Q3.9. For which of the following is potential energy DECREASING? (Hint: Click here to see an overview of the ETC.) Protons moving from the mitochondrial matrix to the intermembrane space O ADP gaining a phosphate group to become a molecule of ATP Two protons being moved closer toward each other O Electrons moving from Complex IV to Oâ‚‚ None
The correct answer and explanation is:
To determine where potential energy is decreasing, let’s analyze each scenario in the context of potential energy and biological processes:
- Protons moving from the mitochondrial matrix to the intermembrane space:
- This is an active process where protons are pumped against their concentration gradient during the electron transport chain (ETC). Moving protons against the gradient increases potential energy, so this is not the correct answer.
- ADP gaining a phosphate group to become a molecule of ATP:
- The formation of ATP from ADP and inorganic phosphate is an endergonic process, meaning it requires energy and increases potential energy. This is also not the correct answer.
- Two protons being moved closer toward each other:
- Protons are positively charged, and like charges repel each other. Bringing them closer together increases the repulsive electrostatic force, thus increasing potential energy. This is not correct either.
- Electrons moving from Complex IV to O₂:
- In the ETC, electrons move from high-energy states to lower-energy states as they pass through complexes and eventually combine with oxygen. When electrons move to oxygen (a highly electronegative molecule), they lose potential energy. This is the correct answer.
Correct Answer:
Electrons moving from Complex IV to O₂