biochem mini 1b

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sweetlu
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biochem mini 1b
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2011-12-08 14:33:35
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biochem mini 1b
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biochem mini 1b
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  1. zero order rxn
    rate is INdependent on [S]
  2. first order rxn
    rate dependent on concentration of one substrate
  3. second order
    rate depends on contration of both substrates
  4. Alcohol dehyrogenase
    • -1.5 g/L saturation
    • - 10 g/hr limit
    • - not specific for EtOH, will use MeOH as well, which is why you can tx methanol poisoning with EtOH
  5. delta G
    • neg- spontaneous (exergonic)
    • pos- non-spontaneous (endergonic)
    • 0- rxn at eq
  6. Chemical changes catalyzed by AA side chains are limited to what
    • acid/base and nucleophilic/electrophilic changes
    • -coenzymes aid other reactions, ie redox
  7. classes of high energy biomolecules
    • High energy PO4 cpds (ATP,ADP etc)
    • reduced coenzymes (NADH, FADH2)
  8. resosance stability
    increase with the greater number of resonance referene structures
  9. ATP + H2O -----> ADP + Pi
    • -delta Go = -7.3 Cal/mol
    • -rxn requires Mg as cofactor
    • - same E released in ADP + H2O -----> AMP + Pi
  10. ATP + H2O -----> AMP + Pi
    delta G = -10.9 Cal/mol
  11. redox coez classes
    flavins- redox of C=C

    nicotinamides- redox of C=O by transferring H- (hydride ion), if H2 used an H+ will end up in solution producing acid
  12. absolute specificity
    • ez catalyzes one rxn for one S
    • ex. UREASE
  13. group specificity
    • ez catalyzed rxn involving only certain functional groups
    • ex. carboxypeptidase
  14. linkage specificity
    • ez catalyzes rxn for only a single bond type
    • ex. phosphotases
  15. k-1>>>k2
    means that ES is not perfect and it is more likely to break down to E + S than it is to go onto products (E+P)
  16. Vmax
    • = k2[E]
    • to increase rate: add more E or improve k2
  17. Km=[S]
    V0= Vmax/2
  18. [S]>>>Km
    V0=Vmax
  19. [S]<<<Km
    V0=Vmax/Km
  20. catalytic perfection
    every substrate that hits the enzyme causes a reaction

    kcat/Km = k1

    ex. ACh-esterase,CA, triose PO4-isomerase (glycolysis
  21. organophosphates
    • irreversible ACh-esterase inhibitor
    • -irreversible inhibitors form TRUE covalent bonds (often with ser residues) with the active site on an enzyme permanently inactivating it
    • "suicide inhibitors"
  22. allopurinol
    • irrevrsible XO inhibitor
    • xanthine----//----> urate
  23. nardil
    irreversible MAOI
  24. fomepizole
    • competitive inhibitor of AD
    • tx for MeOH poisoning
  25. Ki<<<Km
    means inhibitor affinity for enzyme will me much greater than S= good inhibitor
  26. competitive
    • competitive inhibition:
    • -Km increases
    • -Vmax unchanged
    • - increases S can overcome inhibition
    • -I competes with S for active site
    • -noncompetitive inhibition
    • -I binds at site OTHER than active site
    • - large amounts of S can NOT overcome inhibition
    • - Vmax decreases
    • -Km unchanged
  27. Rapid and reversible regulation of enzyme activity
    allosteric regulation and reversible covalent modification(ex. phosphorylation)
  28. allosteric enzymes
    • -composed of 2 or more protein chains, often regulatory site on one and active site on another
    • -can be upregulated or down regulated (A or I do not need to resemble S)
    • -catalyze irreversible rxn
    • -rate limiting
  29. heteroropic effectors
    • A and I that bind to allosteric sites
    • -are not identical to the substrate
  30. homotropic effectors
    • S acts as effector
    • -induces allosteric effects when it binds the active site
  31. lysozyme activity
    • digests bacteria cell wall by breaking BETA (1-4) GLYCOSIDIC BONDS between NAM and NAG
    • ** only effective against gram + bacteria**
  32. Serine protease family
    • ** all have a SER, HIS and ASP at their catalytic center, aka "catalytic triad"**
    • ** increased affinity with bulkyer side chain**
    • -his acts as buffer and grabs a H+ from serines OH group leaving an O-, which then attacks the peptide bond
    • -ex. chymotrypsin
  33. Metal ion catalysts
    • ** 1/3 of all known ez need a metal ion to work**
    • - metal either binds substrates to orient, redox, electrostatic stabilization or negative charge shielding
  34. end products of glycolysis
    anaerobic- lactic acid

