TBR Bio Error/Faulty Attempt At Trickery

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Dec 1, 2011
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TBR Bio Chapter 1 Passage 6 Question 38
This might be hard to answer without the passage, but my question primarily comes from what seems to be a faulty question/answer/explanation combination. Actually, you shouldn't need the passage unless you don't know cell biology.

According to information in the passage, the concentration gradients of ions are maintained through the Na/K pump. The ultimate source of energy for this pump is:

A. formation of ATP
B. breakdown of ATP
C. oxidation of nutrients
D. reduction of nutrients

Answer: C

Explanation: The pump that transports sodium and potassium ions does breakdown ATP to couple the energy of that reaction to the work it must perform in transporting the ions. However, the question alludes to the ultimate source of the energy. Therefore, we need to think about how we are getting the ATP that is used by this pump. This answer comes from our knowledge of metabolism and an understanding that food is oxidized in the course of glycolysis and the Krebs cycle. The electrons released are eventually transported down the ETC and are coupled to a proton gradient, which results in the formation of ATP. The correct answer is C.

Ok fine, so they were picky about the exact wording of the question. HOWEVER, in order for glycolysis to proceed, ATP must be consumed, so the answer should really be B if TBR wants to get technical about it.

In addition, pyruvate breakdown to oxaloacetic acid is also catalyzed by an ATP dependent reaction.

Likewise, lipolysis requires ATP degredation. I'm not sure about other sources of acetyl-CoA, but I'm sure they require the energy from ATP as well.

In other words, you can oxidize all the nutrients you want, but without ATP breakdown none of the catabolic processes form anything energetically useful.

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i think C is reasonable without getting technical because it's asking "where does our energy come from?"

food, of course.

sleep on it and look at it tomorrow