Biochem final

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Biochem final
2010-08-04 00:36:05

TCA cycle, enzyme inhibition / activation, membrane transport
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  1. acetylCoA + OAA --> citrate

    • citrate synthase enzyme
    • nucleophilic attack on OAA
    • citrate --> isocitrate
    • enzyme: acotinase, forces chirality
    • dehydration followed by hydration rxn (intermediates left out)
    • cant oxidize citrate its a 3o alcohol, isocitrate is a 2o alcohol that can be oxidized.
    • isocitrate --> a-ketoglutarate
    • enzyme: isocitrate dehydrogenase
    • first of 4 oxidation reactions
    • creates first NADH of the cycle
    • the last COO- from isocitrate (under the grp that came from AcetylCoA) leaves as CO2
    • a-kg --> succinylCoA
    • enzyme: a-kg dehydrogenase: same as pyruvate dehydrogenase, does everything the same, TPP nucleophilic attack, LIP, CoA
    • its the 2nd oxidation rxn (oxidative decarboxylation)
    • TPP attacks 2nd Co of a-kg and the first COO- grp leaves as CO2
    • makes FADH2 and NADH
    • 1st step in SuccinylCoA --> Succinate
    • added a pi group to succinylCoA
    • enzyme: succinate synthetase
    • phosphorylation is NOT an oxidation rxn
    • Last intermediate step in succinylCoA --> Succinate
    • pi grp removal makes GDP-->GTP
    • enzyme: succinate synthetase
    • 1st step in Succinate --> OAA
    • enzyme: succinate dehydrogenase
    • makes FAD --> FADH2
    • so this is an oxidation
    • last step in Succinate --> OAA
    • enzyme: succinate dehydrogenase
    • OH grp gets oxidized, making NAD+ --> NADH
    • *remember* succinate dehydrogenase is complex II in the e- transport chain
  2. Ways to inhibit Pyruvate Dehydrogenase
    • high [conc] of ATP, binds allosterically @ I so TPP cant attack pyruvate, easily reversilble
    • high [NADH] / low [NAD+]: when NADH and ATP is high energy needs have been met
    • phosphorylation by a kinase: high [conc] of ATP and NADH promote phosphorylation:
    • adds a pi group to complex I - creates repulsion (p groups are negative) and changes shape of PDH
    • covalent bond, not easily reversed. phosphatase must remove the p group
    • ATP binds to Ca2+ / Mg2+ and prevents activation enzyme phosphatase from being activated
  3. Ways activate Pyruate Dehydrogenase
    • low [ATP]: results in free Ca2+ / Mg2+ and low [ATP] means wont bind to inhibition site
    • Phosphatase enzyme: removes pi grp, needs high [Ca / Mg]
    • high [ADP] and [pyruvate] inhibit kinase, allows PDH to keep going
  4. inhibitors and activators for phosphofructo kinase
    • ATP: inhibitor, allosteric
    • AMP: activator, allosteric but larger K than ATP
    • fructose 2,6-biphosphate is an allosteric activator
  5. Membranes: saturated
    • all single bonds
    • can twist around each other better
    • higher melting temp
  6. membranes: unsaturated
    • has a c=c double bond
    • tails more rigid than saturated
    • lower melting temps

    remember: shorter chains also means lower melting temp
  7. delta G for uncharged species
    • deltaG = RT ln [to] [from]
    • remember deltaG is favorable (-) when you move from [high] to [low]
  8. deltaG for charges species
    • deltaG = RT ln [to]/[from] - NFEo
    • N = charge
    • F = 96,500 J/V
    • E = (+) or (-) .07V depends on where ur going: (+) if ur going towards ur opposite charge, (-) if your going from to ur same charge (repulsion, yuck)
    • *remember* outside of membrane is (+), inside of membrane is (-)