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| allows some substances to cross more easily than others |
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| a phospholipid that has both a hydrophilic region and a hydrophobic region |
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| model of cell membrane structure; which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids |
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| transmembrane proteins, with hydrophobic regions that completely span the hydrophobic interior of the membrane |
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| appendages loosely bound to the surface of the membrane |
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| spans the membrane; helps move specific molecules across the membrane |
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| tendency for molecules of any substance to spread out into the available space |
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| diffusion of substance across a biological membrane |
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| The relation of two given areas, where the concentration of a particular substance differs between those areas. Diffusion will result in this substance moving along a concentration gradient until the concentration of the two areas becomes equal. |
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| solution with a higher concentration of solutes |
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| solution with lower solute concentration |
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| solutions of equal solute concentration |
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| passive transport; diffusion of water across a selectively permeable membrane |
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| spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradient |
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| plasma membrane pulling away from the wall as the plant cell shrivels |
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| a stimulus that cause transport proteins to open or close |
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| pumping a molecule across a membrane against its gradient; using it's own metabolic energy |
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| exchanges sodium for potassium across the plasma membrane of animal cells |
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| voltage across a membrane |
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| combination of forces acting on an ion |
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| transport protein that generates voltage across a membrane |
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| main electrogenic pump of plants, bacteria and fungi; actively transports hydrogen ions (protons) out of the cell |
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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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| secretes macromolecules by the fusion of vesicles with the plasma membrane |
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| cell takes in macromolecules and particulate matter by forming new vesicles from the plasma membrane |
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| a cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane enclosed sac |
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| cell gulps droplets of extracellular fluid in tiny vesicles |
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| receptor-mediated endocytosis |
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| movement of specific molecules into a cell by the inward budding of membranous besicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances |
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| extracellular substances that bind to the receptors |
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