What is the key difference between passive and active transport?

The key difference between passive and active transport lies in the energy requirements and the mechanisms of movement across cell membranes. Active transport requires energy, typically in the form of ATP, to move substances against their concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This process is crucial for maintaining concentration gradients of ions and molecules that are necessary for various cellular functions, such as nutrient uptake, ion balance, and waste removal.

In contrast, passive transport does not require energy as it relies on the natural tendency of molecules to move from areas of higher concentration to areas of lower concentration until equilibrium is reached. This movement occurs through processes such as diffusion, facilitated diffusion, and osmosis.

Understanding these concepts is essential for grasping how cells maintain homeostasis and manage their internal environments effectively.