Question

Select the three steps of the Calvin cycle from the options listed here.

Answer 1

The three steps of the Calvin cycle are fixation, reduction, and regeneration. In fixation, carbon dioxide combines with RuBP to form 3-PGA. In reduction, 3-PGA is converted into G3P using ATP and NADPH. In regeneration, G3P is used to regenerate RuBP.

Step-by-step explanation:

The three steps of the Calvin cycle are fixation, reduction, and regeneration.

1. Fixation: In this step, carbon dioxide (CO₂) combines with ribulose bisphosphate (RuBP) in the presence of the enzyme RuBisCO to form an unstable 6-carbon intermediate. This intermediate quickly splits into two 3-carbon molecules called 3-phosphoglycerate (3-PGA).
2. Reduction: In this step, ATP and NADPH from the light reactions are used to convert the 3-PGA molecules into a molecule called glyceraldehyde-3-phosphate (G3P). Some of the G3P molecules are used to produce glucose and other sugars, while others are used to regenerate RuBP.
3. Regeneration: In this step, some of the G3P molecules produced in the reduction step are used to regenerate RuBP, the molecule that initiates the Calvin cycle. This step requires ATP.