Consider the hypothetical experiment described below and apply your knowledge of
ID: 43802 • Letter: C
Question
Consider the hypothetical experiment described below and apply your knowledge of inhibitors of electron transport and oxidative phosphorylation. There may be more than one right answer, but there are definitely some that are not right. You have coupled, functioning mitochondria and provide NADH and 02. If only ATP synthase is inhibited (this is not an uncoupler, instead proton movement through ATP synthase is prevented) would the spectral data of the cytochromes in intact mitochondria indicate that they were ail reduced, all oxidized or somewhere in between? Explain your rationale. Would the system be any different if an artificial electron acceptor was used at Complex III? Explain.Explanation / Answer
a. ATP synthase is an enzyme which is responsible to transport protons across the inner mitochondrial membrane. This creates an electrochemical gradient for electron transport chain which reduces a series of cytochromes to generate ATP molecules. When an electrochemical gradient generation is prevented by use of ATP synthase proton pump inhibitors reduction of cytochromes to generate ATP is also affected. Hence the spectral data will indicate that the cytochromes in the intact inner mitochondrial membrane will be in oxidized state.
b. The system will not be different even if an artificial electron acceptor was used at Complex III because due to inhibition of electrochemical gradient generation reduction of electron generating Complex I and Complex II is prevented. This restricts the source of generation and availability of electrons to be accepted by an artificial electron acceptor was used at Complex III.