Why does NADH and FADH2 donate their H + to the electron transport chain readily?

a. Because they have a high affinity for the H+

b. Because they have a low affinity for the H+

c. Because the H + add stability to their structures

d. All of the above

b. Because they have a low affinity for the H+

Explanation:

All electrons that enter the transport chain come from NADH and FADH2 molecules that are produced in earlier phases of cellular respiration: glycolysis, pyruvate oxidation and the citric acid cycle.

NADH is very good at donating electrons in redox reactions (that is, its electrons are at a high energy level), so you can transfer your electrons directly to complex I and transform it back into NAD +. The movement of electrons through complex I in a series of redox reactions releases energy, which the complex uses to pump protons from the matrix into the intermembrane space.

FADH2 is not as good for donating electrons as NADH (that is, its electrons are at a lower energy level), so it cannot transfer its electrons to complex I. Instead, it introduces electrons to the transport chain through complex II, which does not pump protons through the membrane.