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Hexose Monophosphate. Hexose Monophosphate. Pentose Phosphate Pathway Glycolysis , TCA, and oxidative phosphorylation are primarily concerned with the generation of ATP. The PPP meets the need of all organisms for a source of NADPH to use in reductive biosynthesis.
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Hexose Monophosphate Pentose Phosphate Pathway • Glycolysis, TCA, and oxidative phosphorylation are primarily concerned with the generation of ATP. • The PPP meets the need of all organisms for a source of NADPH to use in reductive biosynthesis. • The reducing power is NADPH. • There is a fundamental distinction NADH NADPH The direction of HMP depends on the supply and demand for intermediates in the cycle…
Two Major Functions • NADPH • Ribose Overall reaction: 3G-6-P + 6NADP+ 3CO2 + 2G-6-P + Glyceraldehyde-3P + 6NADPH + 6H+ • It occurs in the cytosol because NADP+ is used as a hydrogen acceptor. There are two sequential reactions. • Oxidative • Nonoxidative
Oxidative and Nonoxidative Reactions • In oxidative, G-6-P undergoes dehydrogenation and decarboxylation to give a pentose ribulose-5-P. • In nonoxidative, ribulose 5-P is converted back to G-6-P by a series of reactions involving two enzymes • Transketolase • Transaldolase • Dehydrogenation of G-6-P is the major biological control of the HMP. • G-6-PD is strongly inhibited by NADPH.