Movement across membranes

diffusion

high to low concentration

concentration gradient

difference in number of molecules from one place to the next

dialysis

diffusion of small solutes through a selectively permeable membrane.

facilitated diffusion

diffusion of molecules across cell membranes through protein channels

active transport

the movement of ions or molecules across a cell membrane into a region of higher concentration, requiring energy

Exocytosis

release of substances out a cell by the fusion of a vesicle with the membrane

Endocytosis

A process in which a cell engulfs extracellular material through an inward folding of its plasma membrane.

Phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells

Pinocytosis

process by which a cell takes in liquid from the surrounding environment

receptor-mediated endocytosis

the uptake into a cell of many specific molecules at once using a cell's receptor proteins

isotonic solution

a solution whose solute concentration is equal to the solute concentration inside a cell

hypotonic solution

A solution in which the concentration of solutes is less than that of the cell that resides in the solution, causing a cell to swell (or lyse)

hypertonic solution

A solution in which the concentration of solutes is greater than that of the cell that resides in the solution, causing a cell to shrink (crenate)

Osmosis

diffusion of water across a selectively permeable membrane

protein pump

type of cell membrane protein used to move small things (usually ions) against the concentration gradient (against diffusion)