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Enzyme > Devlin > Flashcards

Devlin Flashcards

1
Q

Specialized proteins that function in the acceleration of chemical reactions

A

Enzymes

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2
Q

Increases the rate of a chemical reaction but is not itself changed in the process

A

Catalyst

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3
Q

True/False
Enzymes may become temporarily covalently bound to a molecule being transformed during intermediate stages of the reaction but at the end of the reaction the enzyme will again be in its original form as the product is released

A

True. (See Devlin)

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4
Q

True/False

Enzymes change the equilibrium constant of the reaction.

A

False.

They simply increase the rate at which the reaction approaches equilibrium.

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5
Q

Enzyme increases the rate at which the reaction approaches equilibrium by lowering the _______

A

Energy of activation

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6
Q

Protein part of the enzyme without any cofactors or prosthetic groups that may be required for the enzyme to be functional

A

Apoenzyme

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7
Q

Catalytically inactive part of the enzyme

A

Apoenzyme

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8
Q

Small organic or inorganic molecules that an apoenzyme requires for its activity
Loosely bound

A

Cofactor

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9
Q

Similar to a cofactor but is tightly bound to an apoenzyme

A

Prostethetic group

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10
Q

Active enzyme

Addition of a cofactor or prosthetic group to the apoprotein

A

Holoenzyme

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11
Q

Molecule acted upon by the enzyme to form product

A

Substrate

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12
Q

True or False

Enzymes have a great deal of specificity

A

True. (Devlin)

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13
Q

The specificity of the enzyme resides in a particular region on the enzyme surface, the _______, a particular arrangement of amino acid side chains in the polypeptide that is specially formulated to bind a specific substrate

A

Substrate-binding site

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14
Q

True or False

Some enzymes have broad specificity.

A

True.

Glucose, mannose and fructose are phosphorylated by hexokinase.

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15
Q

The substrate-binding site may contain the ____, which contains the machinery, in the form of particular amino acid side chains, involved in catalyzing the reaction

A

Active site

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16
Q

Enzymes that have different structures but catalyze the same chemical reaction.

A

Isoenzyme

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17
Q

Some enzymes have a region of the molecule, the ___, that is not the active site or substrate-binding site but is a unique site where small molecules bind and effect a change in the substrate-binding site or the activity occurring in the active site.

A

Allosteric site

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18
Q

True or False

The binding of specific small molecule at the allosteric site causes a change in the conformation of the enzyme

A

True.
This can cause the active site to become either more active or less active by increasing or decreasing the affinity of the binding site for substrate

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19
Q

6 major classification of enzymes

A 
Oxidoreductases
Transferases
Hydrolases
Isomerases
Ligases
Lyases
(Remember ILLHOT)
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20
Q

Catalyze oxidation-reduction reactions

A

Oxidoreductases

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21
Q

Subclasses of oxidoreductase

A 
Dehydrogenase
Oxidase
Oxygenase
Reductase
Peroxidase
Catalase
Hyroxylase
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22
Q

Transfer two electrons from the donor to oxygen, resulting usually in hydrogen peroxide

A

Oxidases

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23
Q

Catalyze the incorporation of oxygen into a substrate

A

Oxygenases

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24
Q

Utilize hydrogen peroxide rather than oxygen as oxidant

A

Peroxidase

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25
Q

Unique in that hydrogen peroxide serves as both and acceptor

A

Catalase

Catalase functions in the cell to detoxify hydrogen peroxide

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26
Q

Transfer functional groups between donors and acceptors

A

Transferase

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27
Q

Subclasses of transferases

A

Transaldolase and transketolase
Acyl, methy, glycosyl, and phosphoryltransferase
Kinases
Phosphomutases

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28
Q

Phosphorylating enzymes that catalyze the transfer of the gamma phosphoryl group from ATP or another nucleoside triphosphate to alcohol or amino group acceptors

A

Kinases

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29
Q 
A special class of transferases in which the donor group is transferred to water
Involves the hydrolytic cleavage of C-O, C-N,O-P, C-S bonds
A

