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Biochemistry - 1 > Enzymology II > Flashcards

Enzymology II Flashcards

1
Q

Always fit each other

A

Lock and key model

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2
Q

Fit only at binding

A

Induced fit

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3
Q

The active site of the enzyme is not a rigid structure that the substrate fit precisely. T/F

A

T. It is flexible.

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4
Q

Catalytic step of Michael’s menten theory

A

ES to EP

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5
Q

Rate limiting step of Michael menten theory.

A

Step 2: fate of ES

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6
Q

A quantitative description of kinetics of enzyme-catalyzed
reactions.

A

Michael menten equation

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7
Q

In a typical enzyme catalyzed reaction, reactants and products are hundreds and thousands times greater than the number of enzyme. T/F

A

T

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8
Q

[S] 1/2 Vmax

A

Km

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9
Q

Michael menten saturation curve

A

Hyperbolic or rectangular hyperbola

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10
Q

The Michael menten saturation curve is used for non-allosteric enzymes. T/F

A

T

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11
Q

S < Km. What order?

A

1st order

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12
Q

Rate is dependent on substrate concentration.

A

S < Km and S = km

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13
Q

S = km. What order?

A

1st order

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14
Q

50% of the enzymes are bound a substrate.

A

S = Km

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15
Q

Only a portion of the enzyme is ES

A

S < km

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16
Q

100% of the enzymes is saturated

A

S > km

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17
Q

S > km. What order.

A

Zero order. NOT Dependent on substrate concentration.

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18
Q

Once the Vmax has been reached, the velocity will no longer increase. T/F

A

T. It will decrease because at this point the 2nd and 3rd structures have been desaturated.

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19
Q

Half of the active sites of the enzyme is filled up.

A

Km

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20
Q

“Signature” of an enzyme

A

Km

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21
Q

There is an inverse measure of the affinity of an enzyme for a substrate. T/F

A

T

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22
Q

If there is high km, _______ affinity. Why?

A

Low. Need more substrate for it to reach km and to be saturated.

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23
Q

If there is low km, ________ affinity. Why?

A

High. Only a small amount of substrate is needed to reach vmax. Faster saturation.

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24
Q

A more precise way to measure Vmax and Km of an enzyme.

A

LINEWEAVER-BURKE DOUBLE RECIPROCAL PLOT

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25
Q

Pharmaceutical compounds (drugs) function as inhibitors of specific enzymes. T/F

A

T

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26
Q

2 types of inhibition

A

Reversible
Irreversible

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27
Q

Inhibitor that is NOT covalently bound to the enzyme and can dissociate at any moment.

A

Reversible

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28
Q

Competitive inhibition is under what type of inhibition.

A

Reversible

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29
Q

Inhibitor compete with the substrate at the binding site.

A

Competitive inhibitor

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30
Q

In competitive inhibitor, substrate and inhibitor can bind at the same time. T/F

A

False. It CANNOT bind at the same time. Isa lang pwede.

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31
Q

No product will be formed if an inhibitor binds with the enzyme. T/F

A

T

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32
Q

According to the lineweaver-Burke plot, the Vmax of competitive inhibition is:

A. Increased
B. Decreased
C. Unchanged

A

C

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33
Q

According to the lineweaver-Burke plot, the Km of competitive inhibition is:

A. Increased
B. Decreased
C. Unchanged

A

A

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34
Q

According to the lineweaver-Burke plot, the Vmax of non-competitive inhibition is:

A. Increased
B. Decreased
C. Unchanged

A

B

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35
Q

According to the lineweaver-Burke plot, the Km of non-competitive inhibition is:

A. Increased
B. Decreased
C. Unchanged

A

C

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36
Q

According to the lineweaver-Burke plot, the Vmax of uncompetitive inhibition is:

A. Increased
B. Decreased
C. Unchanged

A

B

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37
Q

According to the lineweaver-Burke plot, the Km of competitive inhibition is:

A. Increased
B. Decreased
C. Unchanged

A

B

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38
Q

Examples of drugs of competitive inhibition.

A

Malonate
Lovastatin

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39
Q

Drug that inhibits HMG-CoA reductase that is active as a rate-limiting enzyme in cholesterol synthesase.

A

Lovastatin

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40
Q

Examples of drugs of irreversible inhibition

A

Diisopropylphosphofluoridate (DIPF)
Penicillin

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41
Q

Aspirin is an example of what time of inhibition.

