place in stroma of mesophyll cells, where the CO acceptor molecule is -Carbon compound, phospho enol pyruvate (PEP) to form -carbon Oxalo acetic acid (OAA). The first product is a -carbon and so it is named as C cycle. oxalo acetic acid is a dicarboxylic acid and hence this cycle is also known as dicarboxylic acid pathway (Figure . ).
Carbon dioxide fixation takes place in two places one in mesophyll and another in bundle sheath cell (di carboxylation pathway). It is the adaptation of tropical and sub tropical plants growing in warm and dry conditions. Fixation of CO with minimal loss is due to absence of photorespiration. C plants require ATP and NADPH H to fix one molecule of CO .
Phase – Glycolytic Reversal / Reduction Phospho glyceric acid is phosphorylated by ATP and produces , bis phospho glyceric acid by PGA kinase. , bis phospho glyceric acid is reduced to glyceraldehyde Phosphate (G- -P) by using the reducing power NADPH H . Glyceraldehyde phosphate is converted into its isomeric form di hydroxy acetone phosphate (DHAP). PGA , bisphosphoglyceric acid PGA Kinase ATP ADP , bisphosphoglceric acid Glyceraldehyde- -Phosphate NADPH H NADP Phase – Regeneration Regeneration of RUBP involves the formation of several intermediate compounds of -carbon, -carbon, -carbon and - carbon skeleton.
Fixation of one carbon dioxide requires ATPs and NADPH H , and for the fixation of CO requires ATPs and NADPH H during C cycle. One carbon compound is the net gain to form hexose sugar. ATP ADP RU5P RUBP Overall equation for dark reaction: 6CO 18ATP 12NADPH H C H O 6H O 18ADP 18Pi 12NADP RUBISCO – RUBP Carboxylase Oxygenase enzyme, is the most abundant protein found on earth. It constitutes % of the chloroplast protein.
It acts as carboxylase in the presence of CO and oxygenase in the absence of