Kaplan Nursing Entrance Practice Exam

Which part of cellular respiration directly produces a pH gradient during the oxidative metabolism of glucose?

1. Glycolysis

2. Krebs cycle

3. Electron transport chain

4. Fermentation

The correct answer is: Electron transport chain

The electron transport chain is responsible for directly creating a pH gradient during the oxidative metabolism of glucose. This process involves a series of protein complexes located in the inner mitochondrial membrane, where electrons are passed along a chain as they are transferred from electron donors such as NADH and FADH2. As electrons move through the chain, energy is released, which is utilized to actively transport protons (H+) from the mitochondrial matrix into the intermembrane space. This action causes a higher concentration of protons in the intermembrane space compared to the matrix, establishing both a pH gradient and an electrochemical gradient, also known as the proton motive force. This proton motive force is crucial for ATP synthesis, as protons flow back into the matrix through ATP synthase, driving the conversion of ADP and inorganic phosphate into ATP. The development of the pH gradient is a fundamental aspect of aerobic respiration, which significantly contributes to the efficient production of ATP compared to anaerobic processes like fermentation or glycolysis, which do not create such a gradient. In summary, the establishment of the pH gradient is a key function of the electron transport chain, making it the correct answer in the context of cellular respiration.