Question

Working in a lab you design a gene-knock out for NADH dehydrogenase complex, and therefore the mRNA for this protein is not synthesized. How does your new NADH dehydrogenase-less gene influence the production of ATP from FADH2?

A) ATP production from FADH2 will increase
B) ATP production from FADH2 will initially increase, than drastically decrease
C) ATP production from FADH2 will initially decrease, than drastically increase
D) ATP production from FADH2 will not be affected from this gene
knockout

Answer 1

Knocking out the NADH dehydrogenase complex will not affect ATP production from FADH2, because FADH2 is oxidized starting at complex II in the electron transport chain, which operates independently from complex I.

Step-by-step explanation:

You are asking about the effect of knocking out the NADH dehydrogenase complex on the production of ATP from FADH2. The NADH dehydrogenase complex is the first complex in the electron transport chain (ETC) of mitochondrial oxidative phosphorylation. If mRNA for this protein complex is not synthesized, NADH cannot be oxidized in the ETC. This means that the electrons from NADH cannot enter the ETC to pump protons across the mitochondrial membrane, which drives ATP synthesis.

However, FADH2 donates electrons further down the ETC, beginning at complex II which is succinate dehydrogenase, and not at complex I where NADH dehydrogenase operates. Hence, ATP production from FADH2 will not be affected by the knockout of NADH dehydrogenase, because FADH2 oxidation does not involve complex I, and it can still proceed normally. Therefore, the correct answer to your question is D) ATP production from FADH2 will not be affected by this gene knockout.