[Campbell Biology P.224] Which of the following statements correctly distinguishes ubiquinon... | Practice Question
Which of the following statements correctly distinguishes ubiquinone from cytochromes in the electron transport chain?
A: Ubiquinone is a protein with a heme group, whereas cytochromes are small, hydrophobic, non-protein molecules.
B: Ubiquinone is mobile within the membrane and is not a protein, while cytochromes are proteins containing an iron atom in a heme group.
C: Both ubiquinone and cytochromes are proteins, but only cytochromes contain iron for electron transport.
D: Cytochromes directly pass electrons to oxygen, while ubiquinone only accepts electrons from NADH.
Explanation
The text states that ubiquinone is a small, hydrophobic molecule and the only member of the electron transport chain that is not a protein. It is mobile within the membrane. Cytochromes, on the other hand, are proteins with a heme group containing an iron atom that accepts and donates electrons.