Diffusion Definition

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

It is a passive process driven by the random motion of particles, requiring no external energy input.

Diffusion Across Membranes

Cellular processes often involve the movement of substances across biological membranes, like the plasma membrane.

Small, uncharged molecules, such as oxygen (represented as $\text{O}_2$), can cross these membranes via diffusion, following their specific concentration gradients.

Applying Diffusion to Oxygen Movement

Oxygen moves from an area where its concentration is higher to an area where it is lower.

A primary example is the movement of oxygen into cells through the plasma membrane, essential for cellular respiration.

While oxygen also diffuses across membranes within other cells like White Blood Cells (WBCs), the core principle illustrated is diffusion across a plasma membrane.

Summary of Process

The movement of oxygen across the plasma membrane is a direct and fundamental application of the diffusion process.