Hydrolases

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30
Q

Proteolytic enzymes are a special class of hydroxylases

A

Peptidases

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31
Q

Add or remove the elements of water, ammonia, or carbon dioxide

A

Lyases

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32
Q

Subclasses of hydrolases

A 
Esterase
Glycosidases
Peptidases
Phosphatases
Thiolases
Phospholipidases
Amidases
Deaminases
Ribonucleases
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33
Q

Subclasses of lyases

A 
Decarboxylases
Aldolases
Hydratases
Dehydratases
Synthases
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34
Q

Remove the element of carbon dioxide from alpha- or beta-keto acids or amino acids

A

Decarboxylases

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35
Q

Remove water in a dehydration reaction

A

Dehydratases

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36
Q

Catalyze isomerizations of several types

A

Isomerases

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37
Q

Subclasses of isomerases

A

Racemaces
Epimerases
Isomerases
Mutases (not all)

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38
Q

Involve intramolecular transfer of a group such as a phosphoryl

A

Mutase

39
Q

Enzymes that are involved in synthetic reactions where two molecules are joined at the expense of a high-energy phosphate bond of ATP

A

Ligases

40
Q

Subclasses of ligases

A

Sythetases

Carboxylases

41
Q

True or false

Velocity of an enzyme is dependent on both substrate and enzyme concentrations

A

True

42
Q

In Michaelis-Menten equation, the ES complex is in a _______; that is, during the initial phases of the reaction, the concentration of the ES complex remains constant, even though many molecules of substrate are converted to products via the ES comple

A

Steady state

43
Q

True or False
In Michaelis-Menten equation is that under saturating conditions, enzymes are not necessarily converted to ES complexes, meaning some enzymes are free.

A

False.

The second assumption states that no enzyme is free under saturating conditions.

44
Q

According to the Michaelis-Menten equation, the rate of formation of products will be (maximal/minimal) if all the enzyme is in the ES complex.

A

Maximal

45
Q

True or False
The two constants in the rate equation, which are Vmax and Km, are unique to each enzyme under specific conditions of pH and temperature.

A

True.

46
Q

True or False.

pH and temperature have no effect in the constants Vmax and Km.

A

False.

47
Q

The linear form of the Michaelis-Menten equation is often referred to as the ______.

A

Lineweaver-Burk or double-reciprocal plot.

48
Q

True or False

An enzyme can only catalyze forward direction of a reversible reaction.

A

False.

Enzyme can catalyze the forward and reverse reactions.

49
Q

True or False
The direction of flow of material, either in the forward or the reverse direction, will depend on the concentration of substrate relative to the product and the equilibrium constant of the reaction.

A

True

50
Q

Reversibility of a pathway or a particular enzyme-catalyzed reaction is dependent on _______.

A

Rate of product removal.

51
Q

The lineweaver-Burk plot will not be linear in those cases where the enzyme is susceptible to _____.

A

Product inhibition

52
Q

A phenomenon wherein the product inhibits the reaction the concentration of product increases.

A

Product inhibition.

53
Q

True or False
Often the coenzyme has an affinity for the enzyme that is similar to that of the substrate; consquently, the coenzyme can be considered to be a second substrate.

A

True

54
Q

True or False

In some cases, the coenzyme is covalently bound to the apoenzyme and functions at or near the active site in catalysis.

A

True

55
Q

Often functions as a second substrate but can also serve as a cofactor in modulation of the activity of specific enzymes.
Synthesized de novo in all mammalian cells

A

ATP

56
Q

FAD, FMN, NAD+, NADP+

A

Coenzymes

57
Q

3 major classes of inhibitors

A

Competitive
Noncompetitive
Uncompetitive

58
Q

Inhibitors whose action can be reversed by increasing amounts of substrate

A

Competitive inhibitors

59
Q

Competitive inhibitors are structurally similar to the substrate and bind at the ____.

A

Substrate-binding site

60
Q

In the presence of competitive inhibitor: Vmax (changes, remains constant); Km (changes, remains constant)

A

Remains constant; changes

61
Q

True or False
In the presence of competitive inhibitor, the x-intercept is no longer the negative reciprocal of the true Km, but of an apparent value.

A

True

62
Q

Binds at a site other than the substrate-binding site.

