Pentose, Galactose and Fructose

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Pentose, Galactose and Fructose
2011-09-24 00:40:33
Pentose pathway galactose breakdown fructose

Pentose p/w and breakdown of galactose and fructose
Show Answers:

  1. What are the 2 parts of the Pentose pathway?
    • Oxidative Phase: Get NADPH
    • Non-Oxidative Phase: Reshuffling
  2. What is Ribose-5-P used for?
    • ATP
    • DNA/RNA
    • FAD/NAD
    • CoA
  3. What reactions/enzymes form NAPDH?
    • G6P --> 6-Phosphoglucanolactone (G6P DH)
    • 6-Phophogluconate --> Rubulose-5-Phosphate (6-phosphogluconate DH)
  4. What occurs due to a deficiency in G6P DH?
    • Low NAPDH concentration
    • Manifested in RBC
    • Hemolytic anemia
  5. What is NAPDH directly used for in RBCs?
    To reduce glutathione and allow the breakdown of H2O2 to H2O
  6. Where do the molecules of the pentose pathway re-enter glycolysis?
    • F6P
    • GAP
  7. What enzyme's activity is measured in order to determine thiamine deficiency?
  8. If only NADPH is needed, how does the pentose pathway proceed?
    • Oxidative reactions to make NADPH
    • Nonoxidative reactions to make F6P and GAP
    • THEN, these are remade into G6P to redo again
  9. If NADPH and ribose-5-P are needed, how does the pentose pathway proceed?
    • Oxidative reactions make NADPH and ribulose-5-P
    • Ribulose 5-P is converted to ribose-5-P
  10. If only ribose-5-P is needed, how does the pentose pathway proceed?
    Nonoxidative reactions only - in reverse
  11. What inhibits G-6-P dehydrogenase?
    High NAPDH
  12. If NADPH and pyruvate are needed, how does the pentose pathway proceed?
    • Normally through oxidative and non-oxidative
    • Then continues through glycolysis upon formation of F6P and GAP
  13. What is the structure of sucrose?
    Glucose (alpha 1,2) Frucose
  14. What is the structure of lactose?
    Galactose (beta 1,4) Glucose
  15. What enzyme function is seen in frucose, galactose and glucose metabolism?
    An initial kinase that sequesters the molecule in the cell
  16. Where do the products of frucose matabolism enter glycolysis?
    • DHAP
    • GAP
  17. What transporter is used to transport fructose into the liver?
  18. Describe fructosuria:
    • Deficiency: Fructokinase
    • Benign, asymptomatic
    • 90% is eventually metabolized
  19. Describe fructose intolerance:
    • Deficiency: Aldolase B
    • Build up of F-1-P
    • Inhibits gluconeogenesis and glycogenolysis
    • Causes: Hypoglycemia and lactic acidosis
  20. What is lactose made of in the mammary gland and using what enzyme?
    • Glucose + UDP-Galactose
    • Enzyme: Lactose synthase
  21. What are the final products of galactose metabolism and where do they go?
    • Glucose-6-P --> glycolysis
    • Glucose --> other tissues
  22. How is glucose formed from glucose-6-P in the metabolism of galactose?
  23. Describe non classical galactosemia
    • Deficiency: Galactokinase
    • Causes: Build up of galactose
    • Result: Formation of cataracs due to build up of galactitol
  24. Describe classical galactosemia:
    • Deficiency: Galactose-1-P Uridylyltransferase
    • Causes: Accumulation of galactose-1-P
    • Result: Severe neurological effects and liver damage
  25. What 2 enzymes do the reshuffling during nonoxidative phase of the pentose pathway?
    • Transketolase
    • Transaldolase
  26. What cofactor is used during the non-oxidative phase and by who?
    • TPP
    • By transketolase