Plant Metabolism.

The first 200 words of this essay...

Louise Weston

Plant Metabolism

To what extent has genetic manipulation of the Calvin cycle forced the reappraisal of our understanding of the control of metabolic pathways in plants? What do studies of transgenic plants reveal about the integration of metabolism?

The Calvin cycle or the reductive pentose phosphate pathway is quantitatively the most important metabolic pathway in biology, which involves 13 reactions catalysed by 11 enzymes in the stroma of the chloroplast. All photosynthetic eukaryotes reduce CO2 to carbohydrate by this same mechanism. The cycle involves CO2 and water from the environment being enzymatically combined with a five carbon accepter molecule; ribulose-1,5-bisphospahte where a total of 3 molecules of ATP and 2 molecules of NADPH produced from the light reactions are consumed for each CO2 molecule converted into carbohydrate. The Calvin cycle proceeds in three stages;

* Carboxylation of the CO2 acceptor, forming two molecules of 3-phosphoglycerate, the first stable intermediate of the Calvin cycle.

* Reduction of 3-phosphoglycerate, forming glyceraldehydes-3-phosphate.

* Regeneration of the CO2 acceptor ribulose-1,5-bisphosphate from glyceraldehydes-3-phosphate.

From the fixation of three molecules of CO2, six molecules of phosphoglycerate are formed and are converted to six molecules of glyceraldehydes-3-phosphate (triose