Question

You are asked to study a new inhibitor of oxidative phosphorylation. When it is added to a suspension of mitochondria carrying out this process, both ATP synthesis and oxygen consumption are inhibited. You suspect that the inhibitor blocks either the F-type ATPase or the electron transport chain. You can perform an experiment that measures the consumption of oxygen and the synthesis of ATP by isolated mitochondria. In one paragraph (6 sentences maximum), explain how the uncoupler, dinitrophenol, can be used to determine whether the inhibitor blocks the ATPase or the electron transport chain.

This was all the information that was given.

Answer 1

DNP produces the loss of the proton gradient (i.e., the energy of the proton gradient is dissipated in the form of heat instead to produce ATP)

Explanation:

2,4-Dinitrophenol (DNP) acts to shuttle H+ ions across cellular membranes, bypassing the ATP synthase used by mitochondria to generate ATP during cellular respiration. Since DNP is able to bypass ATP synthase, this compound uncouples the phosphorylation of ADP by the ATP synthase from the process of oxidation (i.e., transport of electrons). For example, in muscle cells, DNP may be used to shuttle calcium ions (Ca +) from mitochondrial stores, and free intracellular Ca+ ions are evidenced to produce muscle contraction.