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Adv. Bio Chapter 7
Membranes
Term | Definition |
---|---|
Selective Permeability | A property of biological membranes that allows them to regulate the passage of substances across them. |
Fluid Mosaic Model | The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids. |
Glycoprotein | A protein with one or more covalently attached carbohydrates. |
Osmosis | The diffusion of free water across a selectively permeable membrane. |
Tonicity | The ability of a solution surrounding a cell to cause that cell to gain or lose water. |
Isotonic | Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell. |
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. |
Facilitated Diffusion | The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure. |
Active Transport | The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy. |
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. |
Exocytosis | The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane. |
Ligand | A molecule that binds specifically to another molecule, usually a larger one. |
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). |