Biochemical Foundations of Physiology -2 Part II

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Biochemical Foundations of Physiology -2 Part II
2014-09-01 01:10:15

Lecture 2-B
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  1. The conversion of glucose to pyruvate occurs in 2 phases , what are they ? What is the net amount ATP per glucose molecule ?
    Energy investment phase : phosphorylated forms of intermediates are synthesized at the expense of ATP.

    Energy generation phase : a net of 2 molecules of ATP are formed by substrate-level phosphorylation per glucose molecule metabolized.

  2. The irreversible phosphorylation of glucose by what enzymes allows for glucose to be trapped as the sugar as cytosolic glucose-6-phosphate (G-6-P)inside a cell ?
    • Hexokinase - muscles other cells 
    • Gluckokinase -Liver and Pancrease
  3. Hexokinase is inhibited by what molecule ?
  4. The isomerization of G-6-P to
    fructose-6-phosphate is catalyzed by ?
    phosphoglucose  isomerase
  5. The irreversible phosphorylation of F-6-P to
    Fructose-1,6-bisphosphate is catalyzed by ?  

    Why is This reaction is the most important control point and rate limiting and
    committed step of glycolysis ? (regulatory point #2)
    phosphofructokinase-1 (PFK-1)

    It is irreversible
  6. Fructose-1,6-bisphosphate is cleaved to dihydroxyacetone phosphate and
    glyceraldehyde-3-phosphate by what enzyme ?
  7. What catalyzes the interconversion of DHAP and G-3-P so that it can be used in the next ?step. DHAP must be isomerized to G-3-P for furthermetabolism by the glycolytic pathway
    Triose phosphate isomerase

    Yields two G-3-P's
  8. G-3-P is oxidized to
    1,3-bisphosphoglycerate by what enzyme ?During this step  the NADH formed by this reaction must be reoxidized back to NAD+ for glycolysis to continue.
    Glyceraldehyde 3-phosphate dehydrogenase
  9. What are the 2 major mechanisms for oxidizing NADH ?
    1)The NADH linked conversion of pyruvate to lactate (anaerobic)

    2)  Oxidation of NADH via the respiratory chain (aerobic)
  10. 1,3-bisphosphoglycerate (1,3-BPG) is converted to 3-phosphoglycertae by the enzyme ? 

    In this reaction thehigh energy phosphate
    group of 1,3-BPG is used to synthesize ATP from ADP
    phosphoglycerate kinase
  11. 3-phosphoglycerate is converted to 2-phosphoglycertae by what enzyme ?
    phosphoglycerate mutase
  12. 2-phosphoglycerate is dehydrated to phosphoenolpyruvate (PEP) by what enzyme ?

    What can inhibit this enzyme ?

  13. Phosphoenolpyruvate (PEP) is converted
    to pyruvate by what enzyme ?

    This is the third irreversible reaction of glycolysis (regulatory point #3)
    Pyruvate kinase
  14. What does the fate of pyruvate depend on ?
    celltype and the availability of oxygen
  15. What are the fates of pyruvate ?
  16. What is the Net yield for Glycolysis ?
    2 pyruvate + 2NADH + 2 ATP (Net)