Multiple Choice
In the citric acid (Krebs) cycle, how many ATP molecules are produced directly (as substrate-level phosphorylation) per turn of the cycle for each acetyl-CoA that enters?
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Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism
Citric Acid Cycle 1
Multiple Choice
In cellular respiration, what is the main function of the Krebs (citric acid) cycle?
A
To convert glucose into two molecules of pyruvate in the cytosol
B
To use oxygen as the terminal electron acceptor to form water
C
To oxidize acetyl-CoA to while generating reduced electron carriers (NADH and FADH) for the electron transport chain
D
To directly produce most of the cell's ATP by substrate-level phosphorylation
Verified step by step guidance1
Understand the overall role of the Krebs (citric acid) cycle in cellular respiration, which occurs in the mitochondrial matrix and is central to energy metabolism.
Recognize that the Krebs cycle takes acetyl-CoA, a two-carbon molecule derived from pyruvate, and oxidizes it to carbon dioxide (CO\_2).
Identify that during this oxidation process, the cycle generates reduced electron carriers: NADH and FADH\_2, which are crucial for the next stage of cellular respiration, the electron transport chain.
Note that the electron transport chain uses these reduced carriers to produce ATP through oxidative phosphorylation, rather than the Krebs cycle producing most ATP directly.
Conclude that the main function of the Krebs cycle is to oxidize acetyl-CoA to CO\_2 while producing NADH and FADH\_2, which feed electrons into the electron transport chain for ATP generation.
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