Pentose phosphate pathway stoichiometry

The hexose monophosphate pathway has several names just to confuse you. It s called the hexose monophosphate shunt or pathway (HMP shunt or pathway), or the pentose phosphate pathway, or the phospho-gluconate pathway (Fig. 15-1). The pathway in its full form is complicated and has complicated stoichiometry. Usually it s not necessary to remember all of it. The important points are that it makes NADPH for biosynthesis and riboses (C-5 sugars) for DNA and RNA synthesis. 

The resultant NADPH and ATP provide the reducing power and free energy to drive the reduction of carbon dioxide (the dark reactions) via the pentose phosphate pathway (or Calvin cycle l7>) and lead ultimately to the synthesis of glucose according to the overall stoichiometry below. 

Mode 2. The needs for NADPH and ribose 5-phosphate are balanced. The predominant reaction under these conditions is the formation of two molecules of NADPH and one molecule of ribose 5-phosphate from one molecule of glucose 6-phosphate in the oxidative phase of the pentose phosphate pathway. The stoichiometry of mode 2 is... 

Summary of the pentose phosphate pathway. This diagram is intended to show the two major parts of the pathway oxidation and decarboxylation of glucose-6-phosphate to ribulose 5-phosphate, and resynthesis of the former from the latter. The stoichiometry of the pathway is ignored. 

State the different product stoichiometries obtained from the pentose phosphate pathway under conditions in which (1) more ribose 5-phosphate than NADPH is needed,... 

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