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Chater 5
Vocabulary
| Term | Definition |
|---|---|
| passive transport | the movement of substances across a cell membrane without the use of energy by the cell. |
| diffusion | the movement of particles from regions of higher density to regions of lower density |
| concentration gradient | a difference in the concentration of a substance across a distance |
| equilibrium | a state that exists when the concentration of a substance is the same throughout a space |
| osmosis | the diffusion of water or another solvent from a more dilute solution to a more concentrated solution through a membrane that is permeable to the solvent. |
| hypotonic | describes a solution whose solute concentration is lower than the solute concentration inside a cell. |
| hypertonic | describes a solution whose solute concentration is higher than the solute concentration inside a cell. |
| isotonic | describes a solution whose solute concentration is equal to the solute concentration inside a cell. |
| contractile vacuole | in protists, an organelle that accumulates water and then releases it periodically to maintain osmotic pressure. |
| turgor pressure | the pressure that is exerted on the inside of cell walls and that is caused by the movement of water into the cell. |
| plasmolysis | the contraction or shrinking of the cell membrane of a plant cell in a hypertonic solution I response to the loss of water by osmosis. |
| cytolysis | the bursting of a cell |
| facilitated diffusion | the transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins. |
| carrier protein | a protein that transports substances across a cell membrane. |
| ion channel | a complex of proteins molecules in a cell membrane that forms a pore through which ions can pass. |
| active transport | the movement of chemical substances, usually across the cell membrane, against a concentration gradient; requires cells to use energy. |
| sodium-potassium pump | a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell. |
| endocytosis | the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell. |
| phagocytosis | the process by which a cell engulfs large particles or whole cells, either as a defense mechanism or as a means to obtain food. |
| phagocyte | a cell that ingests and destroys foreign matter or microorganisms. |
| exocytosis | the process by which a substance is released from the cell through a vesicle that transports the substances to the cell surface and then fuses with the membrane to let the substance out. |