Devlin

Question 1

Specialized proteins that function in the acceleration of chemical reactions

Answer 1

Enzymes

Question 2

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

Answer 2

Catalyst

Question 3

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

Answer 3

True. (See Devlin)

Question 4

True/False

Enzymes change the equilibrium constant of the reaction.

Answer 4

False.

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

Question 5

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

Answer 5

Energy of activation

Question 6

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

Answer 6

Apoenzyme

Question 7

Catalytically inactive part of the enzyme

Answer 7

Apoenzyme

Question 8

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

Answer 8

Cofactor

Question 9

Similar to a cofactor but is tightly bound to an apoenzyme

Answer 9

Prostethetic group

Question 10

Active enzyme

Addition of a cofactor or prosthetic group to the apoprotein

Answer 10

Holoenzyme

Question 11

Molecule acted upon by the enzyme to form product

Answer 11

Substrate

Question 12

True or False

Enzymes have a great deal of specificity

Answer 12

True. (Devlin)

Question 13

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

Answer 13

Substrate-binding site

Question 14

True or False

Some enzymes have broad specificity.

Answer 14

True.

Glucose, mannose and fructose are phosphorylated by hexokinase.

Question 15

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

Answer 15

Active site

Question 16

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

Answer 16

Isoenzyme

Question 17

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.

Answer 17

Allosteric site

Question 18

True or False

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

Answer 18

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

Question 19

6 major classification of enzymes

Answer 19

Oxidoreductases
Transferases
Hydrolases
Isomerases
Ligases
Lyases
(Remember ILLHOT)

Question 20

Catalyze oxidation-reduction reactions

Answer 20

Oxidoreductases

Question 21

Subclasses of oxidoreductase

Answer 21

Dehydrogenase
Oxidase
Oxygenase
Reductase
Peroxidase
Catalase
Hyroxylase

Question 22

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

Answer 22

Oxidases

Question 23

Catalyze the incorporation of oxygen into a substrate

Answer 23

Oxygenases

Question 24

Utilize hydrogen peroxide rather than oxygen as oxidant

Answer 24

Peroxidase

Question 25

Unique in that hydrogen peroxide serves as both and acceptor

Answer 25

Catalase | Catalase functions in the cell to detoxify hydrogen peroxide

Question 26

Transfer functional groups between donors and acceptors

Answer 26

Transferase

Question 27

Subclasses of transferases

Answer 27

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

Question 28

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

Answer 28

Kinases

Question 29

``` 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 ```

Answer 29

Hydrolases

Question 30

Proteolytic enzymes are a special class of hydroxylases

Answer 30

Peptidases

Question 31

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

Answer 31

Lyases

Question 32

Subclasses of hydrolases

Answer 32

``` Esterase Glycosidases Peptidases Phosphatases Thiolases Phospholipidases Amidases Deaminases Ribonucleases ```

Question 33

Subclasses of lyases

Answer 33

``` Decarboxylases Aldolases Hydratases Dehydratases Synthases ```

Question 34

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

Answer 34

Decarboxylases

Question 35

Remove water in a dehydration reaction

Answer 35

Dehydratases

Question 36

Catalyze isomerizations of several types

Answer 36

Isomerases

Question 37

Subclasses of isomerases

Answer 37

Racemaces Epimerases Isomerases Mutases (not all)

Question 38

Involve intramolecular transfer of a group such as a phosphoryl

Answer 38

Mutase

Question 39

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

Answer 39

Ligases

Question 40

Subclasses of ligases

Answer 40

Sythetases | Carboxylases

Question 41

True or false | Velocity of an enzyme is dependent on both substrate and enzyme concentrations

Answer 41

True

Question 42

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

Answer 42

Steady state

Question 43

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.

Answer 43

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

Question 44

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.

Answer 44

Maximal

Question 45

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.

Answer 45

True.

Question 46

True or False. | pH and temperature have no effect in the constants Vmax and Km.

Answer 46

False.

Question 47

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

Answer 47

Lineweaver-Burk or double-reciprocal plot.

Question 48

True or False | An enzyme can only catalyze forward direction of a reversible reaction.

Answer 48

False. | Enzyme can catalyze the forward and reverse reactions.

Question 49

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.

Answer 49

True

Question 50

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

Answer 50

Rate of product removal.

Question 51

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

Answer 51

Product inhibition

Question 52

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

Answer 52

Product inhibition.

Question 53

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.

Answer 53

True

Question 54

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

Answer 54

True

Question 55

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

Answer 55

ATP

Question 56

FAD, FMN, NAD+, NADP+

Answer 56

Coenzymes

Question 57

3 major classes of inhibitors

Answer 57

Competitive Noncompetitive Uncompetitive

Question 58

Inhibitors whose action can be reversed by increasing amounts of substrate

Answer 58

Competitive inhibitors

Question 59

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

Answer 59

Substrate-binding site

Question 60

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

Answer 60

Remains constant; changes

Question 61

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.

Answer 61

True

Question 62

Binds at a site other than the substrate-binding site. | Not reversed by increasing concentration of substrate

Answer 62

Noncompetitive inhibitors

Question 63

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

Answer 63

Changes; remains constant

Question 64

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

Answer 64

Noncompetitive inhibitor

Question 65

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

Answer 65

Uncompetitive inhibitor

Question 66

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

Answer 66

Changes; changes

Question 67

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

Answer 67

Uncompetitive inhibitor

Question 68

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

Answer 68

Competitive inhibitor

Question 69

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

Answer 69

Noncompetitive inhibitor

Question 70

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

Answer 70

Allosteric site

Question 71

Ligands that bind at the allosteric site are called ___

Answer 71

Allosteric effectors

Question 72

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

Answer 72

Conformational change

Question 73

Increase the enzyme affinity for substrate or other ligand

Answer 73

Positive allosteric effectors

Question 74

Decrease the enzyme affinity for substrate or other ligand

Answer 74

Negative allosteric effectors

Question 75

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

Answer 75

activator site; inhibitory site

Question 76

Allosteric enzyme exhibits ____ kinetics

Answer 76

Sigmoidal

Question 77

Any molecule that is bound to a macromolecule | Can be activators, inhibitors or even the substrate of enzymes

Answer 77

Ligand

Question 78

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

Answer 78

Effectors Modifiers Modulators

Question 79

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

Answer 79

Rate-determining

Question 80

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

Answer 80

Km and Vmax

Question 81

Effector alters the Km but not Vmax

Answer 81

K class

Question 82

Effector alters the Vmax but not Km

Answer 82

V class

Question 83

Class of allosteric enzymes | Noncompetitive inhibitors

Answer 83

V class

Question 84

Class of allosteric enzymes | Gives double-reciprocal plots like those of competitive inhibitors

Answer 84

K class

Question 85

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

Answer 85

K class

Question 86

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

Answer 86

V class

Question 87

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

Answer 87

S-shape

Question 88

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

Answer 88

Negative

Question 89

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

Answer 89

Hyperbolic

Question 90

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.

Answer 90

Lower

Question 91

True or False | Large changes in allosteric-controlled enzyme activity are effected by small changes in substrate concentration.

Answer 91

True

Question 92

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.

Answer 92

True

Question 93

Model of ES complex | Restrictive, most of the nomenclature associated with allosterism and cooperativity arose from it.

Answer 93

Concerted model

Question 94

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

Answer 94

Sequential induced-fit model