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Like the pentose phosphate pathway, these pathways are related to parts of glycolysis. [3] Another carbon metabolism-related pathway involved in the generation of NADPH is the mitochondrial folate cycle, which uses principally serine as a source of one-carbon units to sustain nucleotide synthesis and redox homeostasis in mitochondria.
In contrast, the main function of NADPH is as a reducing agent in anabolism, with this coenzyme being involved in pathways such as fatty acid synthesis and photosynthesis. Since NADPH is needed to drive redox reactions as a strong reducing agent, the NADP + /NADPH ratio is kept very low.
The chemical pathway of oxygenic photosynthesis fixes carbon in two stages: the light-dependent reactions and the light-independent reactions.. The light-dependent reactions capture light energy to transfer electrons from water and convert NADP +, ADP, and inorganic phosphate into the energy-storage molecules NADPH and ATP.
The pentose phosphate pathway. The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt or HMP shunt) is a metabolic pathway parallel to glycolysis. [1] It generates NADPH and pentoses (five-carbon sugars) as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides. [1]
NADP + + 2H + + 2e-→ NADPH + H + This consumes the H + ions produced by the splitting of water, leading to a net production of 1/2O 2, ATP, and NADPH + H + with the consumption of solar photons and water. The concentration of NADPH in the chloroplast may help regulate which pathway electrons take through the light reactions.
The main carboxylating enzyme in C 3 photosynthesis is called RuBisCO, which catalyses two distinct reactions using either CO 2 (carboxylation) or oxygen (oxygenation) as a substrate. RuBisCO oxygenation gives rise to phosphoglycolate , which is toxic and requires the expenditure of energy to recycle through photorespiration .
In cyclic photophosphorylation, cytochrome b 6 f uses electrons and energy from PSI to create more ATP and to stop the production of NADPH. Cyclic phosphorylation is important to create ATP and maintain NADPH in the right proportion for the light-independent reactions. The net-reaction of all light-dependent reactions in oxygenic photosynthesis ...
Transketolase connects the pentose phosphate pathway to glycolysis, feeding excess sugar phosphates into the main carbohydrate metabolic pathways in mammals. Its presence is necessary for the production of NADPH , especially in tissues actively engaged in biosyntheses, such as fatty acid synthesis by the liver and mammary glands , and for ...