Question

Why do materials diffuse across a membrane?

Answer 1

By diffusion the molecules move from an area of high concentration to an area of low concentration and also by active process.

Explanation:

1. Water, carbon dioxide, oxygen, ions etc., cross the cell membrane by a type diffusion 'osmosis'.
2. Diffusion is a principle method of movement of substances across the cell membrane.
3. By diffusion, the molecules passively move from an area of high concentration to an area of low concentration and also by active process, the molecules move against the concentration gradient.