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Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Which enzyme classification that does not use water to remove a functional group

A. Lyases
B. Ligases
C. Hydrolases
D. None of the above

A

A.

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2
Q

Most reduced form:

A. Ketone
B. Carboxyl
C. Methyl
D. Alcohol

A

C.

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3
Q

True of metalloenzyme

A. Coenzyme
B. Dissociable
C. Metal associated enzyme
D. Prosthetic group

A

D.

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5
Q

The effect of temperature on an enzyme-catalyzed reaction is represented by:

A. Sigmoid curve
B. Bell-shaped curve
C. Hyperbolic curve
D. Straight line

A

B

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6
Q

Which is the correct 4-digit IUBMB

A. Mechanism - substrate class - enzyme group - specific substrate
B. M - eg - sc - ss
C. Eg - ss - sc - m
D. Eg - m - sc - ss

A

D.

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7
Q

Most oxidized form:

A. Ketone
B. Carboxyl
C. Methyl
D. Alcohol

A

B.

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8
Q

Which of the following is not catabolic

A. Hydrolases
B. Lyases
C. Ligases
D. All are catabolic

A

C.

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9
Q

Which of the following is neither catabolic nor anabolic

A. Transferases
B. Isomerases
C. Lyases
D. Ligases

A

B.

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10
Q

Which of the ff is matched correctly

A. Lock & key - cytochrome p450; induced fit - hexokinase
B. Lock & key - urease; induced fit - cytochrome p450
C. Lock & key - hexokinase; induced fit - cytochrome p450
D. Lock & key - cytochrome p450; induced fit - urease

A

B.

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11
Q

Which is not part of the catalytic triad

A. Histidine
B. Aspartate
C. Serine
D. Cysteine

A

D.

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13
Q

True of co-factors

A. Coenzyme
B. Prosthetic group
C. Both A & B
D. Neither A nor B

A

C.

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14
Q

Not true of co-factors

A. Participate in substrate binding
B. Participate in catalysis
C. Non-protein
D. Protein

A

D.

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15
Q

Most co-enzymes come from

A. Vitamin A
B. Vitamin B
C. Vitamin C
D. Vitamin D

A

B.

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16
Q

Coenzyme involved in oxidoreduction

A. CoA
B. TPP
C. FMN
D. PLP

A

C.

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17
Q

Catalytic triad: strong nucleophile, attacks carbonyl C

A. Histidine
B. Cysteine
C. Serine
D. Tyrosine

A

C.

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18
Q

Coenzyme involved of Vitamin B1

A. FMN
B. THF
C. TPP
D. CoA

A

C.

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20
Q

Enzymes starts to denature at temperature = _____ degree celsius

A. 35-45
B. 40-50
C. 45-55
D. 50-60

A

C.

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21
Q

Catalytic triad: accts proton from Ser

A. Histidine
B. Aspartate
C. Cysteine
D. Lysine

A

A.

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22
Q

Catalytic triad: stabilizes protonated Histidine

A. Serine
B. Lysine
C. Arginine
D. Aspartate

A

D.

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23
Q

Substrate conc vs reaction rate is represented by

A. Bell-shaped curve
B. Sigmoidal curve
C. Hyperbolic curve
D. Straight line

A

C.

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24
Q

Rate of enzyme-catalyzed reactions in humans doubles with every increase of _____ degree celsius

A. 10
B. 20
C. 30
D. 40

A

A.

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25
Q

In the substrate conc vs reaction rate plot, enzyme saturation is equal to

A. Vi
B. Vmax
C. Km
D. [S]

A

B.

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26
Q

Inhibition results to increase in substrate concentration.

A. Suicide
B. Competitive
C. Nomcompetitive
D. Uncompetitive

A

B.

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27
Q

Non vitamin derived coenzyme

A. Nicotinamide
B. Ubiquinone
C. Flavin
D. Biocytin

A

B.

