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cell theory : see unified cell theory | https://openstax.org/books/biology/pages/4-key-terms |
cell wall : rigid cell covering made of various molecules that protects the cell, provides structural support, and gives shape to the cell | https://openstax.org/books/biology/pages/4-key-terms |
central vacuole : large plant cell organelle that regulates the cellâs storage compartment, holds water, and plays a significant role in cell growth as the site of macromolecule degradation | https://openstax.org/books/biology/pages/4-key-terms |
centrosome : region in animal cells made of two centrioles | https://openstax.org/books/biology/pages/4-key-terms |
chlorophyll : green pigment that captures the light energy that drives the light reactions of photosynthesis | https://openstax.org/books/biology/pages/4-key-terms |
chloroplast : plant cell organelle that carries out photosynthesis | https://openstax.org/books/biology/pages/4-key-terms |
chromatin : protein-DNA complex that serves as the building material of chromosomes | https://openstax.org/books/biology/pages/4-key-terms |
chromosome : structure within the nucleus that is made up of chromatin that contains DNA, the hereditary material | https://openstax.org/books/biology/pages/4-key-terms |
cilium : (plural = cilia) short, hair-like structure that extends from the plasma membrane in large numbers and is used to move an entire cell or move substances along the outer surface of the cell | https://openstax.org/books/biology/pages/4-key-terms |
cytoplasm : entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals | https://openstax.org/books/biology/pages/4-key-terms |
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 | https://openstax.org/books/biology/pages/4-key-terms |
cytosol : gel-like material of the cytoplasm in which cell structures are suspended | https://openstax.org/books/biology/pages/4-key-terms |
desmosome : linkages between adjacent epithelial cells that form when cadherins in the plasma membrane attach to intermediate filaments | https://openstax.org/books/biology/pages/4-key-terms |
electron microscope : an instrument that magnifies an object using a beam of electrons passed and bent through a lens system to visualize a specimen | https://openstax.org/books/biology/pages/4-key-terms |
endomembrane system : group of organelles and membranes in eukaryotic cells that work together modifying, packaging, and transporting lipids and proteins | https://openstax.org/books/biology/pages/4-key-terms |
endoplasmic reticulum (ER) : series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids | https://openstax.org/books/biology/pages/4-key-terms |
eukaryotic cell : cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs | https://openstax.org/books/biology/pages/4-key-terms |
extracellular matrix : material (primarily collagen, glycoproteins, and proteoglycans) secreted from animal cells that provides mechanical protection and anchoring for the cells in the tissue | https://openstax.org/books/biology/pages/4-key-terms |
flagellum : (plural = flagella) long, hair-like structure that extends from the plasma membrane and is used to move the cell | https://openstax.org/books/biology/pages/4-key-terms |
gap junction : channel between two adjacent animal cells that allows ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate | https://openstax.org/books/biology/pages/4-key-terms |
Golgi apparatus : eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution | https://openstax.org/books/biology/pages/4-key-terms |
intermediate filament : cytoskeletal component, composed of several intertwined strands of fibrous protein, that bears tension, supports cell-cell junctions, and anchors cells to extracellular structures | https://openstax.org/books/biology/pages/4-key-terms |
light microscope : an instrument that magnifies an object using a beam visible light passed and bent through a lens system to visualize a specimen | https://openstax.org/books/biology/pages/4-key-terms |
lysosome : organelle in an animal cell that functions as the cellâs digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles | https://openstax.org/books/biology/pages/4-key-terms |
microfilament : narrowest element of the cytoskeleton system; it provides rigidity and shape to the cell and enables cellular movements | https://openstax.org/books/biology/pages/4-key-terms |
microscope : an instrument that magnifies an object | https://openstax.org/books/biology/pages/4-key-terms |
microtubule : widest element of the cytoskeleton system; 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 | https://openstax.org/books/biology/pages/4-key-terms |
mitochondria : (singular = mitochondrion) cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cellâs main energy-carrying molecule | https://openstax.org/books/biology/pages/4-key-terms |
nuclear envelope : double-membrane structure that constitutes the outermost portion of the nucleus | https://openstax.org/books/biology/pages/4-key-terms |