Not reversed by increasing concentration of substrate

A

Noncompetitive inhibitors

63
Q

In the presence of a noncompetitive inhibitors: Vmax (changes, remains constant); Km (changes, remains constant)

A

Changes; remains constant

64
Q

Behaves as though it were removing active enzymes from the solution, resulting in a decrease in Vmax

A

Noncompetitive inhibitor

65
Q

Binds only with the ES form of the enzyme in the case of a one-substrate enzyme

A

Uncompetitive inhibitor

66
Q

In the presence of uncompetitive inhibitor: Vmax (changes, remains constant); Km (changes, remains constant)

A

Changes; changes

67
Q

Causes an equivalent shift in both Vmax and Km resulting in a line parallel to that given by the uninhibited enzyme

A

Uncompetitive inhibitor

68
Q

Binds at the substrate-binding site and effectively increases the Km for the substrate

A

Competitive inhibitor

69
Q

Binds at a site other than the substrate-binding site; therefore, the effective Km does not change, but the apparent Vmax decreases

A

Noncompetitive inhibitor

70
Q

Unique region of the enzyme quite different from the substrate-binding site

A

Allosteric site

71
Q

Ligands that bind at the allosteric site are called ___

A

Allosteric effectors

72
Q

Binding of an allosteric effector causes a ______ of the enzyme so that the affinity for the substrate or other ligands also changes.

A

Conformational change

73
Q

Increase the enzyme affinity for substrate or other ligand

A

Positive allosteric effectors

74
Q

Decrease the enzyme affinity for substrate or other ligand

A

Negative allosteric effectors

75
Q

The allosteric site at which the positive effector binds is referred to as an _____; the negative effector binds at an ____.

A

activator site; inhibitory site

76
Q

Allosteric enzyme exhibits ____ kinetics

A

Sigmoidal

77
Q

Any molecule that is bound to a macromolecule

Can be activators, inhibitors or even the substrate of enzymes

A

Ligand

78
Q

Those ligands that change enzymatic activity, but are uncharged as a result of enzyme actions, are referred to as ___, ____ and ____.

A

Effectors
Modifiers
Modulators

79
Q

Most of the enzymes subject to modulation by ligands are ____ enzymes in metabolic pathways.

A

Rate-determining

80
Q

Allosteric enzymes are divided into classes based on the effect of the allosteric effector on the __ and ___.

A

Km and Vmax

81
Q

Effector alters the Km but not Vmax

A

K class

82
Q

Effector alters the Vmax but not Km

A

V class

83
Q

Class of allosteric enzymes

Noncompetitive inhibitors

A

V class

84
Q

Class of allosteric enzymes

Gives double-reciprocal plots like those of competitive inhibitors

A

K class

85
Q

Class of allosteric enzymes

Negative effector binding at an allosteric site affects the affinity of the substrate-binding site for the substrate

A

K class

86
Q

Class of allosteric enzymes

Positive and negative allosteric modifiers increase or decrease the rate of breakdown of the ES complex to products

A

V class

87
Q

As a consequence of interaction between substrate site, activator site and inhibitor site, a characteristic ____ is obtained in [substrate] versus v plots of allosteric enzyme

A

S-shape

88
Q

(Positive/Negative) allosteric effectors move the curve toward higher substrate concentrations and enhance the sigmoidicity of the curve.

A

Negative

89
Q

In Michaelis-Menten kinetics, positive modulator shift the v versus [substrate] plots toward the ___ plots

A

Hyperbolic

90
Q

In the presence of a positive modulator, 1/2vmax can be reached at a (higher/lower) substrate concentration than is required in the absence of the positive modulator.

A

Lower

91
Q

True or False

Large changes in allosteric-controlled enzyme activity are effected by small changes in substrate concentration.

A

True

92
Q

True or False
It is also possible to “turn an enzyme of” with small amounts of a negative allosteric effector by having the apparent Km shifted to values above the in vivo level of substrat.

A

True

93
Q

Model of ES complex

Restrictive, most of the nomenclature associated with allosterism and cooperativity arose from it.

A

Concerted model

94
Q

Model of ES complex
Proposes that ligand binding induces a conformational change in a protomer
Corresponding conformational change is then partially induced in an adjacent protomer contiguous with protomer containing the bound ligand

A

Sequential induced-fit model

Enzyme (2 decks)

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