Question

Reduction (Step 2 of Calvin Cycle)

a) Incorporation of CO2 into RuBP
b) Production of G3P
c) Regeneration of RuBP
d) Formation of PGA

Answer 1

The Calvin cycle consists of three stages: fixation, where CO2 is fixed to RuBP by the enzyme RuBisCO; reduction, where 3-PGA is reduced to G3P using ATP and NADPH; and regeneration, where G3P is used to regenerate RuBP, allowing the cycle to continue.

Step-by-step explanation:

The Calvin Cycle and Its Stages

The Calvin cycle is a set of biochemical reactions that take place in the stroma of chloroplasts in photosynthetic organisms. It is also referred to as the light-independent reactions or dark reactions. The cycle can be organized into three basic stages: fixation, reduction, and regeneration.

• Fixation: The enzyme RuBisCO incorporates carbon dioxide (CO2) into an organic molecule called ribulose bisphosphate (RuBP). This process results in the formation of 3-phosphoglycerate (3-PGA).
• Reduction: The 3-PGA is then reduced to glyceraldehyde-3-phosphate (G3P) using electrons from NADPH. This is the stage where ATP and NADPH are used to reduce CO2, and hence, contribute to the production of carbohydrate molecules from G3P.
• Regeneration: Finally, G3P is used to regenerate RuBP, allowing the cycle to continue. Of the G3P molecules produced, only a portion exit the cycle to contribute to the formation of other compounds, such as glucose. The remainder of the G3P molecules are used to regenerate RuBP, with the use of additional ATP.

The Calvin cycle must be completed multiple times to produce a single molecule of glucose. Specifically, it requires six turns to produce one six-carbon glucose molecule, as each turn fixes one molecule of CO2.