Gluconeogenesis and Pentose Phosphate Pathway

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pebbles135
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46018
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Gluconeogenesis and Pentose Phosphate Pathway
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2010-10-30 21:44:14
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Biochemblock3
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Biochem block3 Lecture 28 Chapter 8
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  1. How many and what are the common enzymes used between glycolysis and gluconeogenesis?
    7: Phosphoglucose Isomerase; Aldolase; Triose Phosphate Isomerase; Glyceraldehyde-3-Phosphate Dehydrogenase; Phosphoglycerate Kinase, Phosphoglycerate Mutase; Enolase
  2. Identify the enzymes that are unique to gluconeogenesis
    • Pyruvate carboxylase
    • PEP carboxykinase
    • Fructose-1,6-bP
    • Glucose-6-phosphatase
  3. What are the txtbook substrates of gluconeogenesis?
    • Lactate via the Cori Cycle
    • Glycerol via conversion to DHAP
    • Alanine via conversion to pyruvate
  4. Identify the substrates of gluconeogenesis
    • 4 ATP
    • 2 GTP
    • 2 NADH
    • ?
  5. Identify the regulation points of gluconeogenesis
    • Synthesis of PEP
    • Conversion of fructose-1,6-bisphosphate to fructose-6-phosphate
    • Formation of glucose from glucose-6-phosphate
  6. Define gluconeogenesis
    The process is generally the reverse of glycolysis with the exception of three key steps
  7. Define the Pentose Phosphate Pathway
    Refers to metabolism of glucose that does not generate ATP but is used to form several important molecules used in other processes
  8. What can cells in the liver use to make glucose?
    lactate, pyruvate, glycerol, and certain a-keto acids
  9. What other organ besides the liver can make glucose?
    Kidneys can make a small amount of glucose
  10. When is gluconeogensis only used?
    When glycogen is depleted from the liver which can be caused by intesnse exercise or prolonged fasting
  11. What depends on glucose for energy?
    Brain and rbc's
  12. What are the enzyme(s) required for the synthesis of PEP?
    • Pyruvate carboxylase
    • PEP carboxykinase
  13. What is the function of Pyruvate carboxylase and where does the rxn take place?
    In the mitochondria converts pyruvate to oxaloacetate (OAA) by the addition of CO2
  14. What is the function of PEP carboxykinase?
    Converts OAA to PEP
  15. Gluconeogenesis is generally the reverse of glycolysis with the exception of three key steps:
    Hexokinase, PFK-1, and pyruvate kinase
  16. Which enzyme requires the coenzyme biotin?
    Pyruvate carboxylase
  17. During gluconeogenesis regulation, what activates and inhibits pyruvate carboxylase?
    • Activates: Acetyl-CoA
    • Inhibits: Nothing on pic
  18. During gluconeogenesis regulation, what activates and inhibits Fructose-1,6-bisphosphatase?
    • Activates: ATP; citrate
    • Inhibits: Fructose-2,6-bisphosphate, AMP
  19. During glycolysis regulation, what activates and inhibits Hexokinase?
    • Activates: Nothing on pic
    • Inhibits: Glucose-6-phosphate
  20. During glycolysis regulation, what activates and inhibits Phosphofructokinase?
    • Activates: Fructose-2,6-bP; AMP
    • Inhibits: ATP, citrate
  21. During glycolysis regulation, what activates and inhibits Pyruvate Kinase?
    • Activates: Nothing on pic
    • Inhibits: ATP; Fructose-1,6-bP; Acetyl-CA; cAMP-dependent phosphorylation
  22. What are 3 key products of Pentose Phosphate Pathway?
    • Ribose-5-phosphate-makes ribonulceotides
    • Fructose-6-phosphate
    • Glyceraldehyde-3-phosphate
  23. When does the Pentose Phosphate Pathway generate 2 molecules of NADPH?
    Oxidative phase
  24. What are the two phases of pentose phosphate pathway?
    Oxidative and Nonoxidative
  25. What is produced from the Oxidative Phase of Pentose Phosphate Pathway?
    • Glucose-6-phosphate is used and proceeds through three enzyme-catalyzed reactions to form D-ribulose-5-phosphate
    • 2NADH
  26. Where is the oxidative phase active?
    adipose tissue, red blood cells, and certain other tissues
  27. What is the important of NADPH molecules?
    Key antioxidants and are needed during lipid synthesis
  28. What is produced during the nonoxidative phase?
    Ribose-5-phosphate
  29. How is Ribose-5-phosphate formed?
    Ribulose-5-phosphate from oxidative phase is converted to ribose-5-phosphate
  30. What can be made during the nonoxidative phase from Ribulose-5-phosphate (oxidative) when cells don't need pentose phosphates (ribose)?
    Cells use the other reactions of this phase to form glycolytic intermediates (F6P, GAP)
  31. Are the rxns during the oxidative phase reversible or irreversible?
    irreversible
  32. Are the rxns during the nonoxidative phase reversible or irreversible?
    reversible
  33. Where is the pentose phosphate pathway located?
    cytoplasm

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