Question

With the help of biochemical reactions, explain the various phases of the Calvin cycle.

Answer 1

Calvin cycle is the second phase of the photosynthetic reactions which occurs in the stroma of the chloroplast.

There are 3 phases in this pathway. The first phase is carbon fixation. The enzyme RuBisCo is responsible for the fixation of carbon dioxide which reacts with the primary acceptor RUBP (Ribulose-1,5- bisphosphate). The first stable product is 3- PGA (3-phosphoglyceric acid).

The second step is reduction. 3-PGA is converted to glyceraldehyde-3-phosphate (G3P). ATP and NADPH are used for this reaction.

The third step is formation of glucose molecule. Some of the molecules of G3P are used for the formation of glucose.

The fourth step is regeneration. This is the step when ceratin molecules of G3P are used to regenerate the RUBP for the next cycle.