What is the primary characteristic of passive transport?

The primary characteristic of passive transport is that it involves movement without energy input. This means that substances move across cell membranes freely, driven by concentration gradients – the difference in concentration of a substance inside and outside the cell. Because passive transport occurs in the direction of these gradients, it does not require cellular energy (like ATP) to facilitate the movement.

In passive transport, molecules tend to move from areas of higher concentration to areas of lower concentration until equilibrium is reached. This includes different forms such as simple diffusion, facilitated diffusion, and osmosis. Each of these processes relies on the natural kinetic energy of molecules rather than external energy sources.

Understanding passive transport is crucial for comprehending how cells maintain homeostasis, allowing necessary substances to enter or exit the cell without expending energy, thereby efficiently regulating internal conditions.