Once inside the tubule, substances are reabsorbed through active transport or diffusion. The method of absorption for each substance depends in part on the concentration of each substance in the tubule and in the blood. a) What types of substances could be reabsorbed by diffusion?

b) For which types of substances would energy and active transport be required?

c) What are some ways that reabsorption by diffusion and active transport could be limited in the kidneys?