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28
Q

Substrate conc at half the maximal velocity

A. [S]
B. Vmax
C. V
D. Km

A

D.

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29
Q

Double reciprocal plot

A. Eadie-Hofstee
B. Hanes-Woolf
C. Lineweaver-Burk
D. Both A & B

A

C.

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30
Q

Single reciprocal plot

A. Eadie-Hofstee
B. Hanes-Woolf
C. Lineweaver-Burk
D. Both A & B

A

D.

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31
Q

The larger the turnover number,

A. Slower reaction
B. Faster reaction
C. Equilibrium
D. Reaction rate not affected

A

B.

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32
Q

Catalytic efficiency

A. Km/Kcat
B. Km + Kcat
C. Kcat/Km
D. Km - Kcat

A

C.

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33
Q

Describe the behavior of enzyme-exhibiting cooperativity

A. Lineweaver-Burk plot
B. Michaelis constant
C. Eadie-Hofstee plot
D. Hill equation

A

D.

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34
Q

One or more products are released before all substrates are added

A. Double displacement rx
B. Ordered sequential rx
C. Random sequential rx
D. Redox rx

A

A.

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35
Q

Any of the substrates combine first followed by the other –> catalysis

A. Double displacement rx
B. Ordered sequemstial rx
C. Random sequential rx
D. Redox rx

A

C.

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36
Q

One substrate must bind first with the enzyme –> complex –> other substrate can now bind –> catalysis

A. Double displacement rx
B. Ordered sequential rx
C. Random sequential rx
D. Redox rx

A

B.

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37
Q

“Ping-Pong reaction”

A. Double displacement rx
B. Ordered sequential rx
C. Random sequential rx
D. Redox rx

A

A.

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38
Q

Inhibition that has no effect on the value of Km but lowers the Vmax

A. Suicide
B. Competitive
C. Noncompetitive
D. Uncompetitive

A

C.

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39
Q

“Compulsory reaction”

A. Double displacement rx
B. Ordered sequential rx
C. Random sequential rx
D. Redox rx

A

B.

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41
Q

Reaction that produces intersecting Lineweaver-Burk plots

A. Single displacement
B. Double displacement
C. Both
D. Neither

A

A.

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42
Q

Reaction that produces parallel Lineweaver-Burk plot

A. Single displacement
B. Double displacement
C. Both
D. Neither

A

B.

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43
Q

Inhibition that lowers both the value of Km and Vmax

A. Suicide
B. Competitive
C. Nomcompetitive
D. Uncompetitive

A

D.

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44
Q

Inhibition that has no effect on Vmax but increases the Km

A. Suicide
B. Competitive
C. Nomcompetitive
D. Uncompetitive

A

B

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45
Q

In the Lineweaver-Burk plot, the normal line and the inhibited line intercept at the x-axis

A. Competitive
B. Nomcompetitive
C. Uncompetitive
D. Both B & C

A

B.

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46
Q

Inhibitors that bind either to the free enzyme or ES complex

A. Suicide
B. Competitive
C. Noncompetitive
D. Uncompetitive

A

C.

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47
Q

In the Lineweaver-Burk plot, the normal line and the inhibited line intercet at the y-axis

A. Competitive
B. Nomcompetitive
C. Uncompetitive
D. Both B & C

A

A.

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48
Q

In the Lineweaver-Burk plot, the normal line and the inhibited line never intercept (parallel)

A. Competitive
B. Noncompetitive
C. Uncompetitive
D. Both B & C

A

C.

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49
Q

Statin is an example of

A. Competitive inhibitor
B. Noncompetitive
C. Uncompetitive
D. Mechanism based

A

A.

50
Q

If delta G is positive

A. Exergonic
B. Energy requiring
C. Equilibrium
D. No net change

A

B.

51
Q

Inhibitors that bind to the active site, preventing ES complex formation

A. Suicide
B. Competitive
C. Nomcompetitive
D. Uncompetitive

A

B.