A

Suicide inhibition

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42
Q

Inhibitor that permanently and irreversibly inactivates or incapacitates the enzyme while forming a COVALENT BOND with protein enzyme.

A

Irreversible

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43
Q

3 types of irreversible inhibition

A

Noncompetitive inhibition
Uncompetitive inhibition
Suicide inhibition

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44
Q

Inhibits the enzyme-serine complex that is crucial to the release of choline and acetate.

A

DIPF

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45
Q

Penicillin inhibits what enzyme that is essential in bacterial cell wall.

A

Glycopeptide transpeptodase

46
Q

Inhibitor binds to allosteric binding site of the enzyme.

A

Non competitive

47
Q

Substrate binding to active site is unaltered.

A

Non competitive inhibition

48
Q

Inhibitor binds only to ES complex.

A
49
Q

How can non competitive inhibition be overcomed?

A

Synthesis of new enzyme

50
Q

How can uncompetitive inhibition be overcomed?

A

Synthesis of new enzyme

51
Q

Drug: Captopril
Enzyme: Anguotensin - converting enzyme (ACE)
Disease:?

A

Hypertension

52
Q

Drug: Digoxin
Enzyme: ?
Disease: cardiac problem

A

Na+ k+ - ATPase pump

53
Q

Drug: lipitor & atorvastatin
Enzyme:
Disease: hypercholesterolemia

A

HMG-CoA reductase

54
Q

Drug:
Enzyme: xanthin oxidase
Disease: gout

A

Allopurinol

55
Q

Drug: sildenafil (viagra)
Enzyme: ?
Disease: erectile disfunction

A

Phosphodiesterase

56
Q

Drug:
Enzyme: protease
Disease: AIDS

A

Agenerase

57
Q

Atorvastatin and lipitor is what type of drug.

A

Statins

58
Q

Inhibits phosphodiesterase and converts cGMP to GMP.

A

Viagra

59
Q

Allosteric enzyme exhibit what type of curve?

A

Sigmoid curve

60
Q

Substrate: hyperbolic curve
Allosteric enzyme: _______

A

Sigmoid curve on a REACTION VELOCITY.

61
Q

Allosteric enzymes is usually the slowest step in the reaction, catalyze irreversible reactions. T/F

A

T

62
Q

Allosteric enzyme causes conformational change via protein enzyme bulk. T/F

A

T

63
Q

” negative feedback” or “end product inhibition”

A

Feedback inhibition

64
Q

Prevents the accumulation of intermediate products that can lead to harmful effects to the metabolism

A

Feedback inhibition

65
Q

Examples of feedback inhibitions

A

Succinyl CoA
Cholesterol

66
Q

Feedback inhibitor of krebs cycle

A

Succinyl CoA

67
Q

Feedback inhibitor of HMG-CoA reductase

A

Cholesterol

68
Q

Allosteric modification is the conformational change of the enzyme as allosteric enzymes bind to active site. T/F

A

T

69
Q

2 types of allosteric modification

A

Positive/stimulatory
Negative/inhibitory

70
Q

Allosterically active PFK 1 = ______ glycolysis rate

A

Increases

71
Q

Allosterically inhibit PFK 1 = ________ glycolysis rate

A

Decrease

72
Q

Additional or removal of a group by cleaving covalent bond to the enzyme protein.

A

Covalent modification

73
Q

Active when phosphorylated ; inactive when dephosphorylated

A

Anabolic/biosynthetic enzyme

74
Q

Active when dephosphorylated ; inactive when phosphorylated

A

Catabolic/degradative enzymes

75
Q

PFK is an anabolic enzyme in the synthesis of ATP via glycolysis. T/F

A
76
Q

Pyruvate dehydrogenase is catabolic or anabolic?

A

Catabolic

77
Q

Inactive precursors of enzymes

A

Zymogen

78
Q

Cleavage of zymogen results to activation or inactivation?

A

Activation

79
Q

Example of zymogen activation

A

Blood coagulation

80
Q

Increase in the rate of enzyme synthesis

A

Induction

81
Q

Enzyme concentration is independent of inducers

A

Constitutive enzymes

82
Q

Enzymes concentration that is dependent of inducers

A

Inducible enzymes

83
Q

Feedback inhibitors are actually the products. T/F

A

T. Such as succinyl coa and cholesterol

84
Q

Low molecular weight substances that decrease enzyme synthesis

A

Repressors

85
Q

Factors that affect enzyme activity

A

Tempt
pH
Cofactor
Substrate concentration.

