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Biochemistry - 1 > Enzymology I > Flashcards

Enzymology I Flashcards

1
Q

Lowers the activation energy in a reaction

A

Enzymes

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2
Q

Enzymes makes the reaction _________ times faster than uncatalyzed reactions

A

106 to 1020

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3
Q

Enzymes are made up of specialised proteins. T/F

A

T

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4
Q

Enzyme during chemical reaction gets used up. T/F

A

F

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5
Q

Not all enzymes are proteins. T/F

A

T

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6
Q

all enzymes need cofactors to be activated. T/F

A

F

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7
Q

● Protein part of an enzyme without cofactors or prosthetic groups
● Gives the 3-dimensional structure

A

Apoenzyme

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8
Q

Catalytically inactive ❗️ and heat-labil

A

Apoenzyme

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9
Q

● a.k.a cosubstrates
● Usually synthesized by vitamins

A

Coenzymes

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10
Q

Is coenzyme monogamous or polygamous.

A

Poly

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11
Q

most vitamins function as a coenzyme. T/F

A

T

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12
Q

3 groups of cofactors

A

A. Coenzyme
B. Prosthetic Group
C. Metal Ions

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13
Q

Small organic or inorganic molecules
● Soluble non-protein components needed by apoenzyme
for its activity

A

Cofactor

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14
Q

Can cofactors undergo regeneration?

A

Yes

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15
Q

2 types of vitamin deficiency

A

Functional deficiency
Dietary deficiency

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16
Q

drugs and toxins that inhibits proteins required for coenzyme synthesis

A

Functional deficiency

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17
Q

Dietary deficiency

A

inadequate intake of vitamin

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18
Q

a.k.a Iron-sulfur clusters
● Inorganic molecules

A

Metal ions

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19
Q

Metal ions are involved in what chemical rxn?

A

electron transfer reactions

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20
Q

Is metal ions monogamous or polygamous?

A

Mono

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21
Q

● Organic molecule
● Firmly and permanently attaches to an apoenzyme
(monogamous)

A

Prosthetic grp

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22
Q

Classify the following based on the type of cofactors:

Biotin (B7)

A

Prosthetic group

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23
Q

Classify the following based on the type of cofactors:

NAD+

A

Coenzyme - oxidation reduction coenzyme

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24
Q

Classify the following based on the type of cofactor:

Pyridoxal phosphate (PLP),

A

Prosthetic group

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25
Q

Classify the following based on the type of cofactor:

Thiaminepyrophosphate (TPP), and lipoic acid

A

Prosthetic group

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26
Q

Apoenzyme + Cofactor

A

Holoenzyme

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27
Q

Completely catalytic active enzyme

A

Holoenzyme

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28
Q

● a.k.a Key Enzyme
● Catalyzes the rate-limiting or committed step

A

Regulatory enzyme

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29
Q

The rate limiting step is considered to be the _______ reaction in a metabolic process

A

Slowest

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30
Q

The site or region on an enzyme where substrates bind
and where the enzyme-substrate complex (ES complex)
forms, allowing it to catalyze a reaction

A

Active site

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31
Q

Active site is located in

A

Clefts and crevices

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32
Q

The surface of an enzyme is lined with functional groups and catalytic group. T/f

A

T

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33
Q

● Region that is physically separated from catalytic site of an
enzyme
● Where allosteric modifiers and effectors bind

A

Allosteric site

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34
Q

Goal of allosteric enzymes

A

To induce conformational change in the enzyme

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35
Q

___________ allosteric effectors: enhances activity of catalytic
site; stimulate the enzyme

A

Positive

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36
Q

___________ allosteric effectors: changes the conformation of
the active site to inhibit the activity of the enzyme

A

Negative

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37
Q

Term used for reactant

A

Substrate

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38
Q

Classifications of coenzyme

A

→ Activation-Transfer Coenzymes

→ Oxidation-Reduction Coenzymes

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39
Q

Oxidation-Reduction Coenzymes. Examples:

A

NAD+, FAD, Vit. E

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40
Q

Derived from Vitamin B5 (Pantothenic acid).

A

Coenzyme A (5 Yr old boy loves Apples)

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41
Q

Coenzyme A take part in what reactions

A

CAC, FA synthesis and oxidation, acylations and cholesterol synthesis.

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42
Q

→ α- Ketoglutarate → succinyl CoA

A

α- Ketoglutarate Dehydrogenase Complex Reaction

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43
Q

Pyruvate → Acetyl CoA

A

Pyruvate Dehydrogenase Complex

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44
Q

Derived from Vitamin B3 (Niacin)

A

NAD+ & NADP+

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45
Q

→ Catalyzes alcohols to ketones oxidation
→ Example: Lactate to pyruvate

A

NAD-dependent dehydrogenase:

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46
Q

NADP

A

reductive synthesis pathways

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47
Q

Thiamine pyrophosphate

A

● Derived from Vitamin B1 (Thiamine)
● Synthesized in human cells

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48
Q

Cofactor in energy-yielding metabolism

A

Thiamine pyrophosphate (TPP)

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49
Q

TPP has a carbon-reactive functional group which serves as a carrier of ketone groups in metabolism.

