Mitochondrial disease. A mutation in a mitochondrial gene encoding a component of ATP synthase has been identified. People who have this mutation suffer from muscle weakness, ataxia (uncoordinated movement), and retinitis pigmentosa. A tissue biopsy was performed on each of three patients having this mutation, and submitochondrial particles were isolated that were capable of succinate-sustained ATP synthesis. First, the activity of the ATP synthase was measured on the addition of succinate and the below results were obtained. (a) What was the purpose of the addition of succinate? (b) What is the effect of the mutation on succinate-coupled ATP synthesis? Next, the ATPase activity of the enzyme was measured by incubating the submitochondrial particles with ATP in the absence of succinate. (c) Why was succinate omitted from the reaction? (d) What is the effect of the mutation on ATP hydrolysis? (e) What do these results, in conjunction with those obtained in the first experiment, tell you about the nature of the mutation?