| A | B |
|---|
| Passive transport | movement across the cell membrane that does not require energy |
| Concentration gradient | a difference in the concentration of a substance |
| Equilibrium | concentration of a substance is equal throughout |
| Osmosis | movement of water down a concentration gradient across a selectively permeable membrane |
| Diffusion | random movement of a substance from an area of high concentration to an area of low concentration |
| Ion channel | a transport protein with a polar pore through which ions can pass – a tunnel with gates |
| Facilitated diffusion | carries specific substances (esp. sugars and amino acids) across the membrane down the concentration gradient |
| Active transport | transport of substances across the cell membrane against the concentration gradient – requires energy |
| Exocytosis | – transport of a substance in a vesicle out of the cell |
| Endocytosis | transport of a substance in a vesicle into the cell |
