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an amino group, a carboxyl group, a hydrogen, and an R group or side chain is attached; the R group is different for the most common 20 amino acids beta-pleated sheet (β-pleated) secondary structure found in proteins in which “pleats” are formed by hydrogen bonding between atoms on the backbone of the polypeptide chai... |
by the body; the numbering of the carbon omega starts from the methyl end or the end that is farthest from the carboxylic end peptide bond bond formed between two amino acids by a dehydration reaction phosphodiester linkage covalent chemical bond that holds together the polynucleotide chains, with a phosphate group Th... |
lipids transcription process through which messenger RNA forms on a template of DNA transfer RNA (tRNA) RNA that carries activated amino acids to the site of protein synthesis on the ribosome translation process through which RNA directs the formation of protein triacylglycerol (also, triglyceride) fat molecule; consi... |
that are formed as a result of dehydration reactions, forming disaccharides and polysaccharides with the elimination of a water molecule for each bond formed. Glucose, galactose, and fructose are common monosaccharides, whereas common disaccharides include lactose, maltose, and sucrose. Starch and glycogen, examples o... |
that is linked to an amino group, a carboxyl group, a hydrogen atom, and an R group or side chain. There are 20 commonly occurring amino acids, each of which differs in the R group. Each amino acid is linked to its neighbors by a peptide bond. A long chain of amino acids is known as a polypeptide. Proteins are organiz... |
omers b. polymers c. carbohydrates only d. water only b. protein c. RNA d. triglyceride 8. What is an example of a monosaccharide? 2. What is removed during the formation of nucleic acid polymers? a. carbon b. hydroxyl groups c. phosphates d. amino acids 3. During the breakdown of polymers, which of the following react... |
fat serves as an animal’s major form of energy storage? a. cholesterol b. glycerol c. phospholipid d. triglycerides 15. Which hormones are made from cholesterol? a. estradiol and testosterone b. insulin and growth hormone c. progesterone and glucagon d. prolactin and thyroid hormone a. mRNA transport b. production of ... |
chaperones c. disaccharides d. nucleotides 28. Where is the linkage made that combines two amino acids? a. between the R group of one amino acid and the R group of the second b. between the carboxyl group of one amino acid and the amino group of the other c. between the 6 carbon of both amino acids d. between the nitr... |
of nucleic acids? b. c. in the nucleus in the cytoplasm d. on ribosomes a. nitrogenous bases b. nucleotides c. peptides d. sugars CRITICAL THINKING QUESTIONS 39. The word hydrolysis is defined as the lysis of water. How does this apply to polymers? 40. What role do electrons play in dehydration synthesis and hydrolysi... |
humans to digest food that contains cellulose? a. There is no energy available in fiber. b. An inactive form of cellulase in human digestive tract renders it undigested and removes it as waste. c. The acidic environment in the human stomach makes it impossible to break the bonds in cellulose. d. Human digestive enzyme... |
cules 137 a. Trans fat is produced by the hydrogenation of oil that makes it more saturated and isomerized. It increases LDL amounts. b. The dehydrogenation of oil forms the trans fat, which contains single bonds in its structure. This increases HDL in the body and has been banned. c. Trans fat is produced by dehydroge... |
, which is a lipid and also a steroid, functions here. c. Glycogen, which is a multi-branched polysaccharide of glucose, is the compound. d. Phosphatidylcholine that is a phospholipid with a choline head group, which serves the functions. 50. What part of cell membranes gives flexibility to the structure? a. carbohydra... |
specific amino acids to a developing protein strand. microRNA (miRNA) regulates the expression of the mRNA strand. c. mRNA regulates the expression of the miRNA strand. rRNA are found in ribosomes. tRNA transfers specific amino acids to a developing protein strand. miRNA is a single stranded transcript of DNA. d. mRNA... |
little now? This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 3 | Biological Macromolecules 139 a. Hydrogen gas is so light with a molecular weight of 1 that the excess diffused into space over time and is now absent from the atmosphere. b. Hydrogen combined with ammonia to make a... |
unsaturated fats do not. b. Saturated and unsaturated fats have stable configurations, while trans fats are transient. c. Unsaturated fats and trans fats have some double bonded carbon atoms, while saturated fats do not. d. Unsaturated and trans fats are the same; the fatty acids are just found on opposite sides of a ... |
utamine-lysine-glutamate. You insert arginine between the leucine and methionine. What effect would this have on the segment? a. Arginine is a negatively charged amino acid and could attach to the glutamate at the end of the segment b. Inserting arginine places a positively charged amino acid in a portion that is non-p... |
