The rate of diffusion for water-soluble substances through a membrane decreases as
A)their concentration gradient increases
B)their molecular weight increases
C)the number of cholesterol molecules in the membrane increases
D)the membrane's surface area increases
E)the number of membrane carbohydrates increases

Question

Quizplus · Accepted Answer

The rate of diffusion is inversely proportional to the molecular weight of the substance. The larger the molecular weight, the slower the rate of diffusion. Therefore, as the molecular weight of a substance increases, its rate of diffusion through a membrane decreases.

The Rate of Diffusion for Water-Soluble Substances Through a Membrane