52
Q

Which drug is not a competitive inhibitor

A. Captopril
B. Lovastatin
C. Methotrexate
D. Aspirin

A

D.

53
Q

Which drug is not a suicide inhibitor

A. Penicillin
B. Captopril
C. Aspirin
D. 5-fluorouacil

A

B.

54
Q

Phosphorylation of this aminoacyl residue can alter the catalytic efficiency of enzymes

A. Cysteine
B. Glutamate
C. Serine
D. Hydroxyproline

A

C.

55
Q

An enzyme that adds a phosphate group

A. Phosphorylase
B. Phosphotransferase
C. Kinase
D. Both B & C

A

D.

56
Q

Not true of proenzyme

A. Fast method of modifying enzyme activity
B. Reversible
C. Process by which zymogens are activated
D. Activated by inhibiting gene represson

A

B. It is irreversible

57
Q

Not true of coenzymes

A. Protein in nature
B. Chemically altered during reactions
C. Derived from water soluble vitamins
D. Reaction specific

A

A.

58
Q

Enzymes are

A. Substrate-specific
B. Stereo-specific
C. Reaction-specific
D. All are true

A

D.

59
Q

Not true of Active site

A. Recognition site
B. Shield substrate from water
C. Lowers catalysis
D. Provides the environment for chemical transformation

A

C. Catalysis are higher becuase of active site for it can shield substrate from water and it can also generate an envt with different polarity hydrophobicity acidity alkalinity from the cytoplasm

60
Q

Gene regulators are often

A. Metals
B. Proteins
C. Hormones
D. All of the above

A

C.

62
Q

Reaction for which the ONLY participating acid/base are proton/hydroxide ion, respectively

A. General acid/base catalysis
B. Specific acid/base catalysis
C. Covalent catalysis
D. Both A & B

A

B.

63
Q

Reaction which causes modification of enzyme resulting in lower activation energy and faster reaction

A. General acid/base
B. Specific acid/base
C. Covalent
D. Both A & B

A

C.

64
Q

In covalent catalysis, the ff are characteristics of the modified enzyme except

A. Transient
B. Lowers the activation energy
C. Permanent
D. Makes the reaction faster

A

C.

65
Q

Residues that participate in ping-pong mechanism

A. Serine
B. Histidine
C. Aspartate
D. Cysteine

A

C.

66
Q

Digestive enzyme that are not produced by the HIV virus

A. Pepsin
B. Lysosomal cathepsins
C. Aspartic Proteases
D. None of the above

A

D.

67
Q

The trio that forms charge relay network, proton shuttle, except

A. Asp 102
B. His 57
C. Ser 76
D. Ser 195

A

C.

68
Q

The regulatory enzyme of gluconeogenesis

A. Fructose 2-6 bisphosphatase
B. Glucose 6 bisphosphatase
C. Both
D. Neither

A

A.

69
Q

Troponins is a complex of three proteins involved in muscle contraction in

A. Skeletal muscle
B. Cardiac muscle
C. Smooth muscle
D. Both A & B

A

D.

70
Q

Gibbs free energy change can be represented as

A. Delta Gp + Delta Gs
B. Delta Gp - Delta Gs
C. Delta Gs - Delt Gp
D. Delta Gs / Delta Gp

A

B.

71
Q

Which of the ff statement regarding substrate conc vs reaction rate is true

A. High [S] –> low reaction rate
B. Vi depends solely on the rapidity with which product dissociates from the enzyme
C. Vi is indirectly proportional to [S] until it reaches Vmax
D. At Vmax, there are no excess substrate

A

B.

72
Q

In regulating enzyme activity, the ff are true except

A. Enzymes are affected by pH and temperature because they are mostly made up of AA
B. Temperature and pH changes affect other enzymes that do not require regulation
C. Altering pH and temperature is a good mechanism for regulating enzyme activity
D. All are true

A

C. Not good becase of letter B

73
Q

Type of Allosteric effector, effector is different from the substrate

A. Homotropic
B. Positive
C. Heterotrophic
D. Negative

A

C.

