AAMC FL Practice Exam

What is the result of electron flow during oxidative phosphorylation?

1. It decreases the pH of the mitochondrial matrix

2. It pumps H+ ions into the intermembrane space

3. It produces glucose from carbon dioxide

4. It generates lactic acid

The correct answer is: It pumps H+ ions into the intermembrane space

The flow of electrons during oxidative phosphorylation is a crucial process that occurs in the inner mitochondrial membrane, primarily involving the electron transport chain. As electrons are transferred through a series of protein complexes, there is a coupling of these electron movements to the transport of protons (H+ ions) across the membrane. This process effectively creates an electrochemical gradient, as protons are pumped from the mitochondrial matrix into the intermembrane space. The pumping of H+ ions not only contributes to a difference in proton concentration but also establishes a membrane potential, known as the proton motive force. This gradient is essential for ATP synthesis, as protons then flow back into the matrix through ATP synthase, driving the conversion of ADP and inorganic phosphate into ATP. The other options present processes that do not occur as a direct result of electron flow during oxidative phosphorylation. For instance, decreasing the pH of the mitochondrial matrix is not directly related; rather, the pH decreases in the intermembrane space due to increased H+ concentration. Producing glucose from carbon dioxide is associated with photosynthesis rather than cellular respiration, and generating lactic acid is typically a result of anaerobic metabolism, not oxidative phosphorylation. Thus, the correct understanding is that the pumping of H+ ions