1.
active transport: the movement of chemical substances, usually across the cell membrane, against a concentration gradient; requires cells to use energy.
2.
carrier protein: a protein that transports substances across a cell membrane.
3.
concentration gradient: a difference in the concentration of a substance across a distance.
4.
contractile vacuole: in protists, an organelle that accumulates water and then releases it periodically to maintain osmotic pressure.
5.
cytolysis: the bursting of a cell.
6.
diffusion: the movement of particles from regions of higher density to regions of lower density.
7.
endocytosis: the process by which a cell membranes surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell.
8.
equilibrium: in biology, a state that exists when the concentration of a substance is the same throughout a space.
9.
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.
10.
facilitated diffusion: the transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins.
11.
hypertonic: describes a solution whose solute concentration is higher than the solute concentration inside a cell.
12.
hypotonic: describes a solution whose solute concentration is lower than the solute concentration inside a cell.
13.
ion channel: a complex of protein molecules in a cell membrane that form a pore through which ions can pass.
14.
isotonic: describes a solution whose concentration is equal to the solute concentration inside a cell.
15.
osmosis: the diffusion of water or another solvent from a more dilute solution (of a solute) to a more concentrated (of the solute) through a membrane that is permeable to the solvent.
16.
passive transport: the movement of substances across a cell membrane without the use of energy by the cell.
17.
phagocyte: a cell that ingests and destroys (digests) foreign matter or microorganisms.
18.
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.
19.
pinocytosis: a method of active transport across the cell membrane in which the cell takes in extracellular fluids.
20.
plasmolysis: the contraction or shrinking of the cell membrane of a plant cell in a hypertonic solution in response to the loss of water by osmosis.
21.
sodium-potassium pump: a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell.
22.
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.
23.
vesicle: a small cavity or sac that contains materials in a eukaryotic cell; forms when part of the cell membrane surrounds the materials to be taken into the cell or transported within the cell.
