5 - ATP Yield of ET/ OxPhos

What is the theoretical ATP yield per mole of NADH/H⁺ oxidized by the ETC?

The theoretical yield is 3 ATP per 1 NADH oxidized.

What is the actual ATP yield per mole of NADH/H⁺ oxidized by the ETC?

The actual yield is about 2.5 ATP per 1 NADH.
This accounts for membrane leakiness, slippage, and energy costs of transporting ADP, Pi, and ATP.

What is the theoretical ATP yield per mole of FADH₂ oxidized by the ETC?

The theoretical yield is 2 ATP per 1 FADH₂ oxidized.

What is the actual ATP yield per mole of FADH₂ oxidized by the ETC?

The actual yield is about 1.5 ATP per 1 FADH₂.

Why is ATP yield from FADH₂ lower than that from NADH?

FADH₂ donates electrons to Complex II, which does not pump protons, resulting in less proton gradient and thus less ATP synthesized.

What other process utilizes the proton gradient created by the ETC?

The transport of ADP, ATP, and Pi across the inner mitochondrial membrane also depends on the proton gradient.

How does the proton gradient facilitate ADP/ATP and Pi transport?

• Adenine nucleotide translocase exchanges ADP³⁻ (in) for ATP⁴⁻ (out) using the charge difference maintained by the proton gradient.

• Phosphate translocase co-transports H₂PO₄⁻ and H⁺ into the matrix using the proton-motive force.