In mitochondria, the rate of electron transfer is tightly coupled to the demand for ATP. When the rate of use of ATP is relatively low, the rate of electron transfer is low; when demand for ATP increases, electron‑transfer rate increases. Under these conditions of tight coupling, the number of ATP molecules produced per atom of oxygen consumed when NADH is the electron donor, the P/O ratio, is about 2.5. Predict what would happen when an uncoupling agent, such as 2,4‑dinitrophenol, is added to an actively respiring tissue preparation. The rate of oxygen consumption

The correct answer will be - P/O decreases

Explanation:

The uncoupling agents are the chemical drugs which uncouple the two different process of cellular respiration which is the electron transport chain from the oxidative phosphorylation or ATP synthesis.

The synthesis of one ATP requires two electrons on the basis of which ATP production / oxygen atom or P/O ratio is calculated.

When 2,4‑dinitrophenol uncouples the ATP synthesis from electron transport chain, then demand of oxygen for the synthesis of ATP increases which result in the decrease in the value of the P/O ratio.

Thus, P/O decreases are the correct answer.