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Chapter 5
Biology
| Term | Definition |
|---|---|
| passive transport | the movement of substances across the 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 the 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 in the inside of cell walls and that is caused by the movement of water into the cells |
| plasmolysis | the concentration or shrinking of the cell membrane of a plant cell in a hypertonic solution in response to the loss of water by osmosis |
| cytolysis | the soluble portion of the cytoplasm, which includes molecules and small particles, such as ribosomes, but not the organelles covered with membranes |
| 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 protein molecules in a cell membrane that form 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 in to 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 |
| vesicle | a small cavity or sac that contains materials in a eukaryotic cells; forms when part of the cell membrane surrounds the materials to be taken into the cell or transported within the cell |
| pinocytosis | a method of active transport across the cell membrane in which the cell takes in extracellular fluids |
| 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 (digest) foreign matter or microorganisms |
| exocytosis | the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out |
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