AAMC FL Practice Exam

What is required for ATP production during chemiosmosis?

1. Carbon dioxide diffusion

2. Movement of H+ ions across the membrane

3. Hydrolysis of glucose

4. Reduction of NADH

The correct answer is: Movement of H+ ions across the membrane

For ATP production during chemiosmosis, the movement of H+ ions across the membrane is essential. In the process of chemiosmosis, which is a part of cellular respiration and photosynthesis, a proton gradient is established across a membrane. This gradient, created by the activity of electron transport chains, results in a higher concentration of hydrogen ions (H+) on one side of the membrane compared to the other. As H+ ions flow back across the membrane, typically through an enzyme known as ATP synthase, the energy released from this movement is harnessed to synthesize ATP from ADP and inorganic phosphate. This mechanism is crucial because it couples the energy derived from the proton gradient, created by previous steps in the respiration or photosynthetic pathway, to the production of ATP, the primary energy currency of the cell. In contrast, the other choices do not directly relate to ATP production via chemiosmosis. For instance, carbon dioxide diffusion is not involved in the creation of the proton gradient needed for ATP synthesis. Hydrolysis of glucose pertains to glycolysis and does contribute to overall energy production, but it does not involve the chemiosmotic process itself. Similarly, while the reduction of NADH does play a role in energy metabolism, it is separate