The second stage of photosynthesis, not requiring light to occur, and during which energy released from ATP drives the production of organic molecules from carbon dioxide is known as dark reaction.The dark reaction occurs outside of the thylakoids. In this reaction, the energy from ATP and NADPH are used to fix carbon dioxide (CO2). The products of this reaction are sugar molecules and other organic molecules necessary for cell function and metabolism. Note that the dark reaction takes place in the stroma (aqueous fluid surrounding the stacks of thylakoids) and the cytoplasm.
The cycle of reactions ( the Calvin cycle) which occurs in the second phase of photosynthesis and does not require the presence of light. It involves the fixation of carbon dioxide and its reduction to carbohydrate and the dissociation of water molecule using energy (ATP ) which is stored during light reaction.It can be of two types one in which a 3 carbon acid phospho gyceric acid that is the C3 pathway. and the other in which the first stable product is a 4 carbon acid i.e. oxaloacidic acid is formed.
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