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Q4 - Uncouplers and Inhibitors of Oxidative Phosphorylation

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Bioenergetics & Central Metabolism Overview

When isolated mitochondria are suspended in a buffer containing ADP, Pi, and an oxidizable substrate, three easily measured processes occur: the substrate is oxidized; O2 is consumed; and ATP is synthesized. Cyanide (CN-) is an inhibitor of the passage of electrons to O2. Oligomycin inhibits ATP synthase by interacting with subunit F0. 2,4-dinitrophenol (DNP) can diffuse readily across mitochondrial membranes and release a proton into the matrix, thus dissipating the proton gradient.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. x is the oxidizable substrate.
B. y is either oligomycin or CN-.
C. z is DNP.
D. If z is a mixture of oligomycin and DNP, the ATP synthesis will not level off.
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Question reproduced from IBO 2016, Theoretical Paper A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)