Diffusion

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration, driven by random molecular motion. This process occurs because particles naturally disperse to achieve uniform distribution in their environment.

Passive nature of diffusion means the process requires no input of cellular energy, relying entirely on the kinetic energy of particles. As temperature increases, particle kinetic energy rises, leading to faster diffusion rates.

Concentration gradients represent differences in particle concentration between two regions, and diffusion continues until equilibrium is reached. Even at equilibrium, particles continue random motion, but there is no net movement.

Kinetic theory foundation explains that particles are always in random motion, and diffusion emerges from the statistical tendency for particles to move from crowded regions to less crowded ones. This principle applies to gases and liquids because their particles can move freely.

Membrane permeability determines whether diffusion can occur across a boundary, as only particles small enough or non‑polar enough can pass through directly. Biological membranes are partially permeable, meaning only specific substances diffuse freely.

Identifying direction of diffusion requires comparing concentrations inside and outside a region or cell to determine where particles will move. This step is essential in biological contexts where concentration gradients change with conditions.

Assessing rate of diffusion involves analyzing factors such as temperature, surface area, and diffusion distance. Each factor influences how quickly equilibrium is reached, allowing prediction of how efficiently substances enter or leave cells.