nucleoid : central part of a prokaryotic cell in which the chromosome is found | https://openstax.org/books/biology/pages/4-key-terms |
nucleolus : darkly staining body within the nucleus that is responsible for assembling the subunits of the ribosomes | https://openstax.org/books/biology/pages/4-key-terms |
nucleoplasm : semi-solid fluid inside the nucleus that contains the chromatin and nucleolus | https://openstax.org/books/biology/pages/4-key-terms |
nucleus : cell organelle that houses the cellâs DNA and directs the synthesis of ribosomes and proteins | https://openstax.org/books/biology/pages/4-key-terms |
organelle : compartment or sac within a cell | https://openstax.org/books/biology/pages/4-key-terms |
peroxisome : small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons | https://openstax.org/books/biology/pages/4-key-terms |
plasma membrane : phospholipid bilayer with embedded (integral) or attached (peripheral) proteins, and separates the internal content of the cell from its surrounding environment | https://openstax.org/books/biology/pages/4-key-terms |
plasmodesma : (plural = plasmodesmata) channel that passes between the cell walls of adjacent plant cells, connects their cytoplasm, and allows materials to be transported from cell to cell | https://openstax.org/books/biology/pages/4-key-terms |
prokaryote : unicellular organism that lacks a nucleus or any other membrane-bound organelle | https://openstax.org/books/biology/pages/4-key-terms |
ribosome : cellular structure that carries out protein synthesis | https://openstax.org/books/biology/pages/4-key-terms |
rough endoplasmic reticulum (RER) : region of the endoplasmic reticulum that is studded with ribosomes and engages in protein modification and phospholipid synthesis | https://openstax.org/books/biology/pages/4-key-terms |
smooth endoplasmic reticulum (SER) : region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface and synthesizes carbohydrates, lipids, and steroid hormones; detoxifies certain chemicals (like pesticides, preservatives, medications, and environmental pollutants), and stores calcium ions | https://openstax.org/books/biology/pages/4-key-terms |
tight junction : firm seal between two adjacent animal cells created by protein adherence | https://openstax.org/books/biology/pages/4-key-terms |
unified cell theory : a biological concept that states that all organisms are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells | https://openstax.org/books/biology/pages/4-key-terms |
vacuole : membrane-bound sac, somewhat larger than a vesicle, which functions in cellular storage and transport | https://openstax.org/books/biology/pages/4-key-terms |
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 | https://openstax.org/books/biology/pages/4-key-terms |
The modern understanding of the plasma membrane is referred to as the fluid mosaic model. The plasma membrane is composed of a bilayer of phospholipids, with their hydrophobic, fatty acid tails in contact with each other. The landscape of the membrane is studded with proteins, some of which span the membrane. Some of t... | https://openstax.org/books/biology/pages/5-chapter-summary |
The passive forms of transport, diffusion and osmosis, move materials of small molecular weight across membranes. Substances diffuse from areas of high concentration to areas of lower concentration, and this process continues until the substance is evenly distributed in a system. In solutions containing more than one s... | https://openstax.org/books/biology/pages/5-chapter-summary |
In living systems, diffusion of substances into and out of cells is mediated by the plasma membrane. Some materials diffuse readily through the membrane, but others are hindered, and their passage is made possible by specialized proteins, such as channels and transporters. The chemistry of living things occurs in aqueo... | https://openstax.org/books/biology/pages/5-chapter-summary |
The combined gradient that affects an ion includes its concentration gradient and its electrical gradient. A positive ion, for example, might tend to diffuse into a new area, down its concentration gradient, but if it is diffusing into an area of net positive charge, its diffusion will be hampered by its electrical gra... | https://openstax.org/books/biology/pages/5-chapter-summary |
Active transport methods require the direct use of ATP to fuel the transport. Large particles, such as macromolecules, parts of cells, or whole cells, can be engulfed by other cells in a process called phagocytosis. In phagocytosis, a portion of the membrane invaginates and flows around the particle, eventually pinchin... | https://openstax.org/books/biology/pages/5-chapter-summary |
active transport : method of transporting material that requires energy | https://openstax.org/books/biology/pages/5-key-terms |
amphiphilic : molecule possessing a polar or charged area and a nonpolar or uncharged area capable of interacting with both hydrophilic and hydrophobic environments | https://openstax.org/books/biology/pages/5-key-terms |