is a short segment of DNA using the slash symbol ( / ) to separate the codons for easy viewing: ATC/GTT/GAA/CTG/TAG/GAT/AAA d. The arginine could attach to the lysine and bend the protein chain at this point. A change has occurred in the segment resulting in the following: 70. What would happen if even one amino acid ... |
4, two molecules of pyruvic acid are produced. Several enzymes in the cell are involved in converting glucose to pyruvic acid. These enzymes are proteins whose amino acid sequences provide these functions. This protein structure is information that was inherited from the cell’s parent, and is stored in deoxyribonuclei... |
through water. These measurements were carried out at four different temperatures. One type of membrane was obtained from the cells in the eyeball of a calf (lens lipid). Synthetic membranes composed of palmitic acid with cholesterol (POPC/CHOL) and without cholesterol (POPC) were also used. The results from these exp... |
. Fluidity is also affected by temperature. Measurements of the speed of movement of oxygen This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 3 | Biological Macromolecules 143 are distributed unequally. Polarity in a molecule also is caused by charge asymmetry. Life on Earth has ev... |
pairs; rank them and provide your reasoning. In an amino acid, the atoms attached to the α carbon are 144 called the R group. Chapter 3 | Biological Macromolecules Figure 3.43 Interactions between R groups of a polypeptide give threedimensional structure to the one-dimensional, linear sequence of amino acids in a poly... |
weaker hydrogen bonds, chemical bonds within the molecules. Demonstrating an understanding of the replication of DNA requires the ability to explain how the two polymer strands of the double helix interact and grow. To retrieve information from DNA, the strands must be separated. The proteins that perform that task in... |
work by Anthony D'Onofrio, William H. Fowle, Eric J. Stewart, and Kim Lewis of the Lewis Lab at Northeastern University; scale-bar data from Matt Russell) Chapter Outline 4.1: Studying Cells 4.2: Prokaryotic Cells 4.3: Eukaryotic Cells 4.4: The Endomembrane System and Proteins 4.5: Cytoskeleton 4.6: Connections betwee... |
microscopy and electron microscopy? • What is the cell theory? Connection for AP® Courses A cell is the smallest unit of a living thing. A living thing, whether made of one cell (like bacteria) or many cells (like a human), is called an organism. Thus, cells are the basic building blocks of all organisms. Several cell... |
(abbreviated as eight μm) in diameter; the head of a pin of is about two thousandths of a meter (two mm) in diameter. That means about 250 red blood cells could fit on the head of a pin. Most student microscopes are classified as light microscopes (Figure 4.2a). Visible light passes and is bent through the lens system... |
a transmission electron microscope, the electron beam penetrates the cell and provides details of a cell’s internal structures. As you might imagine, electron microscopes are significantly more bulky and expensive than light microscopes. (a) (b) Figure 4.3 (a) These Salmonella bacteria appear as tiny purple dots when ... |
more cells, the cell is the basic unit of life, and new cells arise from existing cells. Rudolf Virchow later made important contributions to this theory. This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 4 | Cell Structure 151 Have you ever heard of a medical test called a Pap sm... |
all living organisms, from bacteria to humans, are composed of cells, the smallest units of living matter. Often too small to be seen without a microscope, cells come in all sizes and shapes, and their small size allows for a large surface area-to-volume ratio that enables a more efficient exchange of nutrients and wa... |
of geological, physical, chemical, and biological data that reveal early Earth conditions. Essential Knowledge 2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. Science Practice Learning Objective 2.2 The student can apply mathematical routines to quantities that d... |
a cell membrane, and a cell wall. The other structures shown are present in some, but not all, bacteria. While the Earth is approximately 4.6 billion years old, the earliest fossil evidence for life are of microbial mats that date back to 3.5 billion years. What type of evidence for life was most likely found in a 3.5... |
Environmental microbiologists may look for new ways to use specially selected or genetically engineered microbes for the removal of pollutants from soil or groundwater, as well as hazardous elements from contaminated sites. These uses of microbes are called bioremediation technologies. Microbiologists can also work in... |
way is to develop organelles that perform specific tasks. These adaptations lead to the development of more sophisticated cells called eukaryotic cells. Besides the volume of the cell, the size of the cell is also important for survival. As mentioned before, most cells are approximately spherical in shape. This is bec... |
and CO2 among them. Think About It Which of the following cells would likely exchange nutrients and wastes with its environment more efficiently: a spherical cell with a diameter of 5 μm or a cubed-shaped cell with a side length of 7μm? Provide a quantitative justification for your answer based on surface area-to-volu... |
