2,4-dinitrophenol (DNP) is a drug that can shuttle protons across biological mem

Question

2,4-dinitrophenol (DNP) is a drug that can shuttle protons across biological membranes and was sometimes used as a diet drug in the 1930s. What would happen to the P/O ratio in individuals who were treated with DNP?

a. The P/O ratio would decrease.

b. The P/O ratio would increase. (incorrect)

c. The P/O ratio would not be effected by DNP treatment.

The P/O ratio is the phosphate-to-oxygen ratio, which is the amount of ATP synthesized her O2 molecule reduced. I thought the answer would be b, increase, because more protons would be able to move across the membrane thus increasing the ratio but I am wrong.

Explanation / Answer

P:O ratios. The number of molecules of inorganic phosphate incorporated into organic form per atom of oxygen consumed, termed the P:O ratio, was frequently used as an index of oxidative phosphorylation.

DNP is an uncoupler causing dissipation of the pH gradient, thus the [H+] concentration gradient driven ATP synthesis will still be inhibited by DNP.

explanation and mechanism:

DNP is an "uncoupling" agent that disconnects the mitochondrial electron transport system from ATP production. DNP dissipates the electron-motive force generated by the electron transport chain of respiration in the mitochondria; consequently, the rate of ATP production is reduced. The free energy released by diffusion of protons back into the matrix due to the presence of DNP is released as heat, causing the spike in body temperature. Death by DNP overdoses are likely to be caused by hyperthermia, but a severe reduction of ATP production will also cause problems at the cellular level. Metabolic rates rise because of the mobilization of energy stores - sugars and fats are oxidized at a higher rate to try to compensate for the dissipation of the proton-motive force in the mitochondria.

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