High energy phosphates are not produced in
A. HMP shunt
B. Oxidative pathway
C. TCA
D. Glycolysis
Ans. A. (HMP shunt)
Explanation
.•“Hexose Monophosphate Shunt Pathway (HMP) produces NADPH that is required for several synthetic pathways, e.g., for fatty acids and steroid synthesis. However, the NADPH produced is not converted to ATP or used for energy production (unlike NADH produced in glycolysis and TCA cycle)” — Devlin and Rama Rao
• The HMP shunt or pentose phosphate pathway serves several purposes, including synthesis and degradation of sugars other than hexoses, particularly pentoses is necessary for synthesis of nucleotides and other glycolytic intermediates.
• Most important is the ability to synthesize NADPH, which has a unique role in biosynthetic reactions.
• The direction of flow and path taken by G6P after entry into the pathway is determined largely by the needs of the cell for NADPH or sugar intermediates.
• When more NADPH than ribose 5-phosphate is required, the pathway leads to complete oxidation of G6P to CO2 and resynthesis of G6P from ribulose 5-phosphate.
•Alternatively, if more ribose 5-phosphate than NADPH is required, G6P is converted to fructose 6-phosphate and glyceraldehyde 3-phosphate by the glycolytic pathway.
•The distribution of the pentose phosphate pathway in tissues is consistent with its functions. It is present in erythrocytes for production NADPH, required to generate reduced glutathione, which is essential for maintenance of normal red cell structure.
• It is also active in liver, mammary gland, testis, and adrenal cortex, sites of fatty acid or steroid synthesis that also require the reducing power of NADPH.
High energy phosphates are not produced in
A. HMP shunt
B. Oxidative pathway
C. TCA
D. Glycolysis
Ans. A. (HMP shunt)
Explanation
.•“Hexose Monophosphate Shunt Pathway (HMP) produces NADPH that is required for several synthetic pathways, e.g., for fatty acids and steroid synthesis. However, the NADPH produced is not converted to ATP or used for energy production (unlike NADH produced in glycolysis and TCA cycle)” — Devlin and Rama Rao
• The HMP shunt or pentose phosphate pathway serves several purposes, including synthesis and degradation of sugars other than hexoses, particularly pentoses is necessary for synthesis of nucleotides and other glycolytic intermediates.
• Most important is the ability to synthesize NADPH, which has a unique role in biosynthetic reactions.
• The direction of flow and path taken by G6P after entry into the pathway is determined largely by the needs of the cell for NADPH or sugar intermediates.
• When more NADPH than ribose 5-phosphate is required, the pathway leads to complete oxidation of G6P to CO2 and resynthesis of G6P from ribulose 5-phosphate.
•Alternatively, if more ribose 5-phosphate than NADPH is required, G6P is converted to fructose 6-phosphate and glyceraldehyde 3-phosphate by the glycolytic pathway.
•The distribution of the pentose phosphate pathway in tissues is consistent with its functions. It is present in erythrocytes for production NADPH, required to generate reduced glutathione, which is essential for maintenance of normal red cell structure.
• It is also active in liver, mammary gland, testis, and adrenal cortex, sites of fatty acid or steroid synthesis that also require the reducing power of NADPH.