, and they are equipped to break down hydrogen peroxide formed from these reactions without letting it into the cytoplasm where it can cause damage. Vesicles and vacuoles store substances, and in plant cells, the central vacuole stores pigments, salts, minerals, nutrients, proteins, and degradation enzymes and helps ma... |
A 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. 2.14 The student is able to use representations and models to describe differences in prokaryotic and eukaryotic cells. Biological systems interact, and these systems and their interactions pos... |
organelles, let’s first examine two important components of the cell: the plasma membrane and the cytoplasm. This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 4 | Cell Structure 159 (a) (b) Figure 4.8 These figures show the major organelles and other cell components of (a) a typic... |
malnutrition, cramping, and diarrhea. Patients suffering from celiac disease must follow a gluten-free diet. Figure 4.10 Microvilli, shown here as they appear on cells lining the small intestine, increase the surface area available for absorption. These microvilli are only found on the area of the plasma membrane that... |
outer membranes of the nuclear envelope are phospholipid bilayers. The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm. The nucleoplasm is the semi-solid fluid inside the nucleus, where we find the chromatin and the nucleolus. Chromat... |
ulum and the outer membrane of the nuclear envelope (Figure 4.8). Electron microscopy has shown us that ribosomes, which are large complexes of protein and RNA, consist of two subunits, aptly called large and small (Figure 4.13). Ribosomes receive their “orders” for protein synthesis from the nucleus where the DNA is t... |
accompanied by the production of lactic acid. Mitochondria are oval-shaped, double membrane organelles (Figure 4.14) that have their own ribosomes and DNA. Each membrane is a phospholipid bilayer embedded with proteins. The inner layer has folds called cristae. The area surrounded by the folds is called the mitochondr... |
associated with the MTOC: a complex called the centrosome. Animal cells each have a centrosome and lysosomes, whereas most plant cells do not. Plant cells have a cell wall, chloroplasts and other specialized plastids, and a large central vacuole, whereas animal cells do not. The Centrosome The centrosome is a microtub... |
that protects the cell, provides structural support, and gives shape to the cell. Fungal and protistan cells also have cell walls. While the chief component of prokaryotic cell walls is peptidoglycan, the major organic molecule in the plant cell wall is cellulose (Figure 4.16), a polysaccharide made up of glucose unit... |
single circular chromosome. The chloroplasts contain a green pigment called chlorophyll, which captures the light energy that drives the reactions of photosynthesis. Like plant cells, photosynthetic protists also have chloroplasts. Some bacteria perform photosynthesis, but their chlorophyll is not relegated to an orga... |
, we mentioned vacuoles as essential components of plant cells. If you look at Figure 4.8b, you will see that plant cells each have a large central vacuole that occupies most of the area of the cell. The central vacuole plays a key role in regulating the cell’s concentration of water in changing environmental condition... |
elles that allow for compartmentalization of functions. The plasma membrane is a phospholipid bilayer embedded with proteins. The nucleus’s nucleolus is the site of ribosome assembly. Ribosomes are either found in the cytoplasm or attached to the cytoplasmic side of the plasma membrane or endoplasmic reticulum. They pe... |
engages in the detoxification of medications and poisons; and stores calcium ions. Lysosomes digest macromolecules, recycle worn-out organelles, and destroy pathogens. Just like your body uses different organs that work together, cells use these organelles interact to perform specific functions. For example, proteins ... |
APLO 4.6] The Endoplasmic Reticulum The endomembrane system (endo = “within”) is a group of membranes and organelles (Figure 4.18) in eukaryotic cells that works together to modify, package, and transport lipids and proteins. It includes the nuclear envelope, lysosomes, and vesicles, which we’ve already mentioned, and ... |
/1.6 Chapter 4 | Cell Structure 169 The endoplasmic reticulum (ER) (Figure 4.18) is a series of interconnected membranous sacs and tubules that collectively modifies proteins and synthesizes lipids. However, these two functions are performed in separate areas of the ER: the rough ER and the smooth ER, respectively. The... |
You can watch an excellent animation of the endomembrane system here (http://openstaxcollege.org/l/endomembrane). How do the nucleus and the endomembrane system work together for protein synthesis? a. The endomembrane system processes and ships proteins specified by the nucleus. In the nucleus, DNA is used to make RNA... |
activity of the heart), a chest X-ray to see whether the heart is enlarged, and other tests. If heart failure is diagnosed, the cardiologist will typically prescribe appropriate medications and recommend a reduction in table salt intake and a supervised exercise program. failure. Cardiologists can make a diagnosis of ... |