86
Q

Velocity before optimum temperature is reached increases. T/F

A

T

87
Q

Velocity after optimal tempt increases still. T/F

A

F. It decreases as enzymes are desaturated at very high temperature, more than 37 degrees.

88
Q

A 10 degrees rise in temperature increases the activity of the enzyme by _____

A

50 - 100%

89
Q

Optimum tempt of for human enzymes

A

37 degrees

90
Q

Is thermal denaturation reversible or irreversible?

A

Irreversible

91
Q

Optimal pH for enzyme activity

A

5-9

92
Q

Before optimum pH is reached, velocity increases. T/F

A

T

93
Q

Why does velocity increase as an enzyme reaches an optimal pH.

A

Due to ionization of functional group of Amino acids

94
Q

After the optimum pH is reached, velocity decreases. T/F

A

T

95
Q

Why does velocity of the enzyme decrease after it reaches optimal pH?

A

Deprotonation of amino terminal group

96
Q

Cofactors increase the rate of enzyme-catalyzed rxn. T/f

A

T

97
Q

When the Vmax is reached, any increase in substrate will not change the velocity of the reaction. T/F

A

T. Reaction Velocity decreases after Vmax is met.

98
Q

Why is there a decreased reaction Velocity after Vmax is met?

A

Excess substrate present accumulates and blocks or impedes ES complex formation

99
Q

How does Atorvastatin® as a competitive inhibitor of
HMG CoA reductase decrease cholesterol synthesis?
a. Binds to the active site of the enzyme
b. Binds to the allosteric site of the enzyme
c. Promotes the inactivation of the enzyme
d. Increases the Km of the enzyme

A

A

100
Q

Which among the following do not occur during Competitive Enzyme Inhibition?
a. Vmax Unchanged
b. Substrate and Inhibitor bind at the same time
c. KmIncrease
d. Cross 1/Vmax of Lineweaver-Burke Plot

A

B

101
Q

Which among the following inhibitors are reversible?
a. Lovastatin
b. Penicillin
c. Aspirin

A

A

102
Q

The Michaelis-Menten constant Km represents which of the following?
a. Dissociation constant of the ES complex
b. [Substrate] at Vmax
c. [Substrate] at Vmax/2
d. Vmax at highest [substrate]

A

C

103
Q
  1. What happens when enzymes are heated to very high temperatures?
    a. Velocity increase in velocity due to denaturation.
    b. They function more efficiently
    c. Velocity decreases in velocity due to denaturation.
    d. Rate of the reaction increases.
A

C

104
Q

The primary role of a cofactor is:
a. To slow the reaction down
b. Assist enzymes in turning substrates into products
c. Modify the function of the enzyme
d. Increase the activation energy

A

B

105
Q

Which of the ff is TRUE about the characteristics/attributes of HMG CoA reductase as a rate-limiting enzyme?
a. Activity is not affected by number of allosteric molecules
b. Catalyzes the first irreversible step of a metabolic pathway
c. Catalyzes the slowest reaction in a multi-step pathway
d. Favors a highly spontaneous and irreversible reaction

A

C

106
Q

Which regulatory mechanism affects HMG CoA reductase activity in a patient with hypercholesterolemia?
a. Allosteric (Non Covalent modification)
b. Feedback inhibition
c. Induction or Repression of enzyme synthesis
d. Reversible covalent modification
e. Zymogen activation

A

B

107
Q

Which of the following are components of the active site of the HMG CoA reductase, EXCEPT?
a. Allosteric effectors
b. Amino acids in the active site
c. Coenzymes
d. Prosthetic groups

A

A

108
Q

Choose the CORRECT enzyme classification: chemical reaction catalyzed pair for HMG CoA reductase
a. Isomerase : transfer of PO4 group from ATP to an acceptor
b. Kinase : transfer of functional group within the same molecule
c. Lyase: condensation of two substrates in the presence of ATP
d. Oxidoreductase : transfer of an H to an acceptor molecule

A

D

109
Q

Denaturation is an effect of which factor affecting the activity of HMG CoA reductase?
a. Cofactor
b. pH
c. Substrate concentration
d. Temperature

A

D

110
Q
  1. HMG CoA reductase accelerates a chemical reaction in the biologic system via: *
    a. Changing the concentration of the reactants and products.
    b. Changing the equilibrium constant of the reaction.
    c. Inducing a conformational change in the substrate.
    d. Lowering the energy of activation of the reaction.
A

D

Biochemistry - 1 (6 decks)

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