Card 39 / 101: A student argued that aerobic and anaerobic respiration should produce the same amount of energy. He argued that both processes are essentially the same-only the terminal electron acceptor is different. What's wrong with his argument?
A) Nothing-they SHOULD both produce the same amount of energy. Clearly he knows more than his professors or the writers of his textbook.
B) Not all electrons are brought into the electron transport chain with the same amounts of potential energy. NADH, for example, enters the electron transport chain 'further up' than FADH2-so it will lead to less proton motive force being generated, and thus less eventual ATP.
C) Not all electron acceptors are the same-some are closer in terms of electronegativity to their high-energy electron carrier molecules (e.g. NADH) than others. The amount of energy that can eventually be obtained is directly proportional to the degree of difference between the high-energy electron carrier and the eventual terminal electron acceptor. The greater the difference, the greater the energy obtained. Oxygen typically has the highest degree of difference of the terminal electron acceptors utilized.
D) He should believe what his instructors tell him, without question-and they say aerobic respiration is better, so it MUST be so.

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