has the additional role of synthesizing polysaccharides, some of which are incorporated into the cell wall and some of which are used in other parts of the cell. Geneticist Many diseases arise from genetic mutations that prevent the synthesis of critical proteins. One such disease is Lowe disease (also called oculocer... |
off from the plasma membrane and becomes a vesicle. The vesicle fuses with a lysosome. The lysosome’s hydrolytic enzymes then destroy the pathogen (Figure 4.21). Figure 4.21 A macrophage has engulfed (phagocytized) a potentially pathogenic bacterium which then fuses with a lysosome within the cell to destroy the patho... |
nucleus and other organelles in place, moves vesicles through the cell, and pulls replicated chromosomes to the poles of a dividing cell. These protein elements are also integral to the movement of centrioles, flagella, and cilia. The information presented and the examples highlighted in the section support concepts a... |
elles in place. Of the three types of protein fibers in the cytoskeleton, microfilaments are the narrowest. They function in cellular movement, have a diameter of about 7 nm, and are made of two intertwined strands of a globular protein called actin (Figure 4.23). For this reason, microfilaments are also known as actin... |
fewer white blood cells. Intermediate Filaments Intermediate filaments are made of several strands of fibrous proteins that are wound together (Figure 4.24). These elements of the cytoskeleton get their name from the fact that their diameter, 8 to 10 nm, is between those of microfilaments and microtubules. Figure 4.24... |
the cell has just one flagellum or a few flagella. When cilia (singular = cilium) are present, however, many of them extend along the entire surface of the plasma membrane. They are short, hair-like structures that are used to move entire cells (such as paramecia) or substances along the outer surface of the cell (for... |
that houses DNA and directs synthesis of ribosomes and proteins Ribosomes Protein synthesis Mitochondria ATP production/cellular respiration Peroxisomes Oxidizes and thus breaks down fatty acids and amino acids, and detoxifies poisons Vesicles and vacuoles Storage and transport; digestive function in plant cells Centr... |
questions: • What are the components of the extracellular matrix? • What are the roles of tight junctions, gap junctions, and plasmodesmata in allowing cells to exchange materials with the environment and communicate with other cells? Connection for AP® Courses With the exception of gap junctions between animal cells ... |
plasma membranes. When a molecule within the matrix binds to the receptor, it changes the molecular structure of the receptor. The receptor, in turn, changes the conformation of the microfilaments positioned just inside the plasma membrane. These conformational changes induce chemical signals inside the cell that reac... |
called claudins and occludins). Figure 4.29 Tight junctions form watertight connections between adjacent animal cells. Proteins create tight junction adherence. (credit: modification of work by Mariana Ruiz Villareal) This tight adherence prevents materials from leaking between the cells; tight junctions are typically... |
a cell, work through the steps of this interactive assignment (http://openstaxcollege.org/l/microscopy_lab). What are two similarities and two differences between plant and animal cells that can be seen under a microscope? a. Plant cells have cell walls which provide structure to the plant and also chloroplasts which ... |
suspended in the gel-like cytosol, the cytoskeleton, and various chemicals cytoskeleton network of protein fibers that collectively maintain the shape of the cell, secure some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable unicellular organisms to move independently ... |
; it helps the cell resist compression, provides a track along which vesicles move through the cell, pulls replicated chromosomes to opposite ends of a dividing cell, and is the structural element of centrioles, flagella, and cilia mitochondria (singular = mitochondrion) cellular organelles responsible for carrying out... |
storage and transport vesicle small, membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and the membranes of the endoplasmic reticulum and Golgi apparatus CHAPTER SUMMARY 4.1 Studying Cells A cell is the smallest unit of life. Most cells are ... |
icles and vacuoles are storage and transport compartments. In plant cells, vacuoles also help break down macromolecules. Animal cells also have a centrosome and lysosomes. The centrosome has two bodies perpendicular to each other, the centrioles, and has an unknown purpose in cell division. Lysosomes are the digestive ... |
junctions, desmosomes, and gap junctions. Plant cells are connected and communicate with each other via plasmodesmata. When protein receptors on the surface of the plasma membrane of an animal cell bind to a substance in the extracellular matrix, a chain of reactions begins that changes activities taking place within ... |
organisms. c. Prokaryotic and eukaryotic cells are surrounded by a plasma membrane. d. Viruses replicate. 7. In order to obtain some materials and remove waste, what process is used by prokaryotes? lack a nucleus. c. Both cells have DNA but prokaryotic cells lack a cell membrane. d. Both cells have a cell membrane but... |
