorganic compounds essential to human functioning include water, salts, acids, and bases. These compounds are inorganic; that is, they do not contain both hydrogen and carbon. Water is a lubricant and cushion, a heat sink, a component of liquid mixtures, a byproduct of dehydration synthesis reactions, and a reactant i...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.4 Inorganic Compounds Essential to Human Functioning](#page-64-0)", "token_count": 298, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Organic compounds essential to human functioning include carbohydrates, lipids, proteins, and nucleotides. These compounds are said to be organic because they contain both carbon and hydrogen. Carbon atoms in organic compounds readily share electrons with hydrogen and other atoms, usually oxygen, and sometimes nitrogen...	{ "Header 1": "2.5 \| Organic Compounds Essential to Human Functioning", "Header 3": "[2.5 Organic Compounds Essential to Human Functioning](#page-70-0)", "token_count": 443, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - Describe the structure and function of the cell membrane, including its regulation of materials into and out of the cell - Describe the functions of the various cytoplasmic organelles - Explain the structure and contents of the nucleus, as well as the process of DNA...	{ "Header 1": "Chapter Objectives", "token_count": 743, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The cell membrane is an extremely pliable structure composed primarily of back-to-back phospholipids (a "bilayer"). Cholesterol is also present, which contributes to the fluidity of the membrane, and there are various proteins embedded within the membrane that have a variety of functions. A single phospholipid mo...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Structure and Composition of the Cell Membrane", "token_count": 712, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The lipid bilayer forms the basis of the cell membrane, but it is peppered throughout with various proteins. Two different types of proteins that are commonly associated with the cell membrane are the integral proteins and peripheral protein ([Figure 3.4](#page-95-0)). As its name suggests, an integral protein ...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Membrane Proteins", "token_count": 623, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
One of the great wonders of the cell membrane is its ability to regulate the concentration of substances inside the cell. These substances include ions such as Ca++, Na<sup>+</sup> , K<sup>+</sup> , and Cl– ; nutrients including sugars, fatty acids, and amino acids; and waste products, particularly carbon dioxide (CO2)...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Transport across the Cell Membrane", "token_count": 324, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In order to understand how substances move passively across a cell membrane, it is necessary to understand concentration gradients and diffusion. A concentration gradient is the difference in concentration of a substance across a space. Molecules (or ions) will spread/diffuse from where they are more concentrated...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Passive Transport", "token_count": 1829, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
For all of the transport methods described above, the cell expends no energy. Membrane proteins that aid in the passive transport of substances do so without the use of ATP. During active transport, ATP is required to move a substance across a membrane, often with the help of protein carriers, and usually against its...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Active Transport", "token_count": 1945, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Cystic fibrosis (CF) affects approximately 30,000 people in the United States, with about 1,000 new cases reported each year. The genetic disease is most well known for its damage to the lungs, causing breathing difficulties and chronic lung infections, but it also affects the liver, pancreas, and intestines. Only abou...	{ "Header 1": "3.1 \| The Cell Membrane", "Header 3": "Cell: Cystic Fibrosis", "token_count": 693, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the structure and function of the cellular organelles associated with the endomembrane system, including the endoplasmic reticulum, Golgi apparatus, and lysosomes - Describe the structure and function of mitochondria and peroxisomes - Explain the three compo...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "token_count": 380, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The endoplasmic reticulum (ER) is a system of channels that is continuous with the nuclear membrane (or "envelope") covering the nucleus and composed of the same lipid bilayer material. The ER can be thought of as a series of winding thoroughfares similar to the waterway canals in Venice. The ER provides passages t...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Endoplasmic Reticulum", "token_count": 710, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The Golgi apparatus is responsible for sorting, modifying, and shipping off the products that come from the rough ER, much like a post-office. The Golgi apparatus looks like stacked flattened discs, almost like stacks of oddly shaped pancakes. Like the ER, these discs are membranous. The Golgi apparatus has two dis...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "The Golgi Apparatus", "token_count": 310, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Some of the protein products packaged by the Golgi include digestive enzymes that are meant to remain inside the cell for use in breaking down certain materials. The enzyme-containing vesicles released by the Golgi may form new lysosomes, or fuse with existing, lysosomes. A lysosome is an organelle that contains en...