Calvin cycle

basics of calvin benson cycle

1. Basics of Calvin Cycle Umair Rasool Azmi

2. Calvin cycle or C3 Cycle or dark reactions Calvin cycle also called as dark reactions is a series of reactions that occur in stroma of the chloroplast. The plants that use calvin cycle for the fixation of carbon dioxide are known as Calvin or C3 Plants for example cotton, rice, wheat, potato etc. It consists of three steps: Carbon fixation Reduction Regeneration

3. Calvin Cycle: Carbon fixation Carbon dioxide enters through the stomata of chloroplasts C ombines with ribulose 1,5 bisphosphate (RuBP), a five carbon sugar. Rubisco is an enzyme that catalyzes this reaction. As a result, a 6-carbon compound is formed which immediately breaks into two molecules of 3-carbon phosphoglyceric acid molecules (3PGA). Due to this fact that a 3-carbon molecule is first stable molecule in this reaction, this reaction is called as C3 pathway.

4. Calvin Cycle: Reduction Six molecules of 3PGA are phosphorylated (Production of ATP from of ADP and inorganic phosphorus) by 6 molecules of ATP. As a result, six molecules of 1,3 diphosphoglyceric acid and six ADP`s are produced. These six molecules of 1,3 diphosphoglyceric acid are reduced by six molecules of NADPH2 to form six molecules of 3-phosphoglyceraldehydes (G3P).

5. Calvin Cycle : Regeneration In this phase, ribulose 1,5 biphosphate (RuBP) is regenerated by using some of 3-phosphoglyceraldehydes.

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