| A | B |
|---|
| active transport | movement across a membrane against its concentration or electrochemical gradient using energy input and transport proteins |
| amphipathic molecule | molecule that has both a hydrophilic region and a hydrophobic region |
| aquaporin | transport protein facilitates diffusion of water across the membrane |
| concentration gradient | increase or decrease in the density of a chemical substance in an area |
| cotransport | coupling of the downhilldiffusion of one substance to the uphilltransport of another |
| diffusion | ubstance movement down its concentration gradient from more concentrated to less concentrated area |
| electrochemical gradient | diffusion gradient of an ion |
| electrogenic pump | ion transport protein that generates voltage across a membrane |
| endocytosis | plasma membrane surrounds substance and pinch off to form an intracellular vesicle |
| exocytosis | cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane |
| facilitated diffusion | passage of molecules and ions |
| flaccid | limp |
| fluid mosaic model | membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids |
| gated channel | protein channel in a cell membrane that opens or closes in response to a particular stimulus |
| glycolipid | lipid covalently attached to a carbohydrate |
| glycoprotein | protein covalently attached to a carbohydrate |
| hypertonic | comparing two solutions |
| hypotonic | comparing two solutions |
| integral protein | transmembrane protein with hydrophobic regions that span the interior of the membrane |
| ion channel | Protein channel in a cell membrane that allows passage of a specific ion |
| isotonic | Having the same solute concentration as another solution |
| ligand | molecule that binds specifically to a receptor site of another molecule |
| membrane potential | charge difference between a cell’s cytoplasm and the extracellular fluid |
| osmoregulation | regulation of solute and water concentrations in body fluids by organisms |
| osmosis | diffusion of water across a selectively permeable membrane |
| passive transport | diffusion of a substance across a biological membrane without energy use |
| peripheral protein | protein appendage loosely bound to the surface of a membrane and not embedded in the lipid bilayer |
| phagocytosis | endocytosis involving large |
| pinocytosis | endocytosis in which the cell ingests extracellular fluid and its dissolved solutes |
| plasmolysis | cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment |
| proton pump | active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell |
| receptor-mediated endocytosis | movement into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific for molecules |
| selective permeability | allows some substances to cross more easily than others |
| sodium-potassium pump | protein that transports sodium out of the cell and potassium into the cell against their concentration gradients |
| tonicity | ability of a solution to cause a cell within it to gain or lose water |
| transport protein | protein that helps a certain substance or class of closely related substances to cross the membrane |
| turgid | very firm cell are turgid with greater solute concentration than surroundings |