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Lysosomes", "token_count": 373, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A mitochondrion (plural = mitochondria) is a membranous, bean-shaped organelle that is the "energy transformer" of the cell. Mitochondria consist of an outer lipid bilayer membrane as well as an additional inner lipid bilayer membrane ([Figure 3.16](#page-106-0)). The inner membrane is highly folded into windin...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Mitochondria", "token_count": 410, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Like lysosomes, a peroxisome is a membrane-bound cellular organelle that contains mostly enzymes (Figure 3.17). Peroxisomes perform a couple of different functions, including lipid metabolism and chemical detoxification. In contrast to the digestive enzymes found in lysosomes, the enzymes within peroxisomes serve t...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Peroxisomes", "token_count": 770, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The free radical theory on aging was originally proposed in the 1950s, and still remains under debate. Generally speaking, the free radical theory of aging suggests that accumulated cellular damage from oxidative stress contributes to the physiological and anatomical effects of aging. There are two significantly differ...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "Cell: The Free Radical Theory", "token_count": 254, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Much like the bony skeleton structurally supports the human body, the cytoskeleton helps the cells to maintain their structural integrity. The cytoskeleton is a group of fibrous proteins that provide structural support for cells, but this is only one of the functions of the cytoskeleton. Cytoskeletal components are...	{ "Header 1": "3.2 \| The Cytoplasm and Cellular Organelles", "Header 3": "The Cytoskeleton", "token_count": 1000, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the structure and features of the nuclear membrane - List the contents of the nucleus - Explain the organization of the DNA molecule within the nucleus - Describe the process of DNA replication The nucleus is the largest and most prominent of a cell's orga...	{ "Header 1": "3.3 \| The Nucleus and DNA Replication", "token_count": 958, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Like most other cellular organelles, the nucleus is surrounded by a membrane called the nuclear envelope. This membranous covering consists of two adjacent lipid bilayers with a thin fluid space in between them. Spanning these two bilayers are nuclear pores. A nuclear pore is a tiny passageway for the passage o...	{ "Header 1": "3.3 \| The Nucleus and DNA Replication", "Header 3": "Organization of the Nucleus and Its DNA", "token_count": 472, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In order for an organism to grow, develop, and maintain its health, cells must reproduce themselves by dividing to produce two new daughter cells, each with the full complement of DNA as found in the original cell. Billions of new cells are produced in an adult human every day. Only very few cell types in the body do n...	{ "Header 1": "3.3 \| The Nucleus and DNA Replication", "Header 3": "DNA Replication", "token_count": 1088, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain how the genetic code stored within DNA determines the protein that will form - Describe the process of transcription - Describe the process of translation - Discuss the function of ribosomes It was mentioned earlier that DNA provides a "blueprint" for the c...	{ "Header 1": "3.4 \| Protein Synthesis", "token_count": 613, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
DNA is housed within the nucleus, and protein synthesis takes place in the cytoplasm, thus there must be some sort of intermediate messenger that leaves the nucleus and manages protein synthesis. This intermediate messenger is messenger RNA (mRNA), a single-stranded nucleic acid that carries a copy of the genetic c...	{ "Header 1": "3.4 \| Protein Synthesis", "Header 3": "From DNA to RNA: Transcription", "token_count": 958, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Like translating a book from one language into another, the codons on a strand of mRNA must be translated into the amino acid alphabet of proteins. Translation is the process of synthesizing a chain of amino acids called a polypeptide. Translation requires two major aids: first, a "translator," the molecule tha...	{ "Header 1": "3.4 \| Protein Synthesis", "Header 3": "From RNA to Protein: Translation", "token_count": 1124, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the stages of the cell cycle - Discuss how the cell cycle is regulated - Describe the implications of losing control over the cell cycle - Describe the stages of mitosis and cytokinesis, in order So far in this chapter, you have read numerous times of the ...	{ "Header 1": "3.5 \| Cell Growth and Division", "token_count": 354, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A cell grows and carries out all normal metabolic functions and processes in a period called G1 ([Figure 3.30](#page-120-0)). G1 phase (gap 1 phase) is the first gap, or growth phase in the cell cycle. For cells that will divide again, G1 is followed by replication of the DNA, during the S phase. The *S phase...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Interphase", "token_count": 340, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Billions of cells in the human body divide every day. During the synthesis phase (S, for DNA synthesis) of interphase, the amount of DNA within the cell precisely doubles. Therefore, after DNA replication but before cell division, each cell actually contains two copies of each chromosome. Each copy of the chromosome ...