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The pentose phosphate pathway

The pentose phosphate pathway. Important for both biosynthesis and catabolism Can operate at the same time as glycolysis Can operate aerobically or anaerobically. The pentose phosphate pathway. Begins with oxidation of glucose-6-phosphate to 6-phosphogluconate

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The pentose phosphate pathway

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  1. The pentose phosphate pathway Important for both biosynthesis and catabolism Can operate at the same time as glycolysis Can operate aerobically or anaerobically

  2. The pentose phosphate pathway Begins with oxidation of glucose-6-phosphate to 6-phosphogluconate 6-phosphogluconate is then oxidized to ribulose-5-phosphate and CO2 Yields 2 molecules of NADPH

  3. The pentose phosphate pathway Ribulose-5-phosphate converted to ribose-5-P and xylulose-5-P Transketolase converts sugars to glyceraldehyde-3-P and sedoheptulose-7-P Transaldolase converts sugars to fructose-6-P and erythrose-4-P

  4. The pentose phosphate pathway Ribulose-5-phosphate converted to ribose-5-P and xylulose-5-P Transketolase converts sugars to glyceraldehyde-3-P and sedoheptulose-7-P Transaldolase converts sugars to fructose-6-P and erythrose-4-P

  5. The pentose phosphate pathway Erythrose-4-P and xylulose-5-P converted to fructose-6-P and glyceraldehyde-3-P by transketolase Glyceraldehyde can be combined with dihydroxyacetone phosphate to form fructose-6-phosphate

  6. Roles of the pentose phosphate pathway Production of NADPH for the reduction of molecules in biosynthesis Synthesis of 4 and 5 carbon sugars required for various purposes Synthesis of 6 carbon sugars (hexoses) from 5 carbon sugars (pentoses)

  7. Roles of the pentose phosphate pathway Production of ATP from intermediates Glyceraldehyde-3-P Pyruvate NADPH  NADH Catabolism of pentoses

  8. The Entner-Doudoroff pathway Like glycolysis, can be used for the catabolism of hexoses Glucose-6-P converted to 6-phosphogluconate Generates 1 NADPH

  9. The Entner-Doudoroff pathway 6-phosphogluconate dehydrated to form 2-keto-3-deoxy-6-phosphogluconate (KDPG) KDPG split in two to form pyruvate and glyceraldehyde-3-P Glyceraldehyde converted to pyruvate (same enzymes as glycolysis)

  10. The Entner-Doudoroff pathway 1 glucose = 1 ATP + 1 NADPH + 1 NADH Some microorganisms substitute the E-D pathway for glycolysis Normally only found in gram-negatives (Pseudomonas, Rhizobium, Azotobacter, Agrobacterium)

  11. Fermentations NADH must be oxidized to NAD+ in order to oxidize glyceraldehyde-3-P In the absence of an electron transport chain pyruvate or a derivative serves as the electron acceptor for NADH Can lead to the production of some ATP

  12. Commonalities of fermentations NADH is oxidized to NAD+ The electron acceptor is often pyruvate or a pyruvate derivative The substrate is partially oxidized

  13. Commonalities of fermentations ATP is produced by substrate-level phosphorylation Oxygen is not needed

  14. Fermentations Different fermentations are often characteristic of particular microbial groups

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