Chem, Ch 10 Enzymes, Exam 3

Front 1

The substance that undergoes a chemical change catalyzed by an enzyme.

Back 1

substrate

Front 2

The inactive precursor of an enzyme.

Back 2

zymogen

Front 3

A non protein molecule required by an enzyme for catalytic activity.

Back 3

cofactor

Front 4

A slightly different form of the same enzyme.

Back 4

isoenzyme

Front 5

The location on an enzyme where catalysis occurs.

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active site

Front 6

An enzyme with quaternary structure with specific modulator binding sites.

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allosteric enzyme

Front 7

An inactivated enzyme formed by the removal of the cofactor.

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apoenzyme

Front 8

As the concentration of ATP increases in a cell, it decreases the turnover number of citrate synthetase. In this case, ATP acts as a(n)

Back 8

modulator

Front 9

The graph above is a generalization. What factor could be changed (increased) to produce the graph above showing the rate of enzyme activity?

Back 9

enzyme concentration

Front 10

An enzyme-substrate solution at p H 1 shows no product formation. Slowly increasing the p H from p H 1 to p H 14 still does not show any sign of enzyme activity. This is most likely because

Back 10

the enzyme has been denatured

Front 11

What would be an appropriate name for an enzyme that catalyzes the hydrolysis of fumarate?

Back 11

fumarase

Front 12

Enzymes catalyze only certain reactions involving certain substances. This general characteristic is called. --BLANK.

Back 12

catalytic efficiency

Front 13

What best accounts for the fact that many enzymes only act as catalysts for one specific reaction?

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the lock-and-key theory

Front 14

The number of molecules of substrate acted upon by one enzyme molecule in one minute is called the

Back 14

turnover number

Front 15

What factor could be changed (increased) to produce the graph above showing the rate of enzyme activity?

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substrate concentration

Front 16

Heavy metal ions are believed to act as.---blank. inhibitors of enzymes.

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irreversible

Front 17

An enzyme was poisoned by an inhibitor, but increasing the concentration of the substrate was found to return most of the enzyme's function. This is an example of what specific type of enzyme inhibition?

Back 17

competitive

Front 18

Enzymes speed up chemical reactions by

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reducing activation energies

Front 19

An analysis of isoenzymes in blood serum can be used to

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diagnose disease

Front 20

With the exception of a few RNA molecules all enzymes are .---BLANK.

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globular proteins

Front 21

To what family of biomolecules does the majority of enzymes belong?

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proteins

Front 22

An enzyme is a biomolecule that catalyzes.---BLANK.

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chemical reactions

Front 23

Biomolecules which catalyze chemical reactions are called.---blank.

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enzymes

Front 24

Enzymes are well suited to their essential roles in living organisms in three major ways: They have enormous catalytic power, they are highly specific in the reactions they catalyze, and their activity as catalysts can be.---Blank.

Back 24

regulated

Front 25

Three important characteristics of enzymes are high catalytic power, specificity, and that their activity can be .---blank.

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regulated

Front 26

Enzymes are true catalysts that speed chemical reactions by lowering activation energies, allowing reactions to achieve .---blank. more rapidly

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equilibrium

Front 27

Enzymes speed up reactions by lowering .---blank.

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activation energies

Front 28

Enzymes are often quite specific in the type of reaction they catalyze and even the particular substance that will be involved in the reaction. This important characteristic is called .---blank.

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specificity

Front 29

What term is used to describe the characteristic that enzymes catalyze only certain reactions?

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specificity

Front 30

The catalyzing of the reaction of one and only one substance is called.---blank.

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absolute specificity

Front 31

The enzyme urease which acts upon only one substance is called?

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absolute specificity

Front 32

.---BLANK. is exhibited by enzymes catalyzing the reaction of structurally related substances.

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Relative specificity

Front 33

Proteases, enzymes which can hydrolyze substances belonging to the family of proteins, exhibit .---blank. specificity.

