Morris, Biology for the AP Course 1e - Mod 10

concentration gradient

A difference in concentration of a substance, with regions of higher and lower concentration.

passive transport

The movement of molecules across a cell membrane by diffusion.

facilitated diffusion

Diffusion across a cell membrane through a transmembrane protein, such as a channel or carrier.

channel protein

A transport protein with a passage that allows the movement of molecules through it.

carrier protein

A transport protein that facilitates movement of molecules across a cell membrane.

aquaporin

A channel protein that allows water to cross the cell membrane more readily than by diffusing through the lipid bilayer.

active transport

The movement of substances across a cell membrane against a concentration gradient requiring an input of energy.

primary active transport

Active transport that uses the energy of ATP directly.

secondary active transport

Active transport that uses the energy of an electrochemical gradient to drive the movement of molecules.

exocytosis

The process in which a vesicle fuses with the cell membrane and empties its contents into the extracellular space or delivers proteins to the cell membrane.

endocytosis

The process in which a vesicle buds off from the cell membrane, bringing material from outside the cell into that vesicle, which can then fuse with other membranes.