A

No. ALDEHYDE GROUP DAPAT

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50
Q

Special roles of TPP

A

→ Transketolase reaction in PPP
→ Oxidative decarboxylation reactions in CAC
→ Catabolism of the branched-chain amino acids

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51
Q

(Vitamin B7)
● Prosthetic group

A

Biotin

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52
Q

Cofactors of carboxylases

A

Biotin

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53
Q

Enzyme: pyruvate carboxylase

Role

A

Convert pyruvate to oxaloacetate. Primary substrate of gluconeogenesis.

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54
Q

Enzyme: Acetyl-CoA carboxylase

Role

A

→ Acetyl-CoA to Malonyl-CoA
▪ De Novo Synthesis of Fatty Acids

55
Q

Active form of biotin

A

Active form: Biocytin

56
Q

Derived from Vitamin B2 (Riboflavin)

A

FAD

57
Q

Coenzyme of dehydrogenases

A

FAD

58
Q

FAD is important in the following rxns:

A

CAC
Beta oxidation
Nitric oxide synthesis

59
Q

FAD is a stronger oxidizing agent than NAD. T/F

A

T

60
Q

Derived from Vitamin B6 (Pyridoxine)

A

Pyridoxal Phosphate (PLP)

61
Q

Major cofactor in transamination reactions

A

PLP

62
Q

PLP is important in the following:

A

Important in the following:
→ Heme synthesis
→ Transamination
→ Histamine synthesis
→ Neurotransmitter synthesis

63
Q

Metal ions cofactor:

Carbonic anhydrase

A

Zn+2

64
Q

Metal ions cofactor:

Hexokinase, pyruvate kinase, G6PD, Enolase, glycosyltransferase, phosphoglucomutase

A

Mg+2

65
Q

Metal ions cofactor:

Lipase

A

Ca+2

66
Q

Metal ions cofactor:

Urease

A

Ni+2

67
Q

Metal ions cofactor:

Salivary amylase

A

Cl-

68
Q

Metal ions cofactor:

Cytochrome oxidase
Catalase
Peroxidase

A

Fe+2

69
Q

Metal ions cofactor:

Pyruvate kinase
Propionyl CoA carboxylase

A

K+

70
Q

Cofactor of Hexokinase or Glucokinase

A

Mg2+

71
Q

6 major classes of enzymes

A

H - Hydrolases
I - Isomerases
L - lyases
L - ligase
O - oxidoreductases
T - transaminases

72
Q

Transfer of electrons and hydrogen atoms

A

OXIDOREDUCTASES

73
Q

Transfer functional groups other than hydrogen (like C-, N-,
or P-) from donors to acceptors
● Utilizes 2 substrates to produce 2 products

A

TRANSFERASE

74
Q

Catalyze cleavage of chemical bonds (ester, ether, peptide or glycosidic bonds) by addition of H2O, producing 2 products

A

HYDROLASES

75
Q

All digestive enzymes are hydrolases. T/f

A

T

76
Q

Cleaves C-C, C-O, C-N bonds by means other than hydrolysis or oxidation (no addition of H2O)❗

A

LYASES

77
Q

Rearrange bond structure of a compound 📖[Marks]
● Catalyze the transfer of functional groups or double bonds
within the same molecule or catalyze racemization of
optical or geometric isomers

A

ISOMERASES

78
Q

Catalyze ligation or joining of 2 substrates with covalent
bonds

A

LIGASES

79
Q

Classify type of enzyme:

Dehydrogenase

A

Oxidoreductase

80
Q

Classify type of enzyme:

Kinases

A

Transferase

81
Q

Classify type of enzyme:

Peroxidases

A

Oxidoreductase

82
Q

Classify type of enzyme:

Esterases

A

Hydrolases

83
Q

Classify type of enzyme:

Thiolases

A

Hydrolases

84
Q

Classify type of enzyme:

Decarboxylases

A

Lyases

85
Q

Classify type of enzyme:

Aldolases

A

Lyases

86
Q

Classify type of enzyme:

L-alanine to D-alanine

A

Isomerases

87
Q

Classify type of enzyme:

Pyruvate carboxylase

A

Ligases

88
Q

Classify type of enzyme:

DOPA decarboxylase

A

Lyases

89
Q

Cleaves C-C bond and released as CO2, DOPA is decarboxylated as Dopamine❗

A

DOPA decarboxylase

90
Q

Lyases generate either a double bond or a ring structure but DO NOT ALWAYS generate a double bond. T/F

A

T

91
Q

Transfers the functional group phosphate from ATP to anacceptor molecule❗

A

Kinases

92
Q

Glucose to G6PD is highly spontaneous thus it is what type of rxn? Endergonic or exergonic?

