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Chapter 7 Key Terms
Chapter 7: Membrane Structure and Function
| Term | Definition |
|---|---|
| aquaporins | A channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of free water across the membrane. |
| concentration gradient | A region along which the density of a chemical substance increases or decreases. |
| cotransport | The coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient. |
| diffusion | The spontaneous movement of a substance down its concentration or electrochemical gradient, from a region where it is more concentrated to a region where it is less concentrated. |
| electrochemical gradient | The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force). |
| electrogenic pump | An active transport protein that generates voltage across a membrane while pumping ions. |
| endocytosis | Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane. |
| exocytosis | The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane. |
| flaccid | Limp. Lacking turgor, as in a plant cell in surroundings where there is a tendency for water to leave the cell. (A walled cell becomes flaccid if it has a higher water potential than its surroundings, resulting in the loss of water.) |
| glycoprotein | A protein with one or more covalently attached carbohydrates. |
| hypertonic | Referring to a solution that, when surrounding a cell, will cause the cell to lose water. |
| hypotonic | Referring to a solution that, when surrounding a cell, will cause the cell to take up water. |
| ion channel | A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient. |
| membrane potential | The difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances. |
| osmoregulation | Regulation of solute concentrations and water balance by a cell or organism. |
| plasmolysis | A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment. |
| selective permeability | A property of biological membranes that allows them to regulate the passage of substances across them. |
| sodium-potassium pump | A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell. |
| turgid | Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a lower water potential than its surroundings, resulting in entry of water.) |
Created by:
taylor.wendell
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