Asked in Premeth Test 10 — Bioenergetics, Acellular Life and Circulation (12 March 2025) 2025Moderate

Out of the 6 molecules of G3P, how many molecules are used to make glucose?

Correct answer: A. 1

  • A. 1
  • B. 3
  • C. 4
  • D. 5

Explanation

In the Calvin cycle, six molecules of Glyceraldehyde 3-phosphate (G3P) are produced. Out of these, only one molecule exits the cycle and is used to synthesize glucose or other carbohydrates, such as sucrose or starch. The remaining five G3P molecules are recycled to regenerate three molecules of Ribulose bisphosphate (RuBP), which is essential for the continuation of the Calvin cycle. This is why Option A is correct. Options B, C, and D are incorrect as they suggest that more than one G3P molecule is used for glucose production, which is not the case in the Calvin cycle.

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About Cellular Respiration

Cellular respiration releases energy from glucose through glycolysis, the link reaction, the Krebs cycle and the electron transport chain, producing ATP. The pathway differs in oxygen availability: aerobic respiration uses oxygen and yields more ATP, while anaerobic respiration produces much less ATP and forms lactic acid in muscles or ethanol and carbon dioxide in yeast.

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