What is the difference between passive and active transport?

Passive transport is characterized by the movement of molecules across the cell membrane without the expenditure of energy. This process occurs naturally, driven by the concentration gradient, where substances move from an area of higher concentration to an area of lower concentration until equilibrium is reached. Examples of passive transport include diffusion, facilitated diffusion, and osmosis.

Active transport, on the other hand, requires energy to move substances against their concentration gradient, from an area of lower concentration to an area of higher concentration. This is essential for maintaining concentration differences across membranes, which are critical for various cellular functions. Active transport often involves specific proteins, such as pumps, that enable this energy-dependent movement.

Understanding the distinction between these two types of transport is crucial in cellular biology, as it highlights how cells manage the import and export of various substances to maintain homeostasis and support their metabolic activities.