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "The Structure of Chromosomes", "token_count": 301, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The mitotic phase of the cell typically takes between 1 and 2 hours. During this phase, a cell undergoes two major processes. First, it completes mitosis, during which the contents of the nucleus are equitably pulled apart and distributed between its two halves. Cytokinesis then occurs, dividing the cytoplasm and c...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Mitosis and Cytokinesis", "token_count": 1624, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As the cell proceeds through its cycle, each phase involves certain processes that must be completed before the cell should advance to the next phase. A checkpoint is a point in the cell cycle at which the cycle can be signaled to move forward or stopped. At each of these checkpoints, different varieties of molecul...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Mechanisms of Cell Cycle Control", "token_count": 348, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Most people understand that cancer or tumors are caused by abnormal cells that multiply continuously. If the abnormal cells continue to divide unstopped, they can damage the tissues around them, spread to other parts of the body, and eventually result in death. In healthy cells, the tight regulation mechanisms of the c...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "The Cell Cycle Out of Control: Implications", "token_count": 243, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Cancer is an extremely complex condition, capable of arising from a wide variety of genetic and environmental causes. Typically, mutations or aberrations in a cell's DNA that compromise normal cell cycle control systems lead to cancerous tumors. Cell cycle control is an example of a homeostatic mechanism that maintains...	{ "Header 1": "3.5 \| Cell Growth and Division", "Header 3": "Cancer Arises from Homeostatic Imbalances", "token_count": 724, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
A stem cell is an unspecialized cell that can divide without limit as needed and can, under specific conditions, differentiate into specialized cells. Stem cells are divided into several categories according to their potential to differentiate. The first embryonic cells that arise from the division of the zygote ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "Stem Cells", "token_count": 556, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When a cell differentiates (becomes more specialized), it may undertake major changes in its size, shape, metabolic activity, and overall function. Because all cells in the body, beginning with the fertilized egg, contain the same DNA, how do the different cell types come to be so different? The answer is analogous to ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "Differentiation", "token_count": 283, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Stem cell research aims to find ways to use stem cells to regenerate and repair cellular damage. Over time, most adult cells undergo the wear and tear of aging and lose their ability to divide and repair themselves. Stem cells do not display a particular morphology or function. Adult stem cells, which exist as a small ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "Stem Cell Research", "token_count": 593, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
active transport form of transport across the cell membrane that requires input of cellular energy - amphipathic describes a molecule that exhibits a difference in polarity between its two ends, resulting in a difference in water solubility - anaphase third stage of mitosis (and meiosis), during which sis...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "KEY TERMS", "token_count": 1471, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
characterized by the linear alignment of sister chromatids in the center of the cell - metaphase plate linear alignment of sister chromatids in the center of the cell, which takes place during metaphase - microfilament the thinnest of the cytoskeletal filaments; composed of actin subunits that function in muscl...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 3": "KEY TERMS", "token_count": 1274, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The internal environmental of a living cell is made up of a fluid, jelly-like substance called cytosol, which consists mainly of water, but also contains various dissolved nutrients and other molecules. The cell contains an array of cellular organelles, each one performing a unique function and helping to maintain the ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 2": "CHAPTER REVIEW", "Header 3": "[3.2 The Cytoplasm and Cellular Organelles](#page-102-0)", "token_count": 381, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The nucleus is the command center of the cell, containing the genetic instructions for all of the materials a cell will make (and thus all of its functions it can perform). The nucleus is encased within a membrane of two interconnected lipid bilayers, side-by-side. This nuclear envelope is studded with protein-lined po...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 2": "CHAPTER REVIEW", "Header 3": "[3.3 The Nucleus and DNA Replication](#page-109-0)", "token_count": 294, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
DNA stores the information necessary for instructing the cell to perform all of its functions. Cells use the genetic code stored within DNA to build proteins, which ultimately determine the structure and function of the cell. This genetic code lies in the particular sequence of nucleotides that make up each gene along ...	{ "Header 1": "3.6 \| Cellular Differentiation", "Header 2": "CHAPTER REVIEW", "Header 3": "[3.4 Protein Synthesis](#page-115-0)", "token_count": 222, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }