British Sign Language Glossaries of Curriculum Terms

BSL Environmental Science Glossary - Concentration gradient definition

Definition: The concentration gradient is the flow of a liquid or gas across a membrane from one side to the other so that the numbers reach the same on both sides - reaching an equilibrium. A membrane acts like a fence with holes, it will have a high concentration of a substance on one side and a lower concentration on the other.

A membrane with large holes will allow both large and small molecules through to the other side so that the other side increases in concentration of the substance until there is an equal amount on both sides. If a membrane has only small holes, it will only allow the smaller molecules through, not the larger ones. The large ones will be unable to fit through the small holes. So the large molecules will remain on one side, and the smaller molecules will equalise on both sides.