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Difficulty: EasyGaseous Exchange and Cellular Respiration

During cellular respiration, a single molecule of glucose undergoes glycolysis in the cytoplasm of a cell. What is the net yield of ATP molecules produced directly during this initial pathway?

  1. 2 ATP moleculesAnswer
  2. B
    4 ATP molecules
  3. C
    36 ATP molecules
  4. D
    38 ATP molecules

Answer

2 ATP molecules
Glycolysis splits one glucose molecule into two pyruvate molecules. Although 4 ATP molecules are produced during the energy payoff phase, 2 ATP molecules are consumed during the initial preparatory phase, resulting in a net gain of 2 ATP molecules per glucose molecule.

Step-by-Step Solution

1
Identify energy consumption in the activation phase of glycolysis.
2 ATP molecules are consumed to phosphorylate glucose into fructose-1,6-bisphosphate.
Energy investment is required to initiate glucose breakdown.
2
Identify energy generation in the payoff phase of glycolysis.
4 ATP molecules are synthesized via substrate-level phosphorylation.
Enzymatic conversion yields direct ATP synthesis.
3
Calculate the net ATP yield.
4 ATP produced − 2 ATP consumed = 2 ATP net yield.
Net energy yield equals total ATP synthesized minus total ATP invested.

Key Concept

Net ATP yield during glycolysis
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Topics

Gaseous Exchange and Cellular Respiration

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