antiporter : transporter that carries two ions or small molecules in different directions | https://openstax.org/books/biology/pages/5-key-terms |
aquaporin : channel protein that allows water through the membrane at a very high rate | https://openstax.org/books/biology/pages/5-key-terms |
carrier protein : membrane protein that moves a substance across the plasma membrane by changing its own shape | https://openstax.org/books/biology/pages/5-key-terms |
caveolin : protein that coats the cytoplasmic side of the plasma membrane and participates in the process of liquid update by potocytosis | https://openstax.org/books/biology/pages/5-key-terms |
channel protein : membrane protein that allows a substance to pass through its hollow core across the plasma membrane | https://openstax.org/books/biology/pages/5-key-terms |
clathrin : protein that coats the inward-facing surface of the plasma membrane and assists in the formation of specialized structures, like coated pits, for phagocytosis | https://openstax.org/books/biology/pages/5-key-terms |
concentration gradient : area of high concentration adjacent to an area of low concentration | https://openstax.org/books/biology/pages/5-key-terms |
diffusion : passive process of transport of low-molecular weight material according to its concentration gradient | https://openstax.org/books/biology/pages/5-key-terms |
electrochemical gradient : gradient produced by the combined forces of an electrical gradient and a chemical gradient | https://openstax.org/books/biology/pages/5-key-terms |
electrogenic pump : pump that creates a charge imbalance | https://openstax.org/books/biology/pages/5-key-terms |
endocytosis : type of active transport that moves substances, including fluids and particles, into a cell | https://openstax.org/books/biology/pages/5-key-terms |
exocytosis : process of passing bulk material out of a cell | https://openstax.org/books/biology/pages/5-key-terms |
facilitated transport : process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins | https://openstax.org/books/biology/pages/5-key-terms |
fluid mosaic model : describes the structure of the plasma membrane as a mosaic of components including phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains attached to proteins or lipids, respectively), resulting in a fluid character (fluidity) | https://openstax.org/books/biology/pages/5-key-terms |
glycolipid : combination of carbohydrates and lipids | https://openstax.org/books/biology/pages/5-key-terms |
glycoprotein : combination of carbohydrates and proteins | https://openstax.org/books/biology/pages/5-key-terms |
hydrophilic : molecule with the ability to bond with water; âwater-lovingâ | https://openstax.org/books/biology/pages/5-key-terms |
hydrophobic : molecule that does not have the ability to bond with water; âwater-hatingâ | https://openstax.org/books/biology/pages/5-key-terms |
hypertonic : situation in which extracellular fluid has a higher osmolarity than the fluid inside the cell, resulting in water moving out of the cell | https://openstax.org/books/biology/pages/5-key-terms |
hypotonic : situation in which extracellular fluid has a lower osmolarity than the fluid inside the cell, resulting in water moving into the cell | https://openstax.org/books/biology/pages/5-key-terms |
integral protein : protein integrated into the membrane structure that interacts extensively with the hydrocarbon chains of membrane lipids and often spans the membrane; these proteins can be removed only by the disruption of the membrane by detergents | https://openstax.org/books/biology/pages/5-key-terms |
isotonic : situation in which the extracellular fluid has the same osmolarity as the fluid inside the cell, resulting in no net movement of water into or out of the cell | https://openstax.org/books/biology/pages/5-key-terms |
osmolarity : total amount of substances dissolved in a specific amount of solution | https://openstax.org/books/biology/pages/5-key-terms |
osmosis : transport of water through a semipermeable membrane according to the concentration gradient of water across the membrane that results from the presence of solute that cannot pass through the membrane | https://openstax.org/books/biology/pages/5-key-terms |
passive transport : method of transporting material through a membrane that does not require energy | https://openstax.org/books/biology/pages/5-key-terms |
peripheral protein : protein found at the surface of a plasma membrane either on its exterior or interior side; these proteins can be removed (washed off of the membrane) by a high-salt wash | https://openstax.org/books/biology/pages/5-key-terms |
pinocytosis : a variation of endocytosis that imports macromolecules that the cell needs from the extracellular fluid | https://openstax.org/books/biology/pages/5-key-terms |
plasmolysis : detaching of the cell membrane from the cell wall and constriction of the cell membrane when a plant cell is in a hypertonic solution | https://openstax.org/books/biology/pages/5-key-terms |
