Question

Which is the first stable product formed during the Calvin cycle?

• A. Glyceraldehyde-3-phosphate
• B. 3-phosphoglycerate
• C. Triose phosphate
• D. RuBP

Answer 1

The correct option is B

3-phosphoglycerate

The correct option is Option B.

Explanation for the correct answer:

1. Carboxylation is the first stage in the Calvin cycle.
2. RuBP is carboxylated, and two molecules of 3-phosphoglycerate are formed (3-PGA).

Explanation for the incorrect answer:

Option (A):

1. Glyceraldehyde 3-phosphate (also known as triose phosphate or 3-phosphoglyceraldehyde) is a phosphate of glyceraldehyde.
2. It is the precursor to the production of other carbs.

Option (C):

1. It's a two-component enzyme that catalyzes the conversion of glyceraldehyde-3-phosphate (G-3-P) to dihydroxyacetone-phosphate (DHAP).
2. As a result, during the reduction stage, triose phosphate is generated.

Option (D):

1. It's a ketose sugar with five carbons.
2. RuBP is carboxylated by the enzyme RuBisCO or RuBP carboxylase in the first phase of the Calvin cycle.

Final answer:

3-phosphoglycerate is the first stable product formed during the Calvin cycle.