[Campbell Biology P.235] Coenzyme Q CoQ is marketed as 'fuel' for the heart. Based on its bi... | Practice Question

Coenzyme Q CoQ is marketed as 'fuel' for the heart. Based on its biological role in cellular respiration, which statement best critiques this claim?

  • A: CoQ is a direct energy source like glucose, so the claim is accurate.
  • B: CoQ acts as an electron carrier in the electron transport chain, facilitating ATP production, but is not consumed as fuel itself.
  • C: CoQ is an enzyme that synthesizes ATP, making the claim partially true.
  • D: CoQ primarily functions in fermentation pathways, unrelated to cellular fuel.

Explanation

Coenzyme Q Ubiquinone is a lipid-soluble electron carrier within the electron transport chain, specifically transferring electrons from complexes I and II to complex III. It facilitates the flow of electrons down the chain, which drives proton pumping and ultimately ATP synthesis. However, CoQ itself is not consumed or broken down to directly release energy; it acts catalytically. Therefore, calling it a 'fuel' is misleading, as fuels are molecules that are catabolized to produce energy.