AP Bio Study Guide

Big Idea 2.B

What is passive transport?

Passive transport is the movement of molecules down a concentration gradient from a region of high concentration to a region of low concentration until equilibrium is reached. It does not require the input of metabolic energy (such as ATP). Examples include diffusion and osmosis. Diffusion is the random movement of molecules or other particles from a higher concentration to a lower concentration, while osmosis is the term used specifically for diffusion of water.