As a result of the oxidation of NADH, what happens to the proton (H+) concentration in the inter membrane space?
A. It decreases
B. It increases
C. It doesn’t change
The correct answer and explanation is:
The correct answer is B. It increases.
Explanation:
The oxidation of NADH occurs during cellular respiration, specifically in the electron transport chain (ETC) within the mitochondria. NADH donates electrons to Complex I of the electron transport chain. As the electrons are passed along the chain, energy is released, and this energy is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space.
Here’s the process in more detail:
- NADH Oxidation: NADH, produced in earlier stages like glycolysis and the citric acid cycle, loses its electrons at Complex I of the ETC. NADH is oxidized to NAD+ in this step.
- Proton Pumping: The energy from the electrons passing through the electron transport chain complexes (I, III, and IV) is used to actively pump protons (H+) from the mitochondrial matrix into the intermembrane space. This creates a proton gradient across the inner mitochondrial membrane.
- Proton Gradient: The movement of protons into the intermembrane space results in an increase in proton concentration in that space. This creates both a concentration gradient and an electrochemical gradient (the proton motive force) that drives ATP synthesis via ATP synthase.
- ATP Synthase: The protons then flow back into the matrix through ATP synthase, which uses this flow to synthesize ATP, a process known as oxidative phosphorylation.
As the oxidation of NADH leads to proton pumping into the intermembrane space, the proton concentration increases, which is a critical step in producing ATP and maintaining cellular energy. Therefore, the proton concentration in the intermembrane space increases as a result of NADH oxidation.