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

Verified step by step guidance

1. Understand the Calvin cycle: The Calvin cycle is a series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis. It is responsible for converting carbon dioxide (CO₂) into glucose using energy from ATP and NADPH produced in the light-dependent reactions.
2. Review the key processes of the Calvin cycle: The cycle involves three main stages: (1) Carbon fixation, where CO₂ is incorporated into a 5-carbon sugar (ribulose-1,5-bisphosphate or RuBP) by the enzyme RuBisCO; (2) Reduction, where ATP and NADPH are used to convert 3-phosphoglycerate (3-PGA) into glyceraldehyde-3-phosphate (G3P); and (3) Regeneration, where RuBP is regenerated using ATP to continue the cycle.
3. Analyze each option: (a) Carbon fixation is a key step in the Calvin cycle, so it does occur. (b) Oxidation of NADPH occurs during the reduction phase, where NADPH donates electrons to reduce 3-PGA into G3P. (c) Consumption of ATP occurs in both the reduction and regeneration phases. (d) Release of oxygen does not occur in the Calvin cycle; oxygen is released during the light-dependent reactions of photosynthesis, not the Calvin cycle.
4. Identify the correct answer: Based on the analysis, the process that does not occur during the Calvin cycle is the release of oxygen.
5. Conclude: The Calvin cycle is focused on carbon fixation and the synthesis of sugars, and it does not involve the release of oxygen, which is a separate process tied to the splitting of water molecules in the light-dependent reactions.

Key Concepts

Calvin Cycle

The Calvin cycle is a series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis. It is responsible for converting carbon dioxide and other compounds into glucose, utilizing energy from ATP and reducing power from NADPH. The cycle consists of three main phases: carbon fixation, reduction, and regeneration of ribulose bisphosphate.

Carbon Fixation

Carbon fixation is the initial step of the Calvin cycle, where carbon dioxide is incorporated into an organic molecule. This process is catalyzed by the enzyme ribulose bisphosphate carboxylase/oxygenase (RuBisCO), resulting in the formation of 3-phosphoglycerate (3-PGA). It is essential for converting inorganic carbon into a form that can be utilized by living organisms.

Role of NADPH and ATP

NADPH and ATP are crucial energy carriers produced during the light-dependent reactions of photosynthesis. In the Calvin cycle, NADPH provides the reducing power needed to convert 3-PGA into glyceraldehyde-3-phosphate (G3P), while ATP supplies the energy required for various reactions. However, the Calvin cycle does not involve the oxidation of NADPH or the release of oxygen, which distinguishes it from the light-dependent reactions.