Movement in and out of the cells

Diffusion is the movement of a substance from a region of higher concentration to a region of lower concentration

Role of diffusion in living organisms ?

•Diffusion is important to organisms because it is the process by which useful molecules enter the body cells and waste products are removed.

The intestines

Digested food molecules (amino acids, glucose) move down a concentration gradient from the intestine to the blood. Waste products such as carbon dioxide or urea travel by diffusion from body cells into the bloodstream.

The lungs

Oxygen moves from high concentration (in the air sac) to a lower concentration (in the blood). Carbon dioxide moves from high concentration (in the blood) to a lower concentration (in the air sac).

What are the factors affecting diffusion?

•Extent of the concentration gradient: The greater the difference in concentration, the more rapid the diffusion.
•Mass of the molecules diffusing: Heavier molecules move more slowly; therefore, they diffuse more slowly. The reverse is true for lighter molecules.
•Temperature: Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion.

Surface area and thickness of the plasma membrane: Increased surface area increases the rate of diffusion, whereas a thicker membrane reduces it.

Distance travelled: The greater the distance that a substance must travel, the slower the rate of diffusion

Posted in: Biology