The Three Stages Of The Filvin Cycle And The Calvin Cycle

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The C3 pathway is the Calvin cycle. The Calvin cycle has three stages. The first stage is when carbon dioxide enters into the Calvin cycle and is bonded to RuBP. This form a six carbon molecule which is further broken down create two PGA’s with three carbons. RuBP is important because of the carbon fixation that it performs. However it is more attracted to oxygen which leads to cellular respiration. In the second stage of the Calvin cycle PGA is further broken down into PGAL. In the third stage of the Calvin cycle five of the six generated molecules of glyceraldehyde get used to regenerate RuBP. The Calvin cycle requires more ATP than NADPH but both of the molecules are used. Fixed carbon is generally converted to sucrose or starch. Both are food for the plant where sucrose is readily available for the plant starch is stored and requires enzymatic activity to break down into a usable form. Photorespiration occurs when the stoma of the plant is closed and RuBP binds with oxygen rather than carbon dioxide. This is problematic because photorespiration is generally less effective than carbon fixation. The C4 pathway produces the molecule oxaloacetate. Oxaloacetate is a four carbon molecule. C4 plants use both the C4 pathway and the Calvin cycle. To form oxaloacetate carbon dioxide is first fixed to PEP. PEP carboxylase then breaks down the molecule to form oxaloacetate. Oxaloacetate is then broken down into malate and aspartate. For aspartate to form an amino group must be

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