CK-12 Biology - Chapter 3

active transport

Active transport occurs when energy is needed for a substance to move across a plasma membrane.

endocytosis

Endocytosis is the type of vesicle transport that moves a substance into the cell. The plasma membrane completely engulfs the substance, a vesicle pinches off from the membrane, and the vesicle carries the substance into the cell.

exocytosis

Exocytosis is the type of vesicle transport that moves a substance out of the cell. A vesicle containing the substance moves through the cytoplasm to the cell membrane.

diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

osmosis

Osmosis is a special type of diffusion — the diffusion of water molecules across a membrane.

passive transport

Passive transport occurs when substances cross the plasma membrane without any input of energy from the cell