alleryStart learning →If pyruvate kinase is not present in sufficient quantity, what happens to glycolysis?
AThe pathway reverses and rebuilds glucose
BThe pathway moves into the mitochondrion
CThe whole pathway stops at the first step
DThe pathway runs but yields two ATP less
Answer & Solution
Correct answer: D. The pathway runs but yields two ATP less
1. Pyruvate kinase catalyses the last step of glycolysis, the one that forms pyruvate.
2. If it is not available in sufficient quantities, that final step will not occur.
3. The entire pathway still proceeds, but only two adenosine triphosphate molecules are made in the second half.
4. Normally the second half makes four, so the shortfall is two.
5. Pyruvate kinase is therefore a rate-limiting enzyme for glycolysis.
6. Nothing about a missing final enzyme moves the pathway into a mitochondrion, since glycolysis is a cytoplasmic pathway throughout.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.2 Glycolysis_
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