Calvin Cycle I

Carbon Assimilation Reaction ( Calvin Cycle )

Dark reaction is not that dark. It is thought as independent of light, but it turns out that it is indirectly controlled by light reaction.

In dark Calvin cycle does not occur to a significant extent.

3 stages of Calvin cycle :

First stage : CO₂ fixation ; 3C₅ + 3C₁ ---- 6C₃

Second stage : Reduction 3-GP ----- G-3-P

Third stage : Generation of receptor C₅

C3 + C3 --- C6

C6 + C3 --- C5 + C4

C4 + + C3 --- C7

C7 + C3 --- C5 + C5

C3 – Glyceraldehyde – 3- phosphate and DHAP

C4 – erythrose – 4- phosphate

C5 - Xylulose – 5 – P; Ribose – 5- P; Ribulose-5-P; Ribulose-1,5-BP

C7 – Sedoheptulose-1,7-BP, Sedoheptulose-7-P

C6 – F-1,6-BP; F-6-P

9 ATP and 6 NADPH are required for fixing 3 molecules of CO₂ ; in the same ratio they are produced in light reaction.