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BIOL 114
Ch 5: The Working Cell
| Term | Definition |
|---|---|
| activation energy | The amount of energy that reactants must absorb before a chemical reaction will start. |
| active site | The part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme's surface. |
| active transport | The movement of a substance across a biological membrane against its concentration gradient, aided by specific transport proteins and requiring input of energy (often as ATP). |
| ADP | A molecule composed of adenosine and two phosphate groups. The molecule ATP is made by combining a molecule of ADP with a third phosphate in an energy-consuming reaction. |
| ATP | A molecule composed of adenosine and three phosphate groups; the main energy source for cells. |
| calorie | The amount of energy that raises the temperature of 1 g of water by 1°C. |
| chemical energy | Energy stored in the chemical bonds of molecules; a form of potential energy. |
| concentration gradient | An increase or decrease in the density of a chemical substance within a given region. Cells often maintain concentration gradients of hydrogen ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated. |
| conservation of energy | The principle that energy can neither be created nor destroyed. |
| diffusion | The spontaneous movement of particles of any kind down a concentration gradient; that is, movement of particles from where they are more concentrated to where they are less concentrated. |
| endocytosis | The movement of materials into the cytoplasm of a cell via vesicles or vacuoles. |
| Energy | The capacity to perform work, or to move matter in a direction it would not move if left alone. |
| Entropy | A measure of disorder, or randomness. One form of disorder is heat, which is random molecular motion. |
| enzyme inhibitors | A chemical that interferes with an enzyme's activity by changing the enzyme's shape, either by plugging up the active site or binding to another site on the enzyme. |
| enzymes | A protein that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed in the process. |
| exocytosis | The movement of materials out of the cytoplasm of a cell via membranous vesicles or vacuoles. |
| facilitated diffusion | The passage of a substance across a biological membrane down its concentration gradient, aided by specific transport proteins. |
| feedback regulation | A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway. |
| hypertonic | In comparing two solutions, referring to the one with the greater concentration of solutes. |
| hypotonic | In comparing two solutions, referring to the one with the lower concentration of solutes. |
| induced fit | The interaction between a substrate molecule and the active site of an enzyme, which changes shape slightly to embrace the substrate and catalyze the reaction. |
| isotonic | Having the same solute concentration as another solution. |
| kinetic energy | Energy of motion. Moving matter performs work by transferring its motion to other matter, such as leg muscles pushing bicycle pedals. |
| metabolism | The total of all the chemical reactions in an organism. |
| osmoregulation | The control of the gain or loss of water and dissolved solutes in an organism. |
| osmosis | The diffusion of water across a selectively permeable membrane. |
| passive transport | The diffusion of a substance across a biological membrane without any input of energy. |
| phagocytosis | Cellular "eating"; a type of endocytosis whereby a cell engulfs large molecules, other cells, or particles into its cytoplasm. |
| pinocytosis | Cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles. |
| plasmolysis | A phenomenon that occurs in plant cells in a hypertonic environment. The cell loses water and shrivels, and its plasma membrane pulls away from the cell wall, usually killing the cell. |
| Potential energy | Stored energy; the energy that an object has due to its location and/or arrangement. Water behind a dam and chemical bonds both possess potential energy. |
| receptor-mediated endocytosis | The movement of specific molecules into a cell by the inward budding of vesicles. The vesicles contain proteins with receptor sites specific to the molecules being taken in. |
| signal transduction pathway | A series of molecular changes that converts a signal on a target cell's surface to a specific response inside the cell. |
| substrate | (1) A specific substance (reactant) on which an enzyme acts. Each enzyme recognizes only the specific substrate of the reaction it catalyzes. (2) A surface in or on which an organism lives. |
| transport protein | A membrane protein that helps move substances across a cell membrane. |
Created by:
EdL
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