, the genetic material, in an animal cell? a. in the centriole b. only in the mitochondria c. in the mitochondria and the nucleus 17. Which of the following is most likely to have the greatest concentration of smooth endoplasmic reticulum (SER)? a. a cell that secretes enzymes b. a cell that destroys pathogens c. a cel... |
. tight, rivet-like regions in the membranes of adjacent cells d. a tight knitting of membranes 25. Some animal cells produce extensive extracellular matrix. You would expect their ribosomes to synthesize large amounts of which of the following proteins? CRITICAL THINKING QUESTIONS 27. Which element of the cell theory ... |
ochondria participate in the Calvin cycle/ light independent reactions of photosynthesis. d. Mitochondria are required to break down sugars and other materials for energy. This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 4 | Cell Structure 189 30. In what situation, or situations,... |
a rigid cell wall to prevent the influx of waste material. 34. Bacteria do not have organelles; yet, the same reactions that take place on the mitochondria inner membrane, the phosphorylation of ADP to ATP, and chloroplasts, photosynthesis, take place in bacteria. Where do these reactions take place? a. These reaction... |
a separate organelle. 37. What happens to the proteins that are synthesized on free ribosomes in the cytoplasm? Do they go through the Golgi apparatus? a. These proteins move through the Golgi apparatus and enter in the nucleus. b. These proteins go through the Golgi apparatus and remain in the cytosol. c. The protein... |
such as the one involved in Ehlers-Danlos syndrome, and the individual produces defective collagen, how would it affect coagulation? a. The syndrome affects the clotting factors and platelet aggregation. b. The disease leads to hyper-coagulation of blood. c. Coagulation is not affected because collagen is not required... |
sphere? a. The sphere will have a higher surface area than the cube. b. The sphere will have a higher volume than the cube. c. The sphere will have a higher surface area-to- volume ratio than the cube. d. Their surface area-to-volume ratios will be equal. e. The sphere will have a lower surface area-to- volume ratio t... |
ium. What is the main argument to justify the classification? a. This organism shows simple diffusion for the uptake of nutrients and is thus classified as a bacterium. b. This organism does not show presence of any cell organelles, and thus is classified as a bacterium. c. the existence of these organisms in long chai... |
plants have common ancestors based on your observations. 63. What conserved core processes are common to both animals and plants? Construct an explanation of the differences based on the selective advantages provided in different environments. 64. Louis Sullivan described architectural design as “form follows function... |
blood cell? • What is the range of blood vessel diameters in adult humans? • What is the range of red blood cell size in vertebrates? • What is the average lifetime of a human red blood cell? • How can you show how cell production is stimulated using examples from particular systems? • How is cell death controlled? • ... |
, Grand Central Station functions with a high level of organization: People and objects move from one location to another, they cross or are contained within certain boundaries, and they provide a constant flow as part of larger activity. Analogously, a plasma membrane’s functions involve movement within the cell and a... |
ids (which we studied in previously) form a bilayer; the hydrophobic, fatty acid tails are in contact with each other and hydrophilic portions of the phospholipids are oriented toward the aqueous internal and external environments. Several types of proteins with different functions stud the membrane. Integral proteins ... |
or across enduring understandings and/or big ideas. This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 5 | Structure and Function of Plasma Membranes 197 Learning Objective 2.11 The student is able to construct models that connect the movement of molecules across membrane with membr... |
, rather than a single, layer. A new model that better explains both the microscopic observations and the function of that plasma membrane was proposed by S.J. Singer and Garth L. Nicolson in 1972. The explanation proposed by Singer and Nicolson is called the fluid mosaic model. The model has evolved somewhat over time... |
attached to proteins, forming glycoproteins, or attached to lipids, forming glycolipids. Phospholipids The main fabric of the membrane is composed of amphiphilic, phospholipid molecules. The hydrophilic or “water-loving” areas of these molecules (which look like a collection of balls in an artist’s rendition of the mo... |
rophilic heads facing out. In this way, they form a lipid This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 5 | Structure and Function of Plasma Membranes 199 bilayer—a barrier composed of a double layer of phospholipids that separates the water and other materials on one side of t... |
(credit: “Foobar”/Wikimedia Commons) Peripheral proteins are found on the exterior and interior surfaces of membranes, attached either to integral proteins or to phospholipids. Peripheral proteins, along with integral proteins, may serve as enzymes, as structural attachments for the fibers of the cytoskeleton, or as p... |