74
Q

Effector that reduce catalytic activity

A. Homotrophic
B. Positive
C. Heterotrophic
D. Negative

A

D.

75
Q

With allosteric activators the velocity will ___ @ ___ [S]

A. Increase, higher
B. Decrease, lower
C. Increase, lower
D. Decrease, higher

A

C.

77
Q

Activators

A. Heterotrophic
B. Homotrophic
C. Positive
D. Negative

A

C.

78
Q

Allosteric effector, substrate itself serve as an effector

A. Heterotrophic
B. Homotrophic
C. Positive
D. Negative

A

B.

79
Q

ATP + AMP –> 2ADP

A. Acyl CoA synthetase
B. Adenylate kinase
C. Glycerol kinase
D. Creatine kinase

A

B.

80
Q

With the addition of positive allosteric effector the line on the graph will shift to the

A. Right
B. Left
C. No effect
D. No answer

A

B.

81
Q

Not true of allosteric enzyme

A. With 2 or more protein chains
B. Tertiary structure
C. Has substrate binding site
D. Has regulatory site

A

B. Quarternary

82
Q

With the presence of allosteric inhibitors the plot line will shift to the

A. Right
B. Left
C. No effect
D. Make a straight line

A

A.

83
Q

Compartmentation

A. Ensures metabolic efficiency
B. Simplifies regulation
C. Decreases reaction rate
D. Both A & B

A

D.

85
Q

Compartmentation in the mito matrix

A. Glycolysis
B. TCA
C. ETC
D. Oxidative phosphorylation

A

B.

86
Q

Phosphagens

A. Creatine phosphate
B. Arginine phosphate
C. Inorganic pyrophosphatase
D. Both A & B

A

D.

87
Q

RLS in gluconeogenesis

A. Fructose 1-6 bisphosphatase
B. HMG CoA reductase
C. phosphofructokinase I
D. All of the above

A

A.

88
Q

The protein component of the enzyme:

A. Coenzyme
B. Prosthetic group
C. Apoenzyme
D. Proenzyme

A

C. Apoenzyme contains the AAs

89
Q

Class I: ___ as Class II: ___

A. Cytochrome p450 reductase; FAD-containing reductase
B. FAD-containing reductase; iron sulfur protein
C. FAD-comtaining reductase; Cytochrome p450 reductase
D. Cytochrome p450; iron sulfur protein

A

C.

90
Q

Compartmentation in the cytosol

A. Oxidative phosphorylation
B. ETC
C. Glycogen synthesis
D. Beta oxidation of fatty acids

A

C.

91
Q

Non-protein catalysts which play a role in intron and tRNA processing

A. Apoenzyme
B. Coenzyme
C. Proenzyme
D. Riboenzyme

A

D.

92
Q

RLS in cholesterol synthesis

A. Fructose 1-6 bisphosphatase
B. HMG CoA reductase
C. phosphofructokinase I
D. All of the above

A

B.

93
Q

Pathways that uses NADP-linked dehydrogenases except

A. Glycolysis
B. Fatty acid synthesis
C. Steroid synthesis
D. Pentose phosphate pathway

A

A. Glycolysis and citric acid cycle are NAD-linked dehydrogenase

94
Q

The final product inhibits the committed step

A. Simple feed back
B. Co-operative
C. Multivalent
D. Sequential

A

A.

95
Q

Inhibitors (substrate analogs) that blocks the function of the catalytic subunit

A. Suicide
B. Competitive
C. Noncompetitive
D. Uncompetitive

A

A.

96
Q

In sequential inhibition, when one product inhibits its own synthesis

A. + feed back on the other product
B. - feed back on the other product
C. The synthesis of the other product is not affected
D. The production of both product will stop

A

A.

