Kamis, 10 Oktober 2013

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C-4 Pathway-Food Involving Light and Dark Reaction

Some plants do preparation towards Calvin cycle which is also known as C-4 pathway. It is called C-4 pathway because the product from carbon dioxide fixation is 4 carbon molecules. in this reaction, carbon dioxide fixation is done by phosphoenolpyruvate (PEP, 3 carbon compounds). The fixation result forms oxaloacetate acid (OAA, 4 carbon molecules). The carbon dioxide fixation by PEP is catalyzed by PEP carboxylase which has stronger bind to carbon dioxide than to RUBP carboxylase.

Photosynthesis summary. Photosynthesis is a process to synthesize food involving light and dark reaction

Then, OAA is converted into malate acid, and in mesophyll, it diffuses to bundle sheath where pynrvic acid is formed by releasing carbon dioxide. pyruvic acid, with the help of ATP, is broken down into PEP and will be reused on C4 pathway in mesophyll. Meanwhile, carbon dioxide entering Calvin cycle forms glucose which is then caried throughout the body plants. The examples of C4 plant are grass, corn, and sugar cane.

Structure of corn leaf and mechanism of C-4 synthesis or C4 pathway
Source Essential Biology, 2006

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