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Difficulty: HardGaseous Exchange and Cellular Respiration

During the complete aerobic oxidation of one molecule of glucose in a cell, a total of 10 NADHNADH and 2 FADH2FADH_2 reduced coenzymes are generated across glycolysis, the link reaction, and the Krebs cycle. Assuming that each NADHNADH yields 3 ATP molecules and each FADH2FADH_2 yields 2 ATP molecules during electron transport, what is the net number of ATP molecules produced specifically through oxidative phosphorylation?

  1. A
    38 ATP38\text{ ATP}
  2. B
    30 ATP30\text{ ATP}
  3. 34 ATP34\text{ ATP}Answer
  4. D
    36 ATP36\text{ ATP}

Answer

The net number of ATP molecules synthesized specifically through oxidative phosphorylation is 34 ATP.
Oxidative phosphorylation generates ATP via electron transport and chemiosmosis using reduced coenzymes (NADHNADH and FADH2FADH_2). Multiplying 10 NADHNADH by 3 ATP gives 30 ATP, and multiplying 2 FADH2FADH_2 by 2 ATP gives 4 ATP. Summing these yields exactly 34 ATP.

Step-by-Step Solution

1
Calculate ATP yield from NADH coenzymes via the electron transport chain.
10 NADH×3 ATP/NADH=30 ATP10\text{ NADH} \times 3\text{ ATP/NADH} = 30\text{ ATP}
Each NADH molecule donates electrons to the respiratory chain to pump sufficient protons for generating 3 ATP molecules.
2
Calculate ATP yield from FADH2 coenzymes via the electron transport chain.
2 FADH2×2 ATP/FADH2=4 ATP2\text{ FADH}_2 \times 2\text{ ATP/FADH}_2 = 4\text{ ATP}
FADH2 enters the electron transport chain at a lower energy level (Complex II), yielding 2 ATP molecules per FADH2.
3
Sum the ATP produced by both coenzymes to find total oxidative phosphorylation yield.
30 ATP+4 ATP=34 ATP30\text{ ATP} + 4\text{ ATP} = 34\text{ ATP}
Oxidative phosphorylation refers exclusively to ATP synthesized via chemiosmosis powered by electron transport, separate from substrate-level phosphorylation.

Key Concept

Differentiation between substrate-level phosphorylation and oxidative phosphorylation ATP yields in cellular respiration
Estimated Time:2m 0s
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Topics

Gaseous Exchange and Cellular Respiration

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