Cells and movement across membranes – WJECConcentration gradients

The idea of concentrations and the gradients within them is important when understanding the movement of particles or molecules across cell membranes.

Concentration

When sucrose is dissolved in water, the solute is sucrose and water is the solvent. Together they form a solution.

The more sucrose particles there are in a certain volume of the solution, the more concentrated the solution is.

A solution with a low solute concentration has a high water concentration. Pure water has the highest water concentration.

A concentration gradient exists when there is a region of high concentration leading to a region of low concentration:

• going from high to low concentration is going down the concentration gradient
• going from low to high concentration is going against the concentration gradient