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| A property of biological membranes that allows some substances to cross more easily than others |
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| A molecule that has both a hydrophilic region and a hydrophobic region |
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| The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individual protein molecules drifting laterally in a fluid bilayer of phospholipids |
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| Typically a trans membrane protein with hydrophobic regions that completely spans the hydrophobic interior of the membrane |
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| A protein appendage loosely bound to the surface of a membrane and not embeedded in the lipid bilayer |
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| A lipid covalently attached to a carbohydrate |
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| A protein covalently attached to a carbohydrate |
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| A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane |
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| A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis) |
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| The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area |
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| An increase or decreased in the density of a chemical substance in an area. Cells often maintain concentration gradients of 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 |
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| The diffusion of a substance across a biological membrane |
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| The diffusion of water across a selectively permeable membrane |
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| The ability of a solution to cause a cell within it to gain or lose water |
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| Having the same solute concentration as another solution |
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| In comparing two solutions, referring to the one with a greater solute concentration |
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| In comparing two solutions, referring to the one with a lower solute concentration |
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| How organisms regulate solute concentrations and balance the gain and loss of water |
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| Very firm. A walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in entry of water |
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| Limp. A waled cell is flaccid in surrounds where there is no tendency for water to enter |
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| The spontaneous pass of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients |
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| Opens or closes in response to a particular stimulus |
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| Protein channel in a cell membrane that allows passage of a specific ion d own its concentration gradient |
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| the movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins |
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| A special transport protein in the plasma membrane of animal cells that transports sodium out of the cell and potassium into the cell against their concentration gradients |
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| The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances |
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| The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential |
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| An ion transport protein that generates voltage across a membrane |
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| An active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process |
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| The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient |
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| A molecule that binds specifically to a receptor site of another molecule |
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| The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane |
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| the cell taking in macromolecules and forming new vesicles from the plasma membrane |
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| a cell engulfs a particle by wraping pseudopedia around it and packaging it within a membrane-enclosed sac large enough to be classified as a vacuole |
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| the cell "gulps" droplets of extracelular fluid into tiny vesicles |
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