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BMSC 200 > Chap 6 > Flashcards

Chap 6 Flashcards

1
Q

enzyme function

A

provide mechanism for acceleration,regulation, and coordination of chemical reactions

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2
Q

enzyme contribute to human health as

A

causes of diseases;
therapeutic targets;
indicators of disease

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3
Q

enzyme as causes of diseases

A

gain, loss or change of function of ana enzyme can have pathological consequences

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4
Q

enzyme as therapeutic targets

A

many therapeutic drugs target activity of specific enzymes

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5
Q

enzyme as indicators of disease

A

biomarkers to inform disease susceptibility,prognosis and treatment

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6
Q

enzymes are all ___except for a small group of __

A

proteins;

catalytic RNA molecules

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7
Q

some enzyme’s protein component is fully __,others need___or ___for activity

A

active;
co-factors;
co-enzymes

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8
Q

prosthetic group

A

a co-enzyme or co-factor that is tightly associated with the enzyme

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9
Q

catalysts functions

A

lower the amount of energy required for a reaction to proceed;
speed up attainment of equilibrium but do not change equilibrium;
are unchanged by the reaction, recycled to participate in another reaction

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10
Q

Circe effect

A

some enzyme are able to catalyze reaction faster than predicted by diffusion-control limits

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11
Q

enzyme work by___

A

catalyze the inter-conversion of substrate and product ;

E+S<>ES<>E+P

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12
Q

substrate

A

molecule to be acted upon by the enzyme

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13
Q

product

A

what is produced by the enzyme

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14
Q

active site

A

the portion of the enzyme responsible for binding the substrate leading to the formation of an enzyme-substrate complex

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15
Q

structurally: active site is ____ formed from groups that come from ____. It takes up ____of the enzyme

A

a 3D cleft;
different parts of the polypeptide chain;
a small part of the total volume

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16
Q

reaction: active sites are _______, water is usually _____ the active site.

A

unique microenvironments;

excluded from

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17
Q

reaction: substrates are bound to enzyme by _____.

A

multiple weak interactions

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18
Q

structure: specificity of substrate binding depends on the _____ the active site; substrate binding can cause ___ or _____.

A

precisely defined arrangement of atoms in;
induced fit;
conformation selection

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19
Q

how enzyme work: by influencing ___ but not _____, therefore, didn’t influence the ____.

A 
activation energy (delta G++);
free energy (delta G);
equilibrium of the reaction
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20
Q

the delta G of a reaction depends only on the ___ ( ) the ____. the delta G of a reaction is independent of the _____.

A

free energy of the product;
minus;
free energy of the reactants;
steps of the transformation

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21
Q

the delta G provides no information about ______.

A

rate of a reaction

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22
Q 
enzyme catalytic capabilities result from chemical effects 
1.\_\_\_\_
2.\_\_\_\_
and binding properties
1.\_\_\_\_\_
2.\_\_\_\_\_
A

acid/base catalysis;
covalent catalysis;
substrate binding;
transition-state stabilization;

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23
Q

binding effects: binding of reactants in enzyme active sites provides ___ and ___

A

substrate specificity;

catalytic power

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24
Q

substrate binding: enzyme properly __ and __ substrates, makes the formation of the transition state more __ and ___.

A

gather; position;

frequent; lowers the energy of activation

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25
Q

substrate binding promotes reactions by

A
  1. reducing entropy
  2. removal of water molecules to expose reactive groups;
  3. alignment of reactive functional groups of the enzyme with the substrate
  4. distortion of substrates
  5. induced fit of the enzyme in response to substrate binding
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26
Q

transition-state (TS) stabilization: the essence of catalysis is stabilization of __. enzyme bind to transition state __ than substrates

A

transition state;

much more tightly

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27
Q

transition-state analogs (TSAs) are _.

A

stable compounds whose structures resemble unstable transition states

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28
Q

TSA application as therapeutics

A
  1. competitive inhibitors

2. generation of catalytic antibodies

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29
Q

competitive inhibitors

A

bind the active site of a target enzyme active site with high affinity, preventing substrate binding

30
Q

catalytic antibodies (Abzymes)

A

antibodies generated against a TSA may also bind the substrate, catalyzing the reaction by promoting formation of the transition state

31
Q

chemical effects often involve

A
  1. polar, ionizable residues at the active site

2. anions and cations of certain a.a.

32
Q

acid-base catalysis: achieved by catalytic transfer of __. ___, with a pKa near ___, is often involved in acid/base catalysis.

A

a proton;
histidine
physiological pH

33
Q

covalent catalysis: involve __ steps ( ); an example will be___.

A

2;

  1. forms a covalent linkage to the enzyme;
  2. regenerate the free enzyme;
    eg. glucose-fructose+Pi<=>fructose+glucose-P
34
Q

enzyme kinetics definition:___ ;

equation:____

A

study of the rates at which reactions occur;

V= delta [P]/ delta t

35
Q

variables influence reaction rates:

A

T, pH (affects all protein)
enzyme concentration
substrate concentration

36
Q

initial velocity (Vo):

A

velocity at the beginning of an enzyme catalyzed reaction, prior to product accumulation

37
Q

initial velocity equation

A

Vo= [ES] k2

k2: rate constant of formation of product from ES

38
Q

Michaelis-Menten eqution

A

Vo = Vmax [S]

Km + [S]

39
Q

Km represents

A

[S] required to reach 1/2 Vmax

40
Q

Vmax represents

A

maximum velocity of the enzyme

41
Q

when [S] < Km,

A

enzymes are highly sensitive to changes in substrate concentration but have very little activity

42
Q

when [S] > Km

A

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

43
Q

when [S] =Km

A

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

44
Q

Lineweaver-Burke plot equation:__

, it is used to determine___

A

1/Vo = Km/Vmax[S] + 1/Vmax;

Vmax and Km

45
Q

in the lineweaver-Burke plot, the slope= __, x-intercept = __, y-intercept = ___.