of cells give many viruses an opportunity for infection. HIV and hepatitis viruses infect only specific organs or cells in the human body. HIV is able to penetrate the plasma membranes of a subtype of lymphocytes called T-helper cells, as well as some monocytes and central nervous system cells. The hepatitis virus att... |
molecules. These resemble the separate, multicolored tiles of a mosaic picture, and they float, moving somewhat with respect to one another. The membrane is not like a balloon, however, that can expand and contract; rather, it is fairly rigid and can burst if penetrated or if a cell takes in too much water. However, b... |
required for larger molecules. c. The plasma membrane is permeable to all polar molecules, but a transport protein is required. d. The plasma membrane is selectively permeable to all polar molecules and a transport protein is never required for them. Animals have an additional membrane constituent that assists in main... |
will not reject a transplanted organ. Some immunologists work to understand natural immunity and the effects of a person’s environment on it. Others work on questions about how the immune system affects the development of certain chronic diseases. To work as an immunologist, a PhD or MD is required. In addition, immun... |
When the concentrations of solute are equal on both sides of the membrane (isotonic), no net movement of water into or out of the cell occurs. Living organisms have evolved a variety of ways to maintain osmotic balance; for example, marine fish secrete excess salt through the gills to maintain dynamic homeostasis. Inf... |
lose this selectivity, the cell would no longer be able to sustain itself, and it would be destroyed. Some cells require larger amounts of specific substances than do other cells; they must have a way of obtaining these materials from extracellular fluids. This may happen passively, as certain materials move back and ... |
readily transported into the body’s tissues and organs. Similarly, molecules of oxygen and carbon dioxide have no charge and so pass through membranes by simple diffusion. Polar substances present problems for the membrane. While some polar molecules connect easily with the outside of a cell, they cannot readily pass ... |
will tend to move into any space available to it until it is evenly distributed throughout it. After a substance has diffused completely through a space, removing its concentration gradient, molecules will still move around in the space, but there will be no net movement of the number of molecules from one area to ano... |
Function of Plasma Membranes 207 center of the cell, respectively. Therefore, cells must either be small in size, as in the case of many prokaryotes, or be flattened, as with many single-celled eukaryotes. A variation of diffusion is the process of filtration. In filtration, material moves according to its concentrati... |
allow water to pass through the membrane at a very high rate. Figure 5.9 Facilitated transport moves substances down their concentration gradients. They may cross the plasma membrane with the aid of channel proteins. (credit: modification of work by Mariana Ruiz Villareal) Channel proteins are either open at all times... |
iz Villareal) An example of this process occurs in the kidney. Glucose, water, salts, ions, and amino acids needed by the body are filtered in one part of the kidney. This filtrate, which includes glucose, is then reabsorbed in another part of the kidney. Because there are only a finite number of carrier proteins for g... |
side of the membrane. Figure 5.11 In osmosis, water always moves from an area of higher water concentration to one of lower concentration. In the diagram shown, the solute cannot pass through the selectively permeable membrane, but the water can. To illustrate this, imagine two full glasses of water. One has a single ... |
from taking on too much water. However, red blood cells lack these controls, making them ideal for osmolarity studies. This is an important consideration for clinicians delivering drugs intravenously. How would the drug have to be formulated, in terms of osmolarity, to prevent red blood cells from undergoing hemolysis... |
.) It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell. In this situation, water will follow its concentration gradient and enter the cell. Hypertonic Solutions As for a hypertonic solution, the prefix hyper- refers to the extracellular fluid having a higher... |
x.org/content/col12078/1.6 Chapter 5 | Structure and Function of Plasma Membranes 211 A red blood cell will burst, or lyse, when it swells beyond the plasma membrane’s capability to expand. Remember, the membrane resembles a mosaic, with discrete spaces between the molecules composing it. If the cell swells, and the sp... |
all living things. For example, paramecia and amoebas, which are protists that lack cell walls, have contractile vacuoles. This vesicle collects excess water from the cell and pumps it out, keeping the cell from lysing as it takes on water from its environment (Figure 5.15). 212 Chapter 5 | Structure and Function of P... |
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