Additional Science - Biology - Unit 2 - Diffusion

Dissolved substances have to pass through the cell membrane to get into or out of a cell.

Diffusion is one of the processes that allows this to happen.

Diffusion occurs when particles spread.

They move from a region where they are in high concentration to a region where they are in low concentration.

Diffusion happens when the particles are free to move.

This is true in gases and for particles dissolved in solutions.

Particles diffuse down a concentration gradient, from an area of high concentration to an area of low concentration.

In the gut, digested food products move from the gut cavity to the blood in the capillary of villus. This moves all of the important nutrients and minerals from the food you eat into the cells lining the intestine and into the bloodstream.

In the lungs, oxygen particles move from the alveolar air space to the  blood circulation around the lungs. Oxygen diffuses across the alveolar walls into the blood, and the circulation takes the oxygen-rich blood away.

Particles will continue to move from a high to a low concentration while the concentration is different between two areas.