Question

Choose the correct combination of labelling the carbohydrate molecule involved in the Calvin cycle.

• A. A- RuBP, B-Triose phosphate, C-PGA
• B. A-PGA, B-RuBP, C-Triose phosphate
• C. A-PGA, B-Triose phosphate, C-RuBP
• D. A-RuBP, B-PGA, C-Triose phosphate
• E. A-Triose phosphate, B-PGA, C-RuBP

Answer 1

The correct option is D A-RuBP, B-PGA, C-Triose phosphate

The given flowchart is a representation of the calvin cycle.
In this pathway, ribulose 1,5-biphosphate (RuBP,A) gets carboxylated to form phosphoglyceric acid (PGA, B).
PGA, which contains 3 carbon atoms, is the first stable compound formed after carbon fixation.
Hence, calvin cycle is also called C3 cycle.
PGA undergoes reduction to form triose phosphate (C), which is broken down to regenerate RuBP.