Question

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Compare and contrast the reactions of the Citric Acid Cycle of Cellular Respiration with the reactions in the Calvin Cycle of Photosynthesis?

[Possible topics to include in your essay are (but not limited to): what are the starting molecules and end products of each, where do the processes occur, and what is the overall chemical process (oxidation or reduction).]

Answer 1

1.The citric acid cycle is a part of aerobic respiration and involves the formation of acetyl COA from pyruvate by enzyme pyruvate carboxylase.It involves the oxidation of oxaloacetic acid by acetyl COA which is catalysed by citrate syntase which is the first reaction of the pathway whereas the Calvin cycle is involved in the process of photosynthesis and involves the reduction of carbon dioxide the most oxidised form of carbon to least oxidised form.The Ist reaction involves the carboxylation of carbon dioxide to phosphoglycerate which is catalysed by Rubisco.Hence Calvin cycle occur in organisms which have chlorophyll i.e. plants ,algae whereas calvin cycle occurs in almost all aerobic organism.

2.The citric cycle occurs in cytoplasma and its aim is the formation of energy rich molecules like ATP,NADH and FADH.Which are synthesized to help in the formation of proton gradient in electron transport chain(ETC) whereas calvin cycle occurs in stroma of chloroplast and involves the utilizati of high energy rich compounds like ATP,NADPH to fix carbon dioxide and these copounds where formed by ETC.

3.The citric cycle is oxidative cycle divided into codensation of acetyl COA its oxidation and finally its regeneration for another cycle so end product is acetyl COA whereas Calvin cycle is reduction cycle divided into carboxylation of carbon dioxide its reduction(formation of fixed triose phosphate) and final regeneration of 5 carbon acceptor molecule which is the final product of cycle for the continuation of cycle.