Question

(in a few short sentences) Explain why 10 protons are pumped into the intermembrane space of the mitochondria when NADH donates its electrons to the electron transport chain and why only 6 protons are pumped into the intermembrane space of the mitochondria when FADH donates its electrons to the electron transport chain.

Answer 1

Question:

Explain why 10 protons are pumped into the intermembrane space of the mitochondria when NADH donates its electrons to the electron transport chain and why only 6 protons are pumped into the intermembrane space of the mitochondria when FADH donates its electrons to the electron transport chain.

Answer:

In Electron Transport chain using NADH as substrate 2 electrons from NADH molecules transported through NADH dehydrogenase ( complex I) resulting in the pumping of 4 protons into the perimitochondrial space. then the electrons pass trough complex III and complex IV producing additional 6 protons to be pumped into the perimitichondrial space. thus a total of 10 protons which are then pumped into the mitochondrial matrix using complex V or ATP synthase and by the rotational catalysis and produce 3 ATP molecule.

The FADH₂ molecule produced during the Citric acid cycle enters into the complex II (Succinate dehydrogenase). It is located in the inner mitochondrial membrane. It does not pump protons into the perimitichondrial space as other enzyme complexes located in the inner mitochondrial membrane. The electrons from complex II is passed to complex II and so on. in other words, the electrons produced from FADH₂ molecule bypasses the complex I and thus produce only 6 protons which in turn synthesize only 2 ATP molecule.