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BMSC 200 > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

vitalism

A

belief that living things are different from non-living

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2
Q

protease

A

pre-digest proteins

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3
Q

lipase

A

together with protease, break down substances into smaller water soluble substances

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4
Q

carbohydrase

A

convert starch syrup to sugar syrup

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5
Q

isomerase

A

convert glucose to fructose (sweeter)

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6
Q

co-factors

A

inorganic ions required by some enzymes for activity

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7
Q

co-enzymes

A

vitamins required by some enzymes for activity

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8
Q

prosthetic group

A

tightly associated with enzyme (like glued)

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9
Q

apoenzyme

A

lack of extra factor

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10
Q

holoenzyme

A

apoenzyme with extra factor

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11
Q

6 classifications of enzymes

A
  • oxidoreductases
  • transferases
  • hydrolases
  • lyases
  • isomerases
  • ligases
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12
Q

chemical catalysts…

A

require extremes of temp, pressure, pH

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13
Q

enzymes function at…

A

physiological conditions

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14
Q

enzymes have a ________.

A

high degree of specificity

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15
Q

Active sites can change…

A

pKa

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16
Q

Substrates are bound to enzymes by…

A

weak interactions (H bonding, electrostatic, hydrophobic, vdW)

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17
Q

specificity of substrate depends on….

A

arrangement of atoms in the active site

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18
Q

substrate binding can cause…

A

induced fit or conformation selection

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19
Q

hand

A

substrate

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20
Q

glove

A

enzyme

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21
Q

P < S

A

spontaneous

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22
Q

binding effects

A

interaction between enzyme and substrate

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23
Q

chemical effects

A

accepting/donating protons; forming covalent linkages

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24
Q

Induced fit during E+S causes…

A

active site to become more complimentary toward transition state

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25
Q

Substrate binding promotes reaction by…

A
  • reducing entropy
  • removal of water molecules to expose reactive groups
  • alignment of reactive functional groups of enzyme with substrate
  • distortion of substrates
  • induced fit as a response
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26
Q

Increased interactions of enzyme and substrate occurs in….

A

transition state

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27
Q

enzymes have higher affinity for ….

A

transition state than substrates

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28
Q

transition state analogs

A

stable compounds whose structures resemble unstable transition states

29
Q

catalytic antibodies

A
  • abzymes
  • generated against a transition state analog may bind to substrate, catalyzing rex by promoting formation of transition state
30
Q

What participates in enzymatic catalysis?

A
  • polar, ionizable residues (Asp, Glu, His, Cys, Tyr, Lys, Arg, Ser)
  • anions and cations of certain amino acids
31
Q

two commonly observed mechanisms of catalysis

A
  • acid/base

- covalent

32
Q

for most enzymes, greatest activity at…

A

physiological pH 7.4 and 37 degrees

33
Q

steady state equation

A

rate of formation of ES complex is equal ti rate of its breakdown

34
Q

Km

A

amount of substrate required for enzyme to function at half maximal velocity

35
Q

[S] < Km

A

enzymes are highly sensitive to change in substrate conc., but have very little activity

36
Q

[S] > Km

A

enzymes have high activity but are insensitive to changes in substrate concentration.

37
Q

[S] = Km

A

enzyme has significant activity and is responsive to changes in substrate concentration

38
Q

kcat

A

-enzyme turnover number

the number of molecules of substrate converted to product per unit time by a single enzyme

39
Q

how to calculate kcat

A

Vmax/[E]t

40
Q

reversible enzyme inhibitors

A

bind to enzyme by non-covalent interactions

  • competitive
  • uncompetitive
  • non-competitive
41
Q

competitive inhibitors

A

resemble substrate

  • binds only to enzyme
  • increase Km
42
Q

uncompetitive

A
  • bind to ES

- decrease Vmax and Km

43
Q

non-competitive

A
  • bind to E and ES

- decrease Vmax

44
Q

irreversible enzyme inhibitors

A
  • highly stable covalent bonds with enzymes

- permanently inactivates enzyme

45
Q

what are serine protease

A
  • digestive enzyme
  • mediate turnover of self proteins
  • in pancreas as inactive zymogens
  • both covalent and acid/base catalysis
46
Q

zymogens

A

prevent damage to cellular proteins, activated by selective proteolysis

47
Q

trypsin cleaves

A

Lys and Arg

48
Q

chymotrypsin cleaves

A

Phe, Tyr

49
Q

Elastase cleaves

A

Gly, Ala

50
Q

papain

A

cuts all peptide bonds

51
Q

catalytic triad

A

His, Asp, Ser

52
Q

catalytic triad - His

A

removes H from Ser hydroxyl to make it a strong nucleophile and donate electrons and activating a water molecule to regenerate the free enzyme – acid/case catalysis

53
Q

catalytic triad - Asp

A

stabilize the positively-charged His to facilitate serine ionization

54
Q

catalytic triad - Ser

A

acts as nucleophile (tendency to donate e-) attaching the carbonyl grouop of the polypeptide substrate – covalent catalysis

55
Q

enzyme can be regulated by:

A
  • controlling amount present (long term)

- adjusting activity of a constant quantity (short term)

56
Q

enzymatic pathways often controlled through

A

negative feedback by final product

57
Q

final product often inhibits…

A

first step; conserving material and energy and prevent accumulation of intermediates

58
Q

negative feedback is…

A

a branched pathway

59
Q

allosteric enzymes do not….

A

obey michaelis-mentin kinetics and have signoidal curves

60
Q

allosteric enzyme binding of substrate disrupts R to T equilibrium in favour of…

A

R

61
Q

cooperatively/threshold effect

A

Allosteric enzymes transition from a less active state to a more active state within a narrow range of substrate concentration. They are sensitive near the Km than M-M enzymes of the same Vmax. Below this sensitivity there is little zctivity, after the threshold, the enzyme activity rapidly increases.

62
Q

PEP is an ____________ of PFK-1

A

allosteric inhibitor

63
Q

ADP is an _________ of PFK-1

A

allosteric activator

64
Q

When ration of [PEP]/[ADP] is low….

A

PFK is activated and glycolysis produces more ATP

65
Q

glycogen synthase

A

-anabolic, catalyzes production of glycogen from glucose

66
Q

glycogen phosphorylase

A

-catabolic, catalyze breakdown of glycogen into glucose

67
Q

phosphorylation favours….

A

breakdown of glycogen into glucose in response to glucagon and epinephrine (anabolic inactive)

68
Q

dephospho rylation favours….

A

storage of glucose as glycogen in response to insulin (catabolic inactive)

BMSC 200 (11 decks)

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