Question

What would happen to the electron transport system (ETS) and oxidative phosphorylation pathway in the presence of excess NADH if the mitochondrial matrix were not closed, but opened up to the cytoplasm?

Answer 1

ETS: It would function normally and would oxidize NADH into NAD+

Oxidative phosphorylation: It would not synthesize ATP

Step-by-step explanation:

Under normal conditions, the inner mitochondrial membrane does not allow the protons to cross it. As electrons are passed from NADH to the electron carriers of ETC, the protons are pumped into the intermembrane space. This makes the intermembrane space more acidic and has a higher concentration of protons than the matrix. The resultant proton concentration gradient is used to drive ATP synthesis.

If the matrix was opened up to cytoplasm, NADH would be oxidized normally by giving its electrons to the molecular oxygen. However, the proton concentration gradient would be dissipated due to the diffusion of protons towards the cytoplasm. It would not allow ATP synthesis by oxidative phosphorylation.