Concentration gradients

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

Concentration

When sucrose is dissolved in water:

The more particles there are in a certain volume, the more concentrated those particles are.

Beaker filled with solution one. Low solute concentration, high water concentration and high water potential. Visualised by a large number of blue dots and a smaller number of large orange dots.

Solution one

Low solute concentration

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

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