Harpers

Question 1

Biologic polymers that catalyze the chemical reactions

Answer 1

Enzymes

Question 2

Characteristics of enzymes

Answer 2

Catalytic activity
Substrate specificity
Stereospecificity

Question 3

Enzymes are classified by reaction type. Name the six classes of enzymes.

Answer 3

Oxidoreductases
Transferases
Hydrolases
Lyases
Isomerases
Ligases

Question 4

Naming enzymes may use modifiers to indicate the:

Answer 4

Substrate
Source of the enzymes
Regulation
Feature of its mechanism of action

Question 5

Enzymes that catalyze oxidations and reductions

Answer 5

Oxidoreductases

Question 6

Enzymes that catalyze transfer of moieties such as glycosyl, methyl, or phosphoryl groups

Answer 6

Transferases

Question 7

Enzymes that catalyze hydrolytic cleavage of C-C, C-O, C-N and other covalent bonds

Answer 7

Hydrolases

Question 8

Enzymes that catalyze cleavage of C-C, C-O, C-N and other covalent bonds by atom elimination, generating double bonds

Answer 8

Lyases

Question 9

Enzymes that catalyze geometric or structural changes within a molecule

Answer 9

Isomerases

Question 10

Enzymes that catalyze the joining together of two molecules in reactions coupled to the hydrolysis of ATP

Answer 10

Ligases

Question 11

Tightly and stably incorporated into a protein’s structure by covalent or noncovalent forces

Answer 11

Prosthetic group

Question 12

Examples are pyridoxal phosphate, flavin mononucleotide, flavin adenine dinucleotide, thiamin pyrophosphate, biotin, metal ions of cobalt, copper, magnesium, manganese, zinc

Answer 12

Prosthetic group

Question 13

Enzymes that contain tightly bound metal ions

Answer 13

Metalloenzymes

Question 14

Serve functions similar to those of prosthetic groups but bind in transient, dissociable manner either to the enzyme or to a substrate such as ATP

Answer 14

Cofactors

Question 15

Must be present in the medium surrounding the enzymes for catalysis to occur

Answer 15

Cofactors

Question 16

Enzymes that require a metal ion cofactor

Answer 16

Metal-activated enzyme

Question 17

Serve as recyclable shuttle-or group transfer agents-that transport many substrates from one point within the cell to another

Answer 17

Coenzymes

Question 18

Stabilize species such as hydrogen atoms or hydride ions that are too reactive to persist for any significant time period in the presence of the water or organic molecules that permeate the cell interior

Answer 18

Coenzymes

Question 19

Adaptor or handle that facilitates the recognition and binding of small chemical groups

Answer 19

Coenzymes

Question 20

Many coenzymes, cofactors and prosthetic groups are derivatives of ____

Answer 20

B vitamins

Question 21

Component of the redox coenzymes NAD and NADP

Answer 21

Nicotamide

Question 22

Component of the redox coenzymes FMN and FAD

Answer 22

Riboflavin

Question 23

Component of the acyl group carrier coenzyme A

Answer 23

Pantothenic acid

Question 24

Participates in decarboxylation of alpha-keto acids

Answer 24

Thiamin

Question 25

Function in one-carbon metabolism

Answer 25

Folic acid | Cobamide

Question 26

Enzymes and substrates interact to form ES complex whose thermal stability was ___ than that of enzyme itself

Answer 26

Greater

Question 27

Recognition site for binding substrates

Answer 27

Active site

Question 28

The higher the concentration of enzyme and substrate, the ___ frequently they will encounter one another, and the ___ will be the rate of the reaction.

Answer 28

More | Greater

Question 29

True or false In specific acid catalysis or specific base, the rate of reaction is sensitive to changes in the concentration of protons and dependent of the concentrations of other acids or bases present in the solution or at the active site.

Answer 29

False | Independent of the concentration of other acids or bases present in the solution

Question 30

Reactions whose rates are responsive to all the acids or bases present are said to be subject to ____

Answer 30

General acid/base catalysis

Question 31

Enzymes that catalyze ___ reactions that involve breaking a covalent bond typically bind their substrate in a conformation that is somewhat unfavorable for the bond that will undergo cleavage

Answer 31

Lytic

Question 32

A transient species that represents the transition state in the transformation of substrates to products

Answer 32

Transition state intermediates

Question 33

The process of ____ involves the formation of a covalent bond between the enzyme and one or more substrates

Answer 33

Covalent catalysis

Question 34

Covalent catalysis introduces a new reaction pathway whose activation energy is ___ than the reaction pathway in homogenous solution.

Answer 34

Lower

Question 35

When substrates approach and bind to an enzyme they induce a conformational change analogous to placing a hand into a glove

Answer 35

Induced fit model

Question 36

Exquisitely high specificity with which enzymes discriminate their substrates when forming an ES complex

Answer 36

Lock and key model

Question 37

Several physically distinct versions of a given enzyme, each of which catalyzes the same reaction

Answer 37

Isoenzyme

Question 38

Field of biochemistry concerned with the quantitative measurement of the rates of enzyme-catalyzed reactions and the systematic study of factors that affect these rates

Answer 38

Enzyme kinetics

Question 39

Anything that increases the frequency or energy of collision between substrates will ___ the rate of the reaction in which they participate

Answer 39

Increase

Question 40

Two factors that increase the frequency of collision between substrate

Answer 40

Temperature | Reactant concentration

Question 41

True or false | The presence of an enzyme alters the equilibrium constant of the reaction.

Answer 41

False It only lowers the activation energy. Since they emerge unchanged at the completion of the reaction, they do not affect the free energy for the overall reaction.

Question 42

In Michaelis-Menten equation, when [S] is considerably below Km, v is proportionate to k[S]. Therefore, the initial reaction velocity is ____ to [S].

Answer 42

Directly proportional

Question 43

In Michaelis-Menten equation, when [S] = Km, the initial velocity is ___.

Answer 43

Half-maximal

Question 44

The linear form of Michaelis-Menten equation

Answer 44

Double reciprocal plot | Lineweaver-Burk plot

Question 45

When further increases in substrate concentration do not further increase velocity, the enzyme is said to be ___ with the substrate

Answer 45

Saturated

Question 46

An exclusive property of multimeric enzymes that bind substrate at multiple sites

Answer 46

Cooperative behavior

Question 47

Inhibitor binds to the substrate-binding portion of the active site thereby blocking access by the substrate

Answer 47

Competitive inhibition

Question 48

Can be overcome by raising the concentration of substrate

Answer 48

Competitive inhibition

Question 49

Acts by decreasing the number of free enzyme molecules available to bind the substrate to form ES and thus eventually to form product

Answer 49

Competitive inhibitor

Question 50

Competitive inhibitor has no effect on ____ but raises the ___

Answer 50

Vmax | Km apparent

Question 51

Binding of the inhibitor does not affect binding of the substrate

Answer 51

Noncompetitive inhibition

Question 52

Formation of both EI and EIS complexes is possible

Answer 52

Noncompetitive inhibition

Question 53

True or false Competitive and noncompetitive inhibitors are reversible inhibitors, meaning the inhibitors form a dissociable, dynamic complex with the enzyme

Answer 53

True

Question 54

Modifications of enzyme involving making or breaking covalent bonds essential for substrate binding, catalysis or maintenance of the enzyme's conformation

Answer 54

Irreversible inhibitors