| Term | Definition |
|---|
| characteristics of cell membrane? | it's a selectively permeable barrier that restricts free exchange between the cell and the interstitial fluid |
| what does movement of a substance across the membrane depend on? | the permeability of the membrane to that substance |
| how is movement of molecules across membranes classified? | either by energy requirements of by the physical means the molecule uses to cross the membrane |
| what diffuses through the phospholipid bilayer? | lipid-soluble substances |
| what do less lipid-soluble molecules require to cross the membrane? | the assistance of a membrane protein |
| what kind of transport does not require the input of energy? | passive transport |
| what is diffusion? | the passive movement of molecules down a chemical (concentration) gradient from an area of higher concentration to an area of lower concentration |
| when does net movement stop? | when the system reaches equilibrium |
| what continues when equilibrium is reached? | molecular movement |
| what does the diffusion rate depend on? | the magnitude of the concentration gradient |
| what is simple diffusion? | passive movement of molecules from high concentration to area of low concentration across a membrane and is directly proportional to membrane surface area, concentration gradient, and membrane permeability, and inversely proportional to membrane thickness |
| what are the seven properties of diffusion? | 1. passive process; 2. high concentration to low concentration; 3. net movement until concentration is equal; 4. rapid over short distances, slow over long distances; 5. directly related to temperature; 6. inversely related to molecular size; 7. in open system or across a partition |
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