Question

NADH and FADH2 is associated with respectively ____________

(a) Complexes I and complex II

(b) Complexes II and complex III

(c) Complexes I and complex III

(d) Complexes III and complex IV

I have been asked this question during an internship interview.

My enquiry is from Mitochondrial Structure and Function topic in section Mitochondrial Structure and Function of Cell Biology

Answer 1

Right choice is (a) Complexes I and complex II

To elaborate: When NADH is the electron donor, electrons enter the respiratory chain via complex I, which transfers electrons to Ubiquinone. FADH2 remains covalently attached to succinate dehydrogenase, a component of complex II. When FADH2 is donor, electron is directly passed to Ubiquinone.