Kaplan Nursing Entrance Practice Exam

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

1. Cytoplasm

2. Krebs cycle

3. Electron transport chain

4. Glycolysis

The correct answer is: Electron transport chain

The electron transport chain is responsible for producing a pH gradient during glucose metabolism. This process occurs in the inner mitochondrial membrane, where electrons are transferred through a series of protein complexes. As electrons move down the chain, energy is released, which is used to pump protons (H+ ions) from the mitochondrial matrix into the intermembrane space. This pumping action creates a concentration gradient of protons, leading to a difference in pH between the two compartments. The accumulation of protons in the intermembrane space creates potential energy, known as the proton motive force. This force is crucial for ATP synthesis, as protons flow back into the mitochondrial matrix through ATP synthase, driving the conversion of ADP and inorganic phosphate into ATP. In contrast, the other parts of cellular respiration—such as the cytoplasm, Krebs cycle, and glycolysis—do not generate a pH gradient in the same manner. Glycolysis and the Krebs cycle primarily involve the breakdown of glucose and the production of electron carriers, without contributing to the establishment of a proton gradient. The overall energy transfer and ATP production rely heavily on the actions occurring within the electron transport chain, establishing it as the vital step that produces the pH gradient crucial for effective cellular respiration