Which of the following does not occur during the Calvin cycle?
a. Carbon fixation
b. Oxidation of NADPH
c. Release of oxygen
d. Regeneration of the CO₂ acceptor

Verified step by step guidance

1. Understand the Calvin cycle: The Calvin cycle is a series of biochemical reactions that take place in the stroma of chloroplasts in photosynthetic organisms. It is also known as the light-independent reactions or dark reactions.
2. Identify the main phases of the Calvin cycle: The Calvin cycle consists of three main phases: carbon fixation, reduction phase, and regeneration of the CO2 acceptor (ribulose bisphosphate, RuBP).
3. Analyze each option: a) Carbon fixation involves the incorporation of CO2 into organic molecules. b) Oxidation of NADPH is part of the reduction phase where NADPH donates electrons. c) Release of oxygen is not part of the Calvin cycle; it occurs during the light-dependent reactions. d) Regeneration of the CO2 acceptor involves the conversion of G3P back into RuBP.
4. Determine which process is not part of the Calvin cycle: Compare each option with the phases of the Calvin cycle to identify the one that does not occur.
5. Conclude that the release of oxygen is not part of the Calvin cycle, as it is associated with the light-dependent reactions of photosynthesis, not the Calvin cycle itself.

Key Concepts

Calvin Cycle

The Calvin Cycle is a series of biochemical reactions that occur in the stroma of chloroplasts in photosynthetic organisms. It is part of the light-independent reactions of photosynthesis, where carbon dioxide is fixed into glucose using ATP and NADPH produced in the light-dependent reactions. The cycle includes carbon fixation, reduction phase, carbohydrate formation, and regeneration of the CO2 acceptor.

Carbon Fixation

Carbon fixation is the process of converting inorganic CO2 into organic compounds during photosynthesis. In the Calvin Cycle, CO2 is fixed by the enzyme RuBisCO, forming 3-phosphoglycerate. This step is crucial for synthesizing glucose and other carbohydrates, providing energy and structural components for the plant.

Oxidation of NADPH

NADPH is a reducing agent used in the Calvin Cycle to convert 3-phosphoglycerate into glyceraldehyde-3-phosphate. The oxidation of NADPH involves transferring electrons to intermediates in the cycle, facilitating the reduction phase. This process is essential for synthesizing carbohydrates but does not involve the release of oxygen, which occurs in the light-dependent reactions.