Why is the Calvin-Benson cycle called reductive pentose phosphate cycle?

1 Answer
Jan 22, 2018

Calvin-Benson cycle is called reductive pentose phosphate cycle because it starts with Ribulose 1-5 diphosphate , a pentose.


Calvin-Benson cycle involves reduction of carbon dioxide and water to form glucose molecule. This reduction is brought about by NADPH2, which is synthesized during light reaction of photosynthesis.

Calvin cycle can occur in absence of light but is dependent upon the end product of light reaction, i.e. NADPH2. It is thus termed dark reaction of photosynthesis.

Calvin cycle starts with ribulose 1-5 di-phosphate, a 5-carbon compound. It combines with carbon dioxide to form di-phospho-glyceric acid . It is reduced to form 2 molecules of Glyceraldehyde-3-phosphate. One molecule of glyceraldehyde-3-phosphate is converted into its isomeric form dihydroxy-acetone phosphate.

Glyceraldehyde-3-phosphate combines with dihydroxyactone phosphate to form fructose 1-6 diphosphate, which is finally converted into glucose