Chapter 17 Lecture 2

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  1. WHat does the CAC do? 

    What is it? 

    Where do the reactions take place?
    oxidizes acetly groups from carbs, fatty acids, and amino acids

    cycle (like one big enzyme)

    all reactions in the mitochondria
  2. What does the CAC do to carbons? 

    Building blocks? 

    Short summary
    2 C in, 2 C out each cycle

    intermediates are the building blocks

    acetyl --> CO2, transfer 4 pair of electrons to 3 NADH and 1 FADH2, get 1 GTP
  3. Step 1
    oxaloacetate+ acetyl coA--> citrate

    catalyzed by citrate synthase (induced fit enzyme)

    forms a 6 carbon structure that is needed to start the cycle
  4. What is the structure of citrate synthase?
    two active sites; two conformations

    we don't want acetyl CoA to come in and have them hydrolyzed off. The enzyme helps this by remaining inactive until oxaloacetate binds; the active site closes. Acetyl CoA binds and 2 substrates are in the active site forming the substrate complex
  5. From the substrate complex, an __ forms, and it is __. 

    In the citryl CoA complex, what happens?
    • enol intermediate
    • highly reactive and can allow condensation  to take place

    at this point, a 2nd conformation change takes place--> bond broken between citrate CoA
  6. citrate--??--> isocitrate
    aconitase: via intermediate, you remove water, add water, etc.
  7. In aconitase, what is involved?
    iron is involved; in iron cluster: mutliple iron atoms cluster with sulfurs--> helps facilitate a reaction

    4 Fe 4S cluster
  8. In the step with isocitrate dehydrogenase, what happens?
    • NADH forms
    • isocitrate--> alpha ketoglutarate

    it catalyzes oxidative decarboxylation
  9. What is favorable with isocitrate dehydrogenase?
    oxidation is favorable/ decarboxylation is not so much, coupling addition of O2 with removal of CO2
  10. Alpha-ketoglutarate dehydrogenase complex
    enzyme complex catalyzes this (a thioester bond) 

    electrons captured in NADH

    this is teh 2nd oxidative decarboxylation
  11. Succinyl CoA--> succinate

    Where does the energy come from?
    succinyl-CoA synthetase

    takes phosphate and GDP to become GTP

    the energy comes in and energy from attaching succinate to CoA will supply nergy
  12. An enzyme called __ can take GTP and ADP--> GDP and ATP
  13. nucleoside diphosphate kinase
  14. Explane succinate dehydrogenase
    associated with the inner mitochondrial membrane and tghtly linked to ETC

    • remove electrons
    • --> energy not sufficient to form NADH--> so, FADH2 forms
  15. Fumarase
    adds water to convert Fumarate to malate
  16. malate
    has enough electron transfer potential to form NADH
  17. Final step of the pathway
    Malate back to oxaloacetate by malate dehydrogenase
  18. What was an experiment to identify if the same oxaloacetate is used?
    They radioactively labeled terminal carbon on oxaloacetate. THough the molecule was symmetrical, the carbon that gets removed is the oxaloacetate one. 

    The reason for this is because, though it is symmetric, the enzyme is not and binds in a certain way that causes exposure of the carboxyl end of oxaloacetate, whch gets removed
  19. What is the problem with oxaloacetate?
    it is a building block of aspartic acid, asparagine, lysine, isoleucine, methionine, and threonine

    So, it gets removed from the CAC. To restore the amounts that left, pyruvate gets converted to it by pyruvate carboxylase
  20. alpha-ketoglutarate?
    gets converted to glutamate and then other amino acids and purines

    intermediate that can be removed to make several amino acids
  21. Succinyl CoA
    can be converted to porphyrins, heme, chlorophyll
  22. Porphyrins require?
    2 succinyl CoA
Card Set
Chapter 17 Lecture 2
Test Four
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