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Cells Unit
4. Exchange with the Environment
| Term | Definition |
|---|---|
| Cell Division | Allows organisms to grow and repair injuries. |
| Where does the exchange of materials between a cell and its environment take place? | At the cell membrane. |
| diffusion | the movement of particles from regions of higher density to regions of low density. |
| osmosis | the diffusion of water through a semipermeable membrane. The concentration of particles in blood is kept in check by osmosis. |
| molecules | particles that make up water |
| Semipermeable | only certain substances can pass through the membrane |
| channels | particles cross cell membranes by way of these |
| Passive Transport | the movement of substances across a cell membrane without the use of energy (diffusion and osmosis) |
| Active Transport | the movement of substances across a cell membrane that requires the cell to use energy |
| small particles move through membranes by | diffusion, passive transport and active transport |
| Large particles move through membranes by | endocytosis and exocytosis |
| endocytosis | the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring particle in the cell |
| vesicles | sacs formed from pieces of cell membrane. |
| exocytosis | the process in which a cell releases a particle by enclosing the particle in a vesicle that then moves to the cell surface and fuses with the cell membrane. |