    aerobic- pyruvic acid
  35. hemolytic anemia
    • can be caused by defect in any glycolysis enzyme
    • - G6PDH is most common
    • -recessive autosomal PK def is second (inc 2,3-BPG)
  36. aerobic oxidation of glucose
    • 3 NADH, 1 FADH2, 1GTP
    • NADH and FADH2 are used in the ETC
  37. gluconeogenesis substrates
    ala, pyruvate and lactic acid
  38. LDH
    • -resupplies NAD+ to G-3-PDH reaction
    • -pyruvate------> lactate
    • -under anaerobic conditions
  39. PFK-1
    • **main regulatory ez in glycolysis**
    • -irreversible(committing) and E consuming
    • - enhancer- *F2,6-BP(dec Km), AMP
    • -inhibitor-ATP-Mg
  40. metabolic Glu consumption
    • brain- 120 g/day
    • total- 160/day
  41. GK
    enzyme
    location
    reaction
    control
    • - specialized glucose specific HK w/ inc Km
    • -found in liver and pancrease
    • - irreversible, but not glycolysis committing Glu----> G6P (for glycogenolysis with GK)
    • - not inhibited by its product G6P, unlike other HK's
  42. pathways for G6P
    • - oxidation in glycolysis
    • - pentose PO4 p/w
    • - glycogenolysis
  43. G-3-PDH
    • **requires NAD+ (resuppled by LDH)**
    • - G3P----> 1,3 BPG
  44. arsenic
    inhibitor of substate level phosphorylation (used by PGK(7) and PK(10))
  45. 2,3 BPG
    enhances O2 release from RBC
  46. Fl-
    • potent inhibitor of enolase (8)
    • 2-PG ---//--> PEP
  47. Three irreversible reactions of glycolysis
    • HK (1)
    • PFK-1 (3)
    • PK (10)
  48. EtOH metabolism
    • - consumes NAD+
    • -can stop glycolysis and TCA
    • - can cause HYPOglycemia by stopping gluconeogenesis
    • -can cause acidosis by ketone metabolism
  49. NAD+/NADH + H redox state
    normal- 8/1

    alcoholic- 1/1
  50. regulatory enzymes in glycolysis
    HK, PFK-1, PK
  51. GK
    • regulator of glycolysis
    • - NO NEG. FEEDBACK BY G6P
    • -
  52. PK
    • regulator of glycolysis
    • -F1,6-BP will enhance and increase I:G
    • - ala and PO4 will inhibit
  53. increased insulin:glucagon
    • positively regulates PFK-1 and PK
    • inc I:G = low cAMP= low PKA activity= PFK-2 (unPO4)= PFK-2 kinase activity= increase F2,6-BP= increased PFK-1 activity= glycolysis stim for conversion on Glu to trigs
  54. PFK-2
    • synthesizes F2,6-BP (regulator of of PFK-1 in liver and adipose tissue)
    • -has a ser group that can be PO4ed
    • -PO4=PO4ase activity (in liver only)
    • -nonPO4= kinase activity (high I:G)
  55. glucagon and epi in liver
    inhibit glycolysis
  56. PFK-2 in cadiac muscle
    • PO4 increases PFK-2*KINASE* activity, because heart is a consumer organ as opposed to the liver that is a maintainer organ.
    • -so in the heart EPI increases glycolysis via increased cAMP cascade
  57. PK regulation
    • -ATP and ala inhibit
    • -F1,6-BP allosterically activates
    • -PO4 inactivates(only in liver form) via glucagon
    • -**no ser on the SkM and CM forms, so it is not inactivated by PO4 in these tissues**

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