What is the main characteristic of passive transport?

The main characteristic of passive transport is that substances move without the use of energy. This process occurs along a concentration gradient, meaning that molecules move from areas of higher concentration to areas of lower concentration until equilibrium is reached.

Passive transport includes various mechanisms such as simple diffusion, facilitated diffusion, and osmosis, all of which do not require ATP or other forms of energy. This characteristic distinguishes passive transport from active transport, where energy is needed to move substances against their concentration gradients. Understanding the nature of passive transport is fundamental in pharmacology, especially when considering how drugs and other substances enter or leave cells.