97
Q

Molecule which binds to the repressor protein making it inactive

A. Corepressor
B. Inducer
C. Both
D. Neither

A

B.

98
Q

Coenzyme of pyruvate carboxylase

A. Biotin
B. TPP
C. CoA
D. Pyridoxal phosphate

A

A.

99
Q

Blocks the structural gene by binding at the operator site

A. Corepressor
B. Inducer
C. Both
D. Neither

A

A.

100
Q

RLS in glycolysis

A. Fructose 1-6 bisphosphatase
B. HMG CoA reductase
C. phosphofructokinase I
D. All of the above

A

C.

101
Q

Enzymes that block the action of cytochrome aa3

A. CO
B. Cyanide
C. Hydrogen sulfide
D. All of the above

A

D.

102
Q

Induction: ____ as Repression: ____

A. Corepressor; inducer
B. Corepressor; repressor protein
C. Inducer; corepressor
D. Inducer; repressor protein

A

C.

103
Q

The plot for V vs [S] for an allosteric enzyme is

A. Hyperbolic
B. Sigmoidal
C. Bell-shaped
D. Straight

A

B.

104
Q

Usual sites for phosphate addition to proteins are in the R group hydroxyl residues of

A. Serine
B. Threonine
C. Tyrosine
D. All of the above

A

D.

106
Q

Recent research has indicated that cancer are cause by

A. Abnormal phosphorylation of growth factor and hormone receptors
B. Dephosphorylation of hormone receptors
C. Phosphorylation of proteins that regulate cell division
D. All of the above

A

A.

107
Q

The following enzymes have High activity in their phosphoenzyme state except

A. Citrate lyase
B. Phosphorylase b kinase
C. Glycogen synthase
D. Glycogen phosphorylase

A

C.

108
Q

The following enzymes have high activity in their dephosphoenzyme state except

A. Pyruvate dehydrogenase
B. HMG CoA reductase
C. Acetyl CoA carboxylase
D. HMG CoA reductase kinase

A

D.

109
Q

ATP acts as phosphate donor to form compounds of lower free energy of hydrolysis

A. Acyl CoA synthethase
B. Adenylate kinase
C. Glycerol kinase
D. Creatine kinase

A

C.

110
Q

Not true of Proteolysis

A. Reversible covalent modification
B. Blood clotting enzymes
C. Digestive enzymes
D. Modification of zymogen to make it active

A

A.

111
Q

Not true of Sulfa Drugs

A. First antibiotic discovered
B. Inhibits bacterial growth
C. Competitive inhibitor of PABA
D. Humans are affected becuase we use PABA for folate synthesis

A

D. We derived folate from our diet

112
Q

Inhibits transpeptidase (bacterial cell wall synthesis)

A. Sulfa drugs
B. Penicillin
C. Ciprofloxalin
D. All of the above

A

B.

113
Q

ATP directly hydrolyzed to AMP, PPi release

A. Acyl CoA synthethase
B. Adenylate kinase
C. Glycerol kinase
D. Creatine kinase

A

A.

115
Q

Inhibits DNA gyrase (kinks removal)

A. Sulfa drugs
B. Penicillin
C. Ciprofoxacin
D. Both A & B

A

C.

116
Q

If delta G is negative, the ff are true except

A. Endergonic
B. Loss of free energy
C. Spontaneous reaction
D. Both A & B

A

A.

118
Q

Will enhance flux through the pathway

A. Increase in enzymes quantity
B. Decrease in enzymes quantity
C. Decrease in catalytic efficiency
D. Both B & C

A

A. Both increase in enzymes quantity and catalytic efficiency enhances flux through the pathway

123
Q

Both final products inhibit the first step of their own synthesis together

A. Simple
B. Co-operative
C. Multivalent
D. Sequential

A

B.

165
Q

Inhibitors that binds ONLY to the ES complex

A. Suicide
B. Competitive
C. Noncompetitive
D. Uncompetitive

A

D.

Biochemistry (3 decks)

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