A

Exergonic

93
Q

Addition of H2O to a substrate

A

Hydratase

94
Q

First step in gluconeogenesis

A

Pyruvate carboxylase

95
Q

Enzymes Can be temporarily changed or modified during reaction. T/F

A

T

96
Q

Enzymes are generated or recycled or return to their original
form. T/F

A

T

97
Q

ENZYMES INCREASE REACTION RATES BY DECREASING ACTIVATION ENERGY. T/F

A

T

98
Q

Axis where reaction progress that represents progressive bond breakage/ formation

A

X axis

99
Q

Axis where free energy, ΔG

A

Y axis

100
Q

→ rate limiting step of the overall reaction
→ has a higher free energy than either substrate or
product

A

Transition state (S=/)

101
Q

→ rate limiting step of the overall reaction

A

Transition state

102
Q

Activation energy =/

A

difference in free energy between the transition state and substrate

103
Q

represents the difference between the energies of the reactants and the energies of the products

A

Activation energy

104
Q

formation of the transition state from substrate is endergonic or exergonic?

A

Endergonic

105
Q

If the transition from substrate to transition state is endergonic, what is the overall reaction?

A

Exergonic

106
Q

enzyme catalyzes only on a single chemical reaction. T/F

A

T

107
Q

Catalyzes only one reaction.

A

Absolute Specificity.

Examples: Carbonic Anhydrase, Catalase, Glucokinase

108
Q

highly specific for glucose

A

Glucokinase

109
Q

Can catalyze the phosphorylation of the hexoses glucose, galactose and mannose.

A

Group Specificity

110
Q

Recognizes only the L-isomer of lactate but not the D-isomer

A

Stereospecificity

Example: lactate dehydrogenase

111
Q

Most Enzymes are made up of proteins. Therefore they are bonded by peptide bonds. T/F

A

T

112
Q

unfolding of proteins with the use of acid or base, chaotropic agents or detergents

A

Denaturation

113
Q

thermal denaturation of the enzyme is reversible or irreversible?

A

Irreversible

114
Q

What occurs in vmax?

A

all enzymes have been saturated (all enzymes have been “partnered” with a substrate)

115
Q

When the rxn reaches vmax, does this represent the E-S complex?

A

Yes

116
Q

rate of chemical reaction

A

Reaction velocity

117
Q

Competitive Inhibition

A

Inhibitor binds to ENZYME to block substrate.

118
Q

Non-Competitive Inhibition

A

Inhibitor binds to SUBSTRATE. Binding could still occur but there is decreased catalytic activity due to conformational change.

119
Q

substrate binds to a site whose shape complements its own.

A

Lock and Key Model

120
Q

Lock and Key Model is developed by

A

Fischer

121
Q

does not take into account the 3-dimensional flexibility of
proteins → the key acts on the lock but not vice versa
→ Enzymes are not rigid or static structures, the lock
should also act on the key

A

Lock and key

122
Q

substrate and enzyme fit only at binding ❗.
Enzyme undergoes a slight conformational change
(“induced fit”) on binding to the substrate

A

Koshlands induce fit model

123
Q

Enzyme forms a complementary shape or flexible pocket that approximates substrate’s shape

A

Induce fit model

124
Q

The induct fit model is induced by what bond

A

Hydrogen bond

125
Q

The Michaelis-Menten constant Km represents which of
the following kinetic relationships?
A. Dissociation constant of the ES complex.
B. [Substrate] at Vmax.
C. [Substrate] at Vmax/2.
D. Vmax at highest [substrate]

A

C

126
Q

Which of the following is the catalytically active
enzyme?
A. Coenzyme
B. Holoenzyme
C. Metal ion
D. Prosthetic group

A

B

127
Q

Denaturation is an effect of which factor affects the
activity of HMG CoA reductase?
A. Cofactor
B. pH
C. Substrate concentration
D. Temperature

A

D

128
Q

Which of the following is TRUE about the
characteristics/attributes of HMG CoA reductase as a
rate-limiting enzyme?
A. Activity is not affected by a 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

129
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

130
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

131
Q

Catalyze cleavage of high-energy phosphate bond of
pyrophosphate (PPi) in the presence of H2O, forming 2
inorganic phosphates (2 Pi)

A

Pyrophosphatase

132
Q

a substance that mediates inflammatory and allergic conditions

A

Histamine

133
Q

Histidine decarboxylase

A

Catalyzes the removal of carboxyl group of histidine to
produce histamine in the presence of PLP as a cofactor

134
Q

Catalyzes transfer of OH at the left side of carbon 3 of
D-xylulose 5-phosphate to the right side, forming
D-ribulose 5-phosphate

A

Epimerase

Biochemistry - 1 (6 decks)

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