potocytosis : variation of pinocytosis that uses a different coating protein (caveolin) on the cytoplasmic side of the plasma membrane | https://openstax.org/books/biology/pages/5-key-terms |
primary active transport : active transport that moves ions or small molecules across a membrane and may create a difference in charge across that membrane | https://openstax.org/books/biology/pages/5-key-terms |
pump : active transport mechanism that works against electrochemical gradients | https://openstax.org/books/biology/pages/5-key-terms |
receptor-mediated endocytosis : variation of endocytosis that involves the use of specific binding proteins in the plasma membrane for specific molecules or particles, and clathrin-coated pits that become clathrin-coated vesicles | https://openstax.org/books/biology/pages/5-key-terms |
secondary active transport : movement of material that is due to the electrochemical gradient established by primary active transport | https://openstax.org/books/biology/pages/5-key-terms |
selectively permeable : characteristic of a membrane that allows some substances through but not others | https://openstax.org/books/biology/pages/5-key-terms |
solute : substance dissolved in a liquid to form a solution | https://openstax.org/books/biology/pages/5-key-terms |
symporter : transporter that carries two different ions or small molecules, both in the same direction | https://openstax.org/books/biology/pages/5-key-terms |
tonicity : amount of solute in a solution | https://openstax.org/books/biology/pages/5-key-terms |
transport protein : membrane protein that facilitates passage of a substance across a membrane by binding it | https://openstax.org/books/biology/pages/5-key-terms |
transporter : specific carrier proteins or pumps that facilitate movement | https://openstax.org/books/biology/pages/5-key-terms |
uniporter : transporter that carries one specific ion or molecule | https://openstax.org/books/biology/pages/5-key-terms |
Cells perform the functions of life through various chemical reactions. A cellâs metabolism refers to the chemical reactions that take place within it. There are metabolic reactions that involve the breaking down of complex chemicals into simpler ones, such as the breakdown of large macromolecules. This process is re... | https://openstax.org/books/biology/pages/6-chapter-summary |
Energy comes in many different forms. Objects in motion do physical work, and kinetic energy is the energy of objects in motion. Objects that are not in motion may have the potential to do work, and thus, have potential energy. Molecules also have potential energy because the breaking of molecular bonds has the potenti... | https://openstax.org/books/biology/pages/6-chapter-summary |
The âG of a reaction can be negative or positive, meaning that the reaction releases energy or consumes energy, respectively. A reaction with a negative âG that gives off energy is called an exergonic reaction. One with a positive âG that requires energy input is called an endergonic reaction. Exergonic reacti... | https://openstax.org/books/biology/pages/6-chapter-summary |
In studying energy, scientists use the term âsystemâ to refer to the matter and its environment involved in energy transfers. Everything outside of the system is called the surroundings. Single cells are biological systems. Systems can be thought of as having a certain amount of order. It takes energy to make a sys... | https://openstax.org/books/biology/pages/6-chapter-summary |
A series of laws, called the laws of thermodynamics, describe the properties and processes of energy transfer. The first law states that the total amount of energy in the universe is constant. This means that energy canât be created or destroyed, only transferred or transformed. The second law of thermodynamics state... | https://openstax.org/books/biology/pages/6-chapter-summary |
ATP is the primary energy-supplying molecule for living cells. ATP is made up of a nucleotide, a five-carbon sugar, and three phosphate groups. The bonds that connect the phosphates (phosphoanhydride bonds) have high-energy content. The energy released from the hydrolysis of ATP into ADP + Piis used to perform cellular... | https://openstax.org/books/biology/pages/6-chapter-summary |
Enzymes are chemical catalysts that accelerate chemical reactions at physiological temperatures by lowering their activation energy. Enzymes are usually proteins consisting of one or more polypeptide chains. Enzymes have an active site that provides a unique chemical environment, made up of certain amino acid R groups ... | https://openstax.org/books/biology/pages/6-chapter-summary |
Enzyme action must be regulated so that in a given cell at a given time, the desired reactions are being catalyzed and the undesired reactions are not. Enzymes are regulated by cellular conditions, such as temperature and pH. They are also regulated through their location within a cell, sometimes being compartmentalize... | https://openstax.org/books/biology/pages/6-chapter-summary |
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