What does diffusion primarily involve?

Diffusion primarily involves the movement of gas and other substances from areas of higher concentration to areas of lower concentration. This process occurs spontaneously and does not require energy input from the cell, which differentiates it from transport mechanisms like active transport that do consume energy. In biological systems, diffusion is crucial for various processes including gas exchange in the lungs, nutrient absorption in the intestines, and waste removal at the cellular level. The movement of substances occurs due to the inherent kinetic energy of the particles, leading them to spread out in a medium until equilibrium is achieved. This concept is foundational in understanding how substances travel across cell membranes and within the body, highlighting its significance in pathophysiology.