A

Km/Vmax;
(-)1/Km;
1/Vmax

46
Q

enzyme turnover number (aka, __) _________, calculated by ___.

A

Kcat;
equals the number of molecules of substrate converted to product per unit time under saturating conditions;
Vmax / [Et]

47
Q

inhibitors can prevent formation of __ or the ___.

A

ES;

breakdown to E and P

48
Q

reversible inhibitors bind to the enzyme by ____; we will consider these classes of it: ____

A

non-covalent interactions;
competitive;
uncompetitive;
noncompetitive

49
Q

competitive inhibitor___, they bind to ___ not ___;

Vmax ___ and Km____

A 
resemble the substrate;
free enzyme only;
ES;
be same ;
increases
50
Q

uncompetitive inhibitors bind to __; Vmax ___ and Km ___.

A

ES complex only;
decreases by conversion of ES to ESI;
also decreases

51
Q

noncompetitive inhibitor bind to ___; Vmax __ and Km ___.

A

both E and ES;
decreases;
doesn’t change

52
Q

irreversible enzyme inhibitors form ___ with the enzyme; ___ the enzyme; useful for study ____.

A

stable interactions or covalent bonds;
permanently inactivate;
reaction mechanisms

53
Q

suicidal inactivators: specific type of _____. they are initially __ but are converted to a ___ that ___ the enzyme.

A

irreversible enzyme inhibition;
unreactive;
reactive species;
inactive

54
Q

acetylcholinesterase is a ___ that degrade ___

A

serine protease;

acetylcholine

55
Q

serine proteases serve as ____ that __ in __ substrates; also function in __ of ___.

A 
digestive enzymes;
cleave peptide bonds;
protein;
mediating the turnover;
self proteins;
56
Q

serine proteases catalytic mechanism contains___ and ___

A

covalent;

acid-base catalysis

57
Q

serine proteases have a conserved catalytic mechanism based on a catalytic triad of residues.(__,__,__)

A

Asp; His; Ser

58
Q

two main methods to regulate enzyme activity:

A
  1. enzyme availability (long term): location, rates of synthesis and degradation
  2. enzyme activity (short term): covalent modification; non-covalent modification (allosteric)
59
Q

point of regulation: __ often inhibits __ which _______.

A

final product;
the enzyme;
catalyze the first unique and committed step of a branch point

60
Q

allosteric enzymes are regulated by ____ that ___ to the enzyme at ____.

A

allosteric modulators;
bind non-covalently;
sites distinct from the active site

61
Q

activities of allosteric regulator enzymes are changed by ___ and ___( )

A

inhibitors;
activators ;
modulators

62
Q

the binding of the substrate disrupts the ___ state to __ equilibrium in favor of ___

A

R (active)
T(inactive)
R

63
Q

threshold effect:

A

below a certain substrate concentration little enzyme activity; after the threshold has been reached the enzyme activity increases rapidly(on/off)

64
Q

allosteric enzyme activity is __ in substrate concentration ___ than are M-M enzymes of the same Vmax

A

more sensitive to changes;

near the Km

65
Q

in glycolysis, ___ is an allosteric inhibitor of phosphofructokinase 1 (PFK-1), ___ is an allosteric activator of PEK-1.

A

phosphoenolpyruvate (PEP);

ADP

66
Q

the activity of PFK-1 is responsive to____ as well as the ___ and ____.

A

substrate concentration;
allosteric activator;
inhibitors

67
Q

Covalent modification: regulate by the __ of a __ to change some aspect of the protein behavior. ( eg. ___, __, __)

A 
Covalent linkage ;
Modifying group;
Methylation;
Acetylation;
Phosphorylation
68
Q

The most common post-translation covalent modification is through __, usually __, with one enzyme (_) catalyze has the addition of the group(__) and another enzyme (__) catalyzing its removal .

A 
Phosphorylation;
Reversible;
Kinase;
Phosphoryl group;
Phosphatases;
69
Q 
Glycogen metabolism:
Glycogen synthase(\_\_) is for \_\_\_;
Glycogen phosphorylase (\_\_) is for \_\_\_.
A

Anabolic;
Catalyzing production of glycogen from glucose;
Catabolic ;
Catalyzing breakdown of glycogen into glucose

70
Q

Glycogen metabolism:
Phosphorylation of both enzymes activates__ and inactivates___;
Favors the ___.

A 
Catabolic enzyme (glycogen phosphorylase);
Anabolic enzyme ( glycogen synthase);
The breakdown of glycogen into glucose.
71
Q

Glycogen metabolism:
Unphosphorylation of both enzymes activates __ and inactivates ___.
Favors the _____

A 
Anabolic enzyme(glycogen synthase);
Catabolic enzyme (glycogen phosphorylase);
Storage of glucose within glycogen

BMSC 200 (1 decks)

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