Question

Give the schematic representation of calvin cycle.

Answer 1

Calvin Cycle takes place in stroma. For this reaction, light is not essential. It is a biochemical reaction in which CO${}_2$ is fixed with the help of ATP and NADPH${}_2$ formed in light reaction, to form carbohydrates. There are three main steps of calvin cycle are:

• Carboxylation: Three molecules of additive 6C compound immediately split up by hydrolysis into six molecules of 3C compound called 3-phosphoglyceric acid (3-PGA). At first stable product is 3C compound the plants performing calvin cycle are called C3 plants.
• Reduction: One molecule of 3-PGAL, a triose sugar can be directly used for metabolism of the plant or it can be converted into hexose sugar and is ultimately stored in the form of starch.
• Regeneration: Five molecules of 3_PGAL (3C0 are converted into 3 molecules of RuMP (5C) through intermediate products like erythrose and sedoheptulose to continue the cycle. RuMP molecules are then phosphorylated to RuBP.

Thus, for the formation of one molecule of glucose, 18 molecules of ATP and 12 molecules of NADPH${}_2$ are required; and totally 6 calvin cycle are necessary.