Question

Explain regulation of calrin cycle.

Answer 1

the calvin cycle or C3 cycle can be described under three stages:

1. carboxylation

2.reduction

3.regeneration

CARBOXYLATION

carboxylation is the fixation of CO2 into a stable organic intermediate. Carboxylation is the most crucial step of the calvin cycle where CO2 is utilised for the carboxylation of RuBP. This reaction is catalysed bythe enzyme RuBP. This reaction is catalysed by the enzyme RuBP carboxylase which results in the formation of two molecules of 3-PGA. Since this enzyme also has an oxygenation activity it would be more correct to call it RuBP carboxylase-oxygenase or RuBisCO.

REDUCTION

These are a series of reaction that lead to the formation of glucose. The steps utilisation of 2 molecules of ATP for phosphorylation and two of NADPH for reduction per CO2 molecule fixed. The fixation of six molecules of CO2 and 6 turns of the cycle are required for the removal of one molecule of glucose from the pathway.

REGENERATION

Regeneration of the CO2 acceptor molecule RuBP is crucial if the cycle is to continue uninterrupted. The regeneration steps requirs one ATP for phosphorylation to form RuBP.