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relative

Front 34

Stereochemical specificity extends to .---blank.: D-amino acid oxidase will not catalyze the reactions of L-amino acids.

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enantiomers

Front 35

The characteristic of an enzyme that it catalyzes a reaction of only one or a pair of stereoisomers is called .---blank. specificity.

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sterochemical

Front 36

The earliest discovered enzymes were given names ending with .---blank. to indicate their protein composition. A systematic nomenclature system known as the International Enzyme Commission (IEC) system groups enzymes into six classes and assigns each enzyme a specific name.

Back 36

–in

Front 37

What name is given to the systematic nomenclature system for enzymes?

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International Enzyme Commission System

Front 38

How many major classes of enzymes are designated by the systematic nomenclature system?

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six

Front 39

Enzymes are assigned convenient common names with the ending .---blank.

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–ase

Front 40

A chemical substance can often be identified as an enzyme by the ending .---blank. in the name.

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-ase

Front 41

A .---blank. will remove hydrogens from a compound.

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dehydrogenase

Front 42

The substance that undergoes a chemical change catalyzed by an enzyme is called the .---blank.

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substrate

Front 43

The substance acted upon by the enzyme urease is .---blank.

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urea

Front 44

Some common names indicate both the substrate and type of .---blank.. For example, alcohol dehydrogenase specifies a dehydrogenation (removal of hydrogen) from an alcohol.

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reaction

Front 45

What is the substrate for the enzyme lactate dehydrogenase?

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lactate

Front 46

A number of hereditary diseases appear to result from the absence of enzymes or from the presence of altered enzymes. These diseases are often referred to as .---blank. of metabolism.

Back 46

inborn errors

Front 47

A disease in which a genetic change causes a deficiency of a particular enzyme is called an .---blank. error of metabolism.

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inborn

Front 48

Nonprotein molecules or ions, weakly bound to an enzyme, and yet required by an enzyme for catalytic activity are called .---blank..

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cofactors

Front 49

The enzyme carbonic anhydrase functions only when Zn2+ ion is present. Zn2+ ion is an example of an enzyme .---blank..

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cofactor

Front 50

A number of metal ions are required in our diet for good health because they are essential for proper enzyme function as .---blank.

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cofactors

Front 51

A number of minerals are important components in our diet because the metal ions serve as enzyme .---blank.

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cofactors

Front 52

When the cofactor is an organic substance, it is called a .---blank.

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coenzyme

Front 53

Because NAD+, a cofactor for the enzyme lactate dehydrogenase, is organic, it may also be referred to as a .---blank.

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coenzyme

Front 54

The protein portion of enzymes requiring a cofactor is called the apoenzyme. The combination of an apoenzyme and cofactor produces an.--blank.

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Apoenzyme + cofactor (coenzyme or inorganic ion) = active enzyme

Front 55

If an active enzyme is stripped of its cofactor, the protein portion remaining is called the .---blank.

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apoenzyme

Front 56

A number of coenzymes are formed in the body from vitamins. For example, the coenzyme NAD+ is formed from the vitamin precursor .---blank.

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nicotinamide

Front 57

What substances does the body use to synthesize cofactors?

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vitamins

Front 58

What substance is a precursor for NAD+?

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nicotinamide

Front 59

The region of an enzyme where the substrate and enzyme interact is called the .---blank.

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active site

Front 60

The location on an enzyme where a substrate is bound and catalysis occurs is called the .---blank.

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active site

Front 61

The complex formed when a substrate and an enzyme bond is called the enzyme – substrate (ES) complex . As the complex forms, the lock-and-key theory proposes that a specific substrate has a shape fitting that of the enzyme’s.---blank., as a key fits a lock.

Back 61

active site

Front 62

The combination formed when substrate and enzyme bond is called the enzyme – substrate .---blank.

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complex

Front 63

What theory proposes that only specific substrates “fit” a given enzyme and can form combinations with it?

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lock-and-key theory

Front 64

A modification of the lock-and-key theory known as the .---blank. proposes that enzymes have a somewhat flexible conformation that may adapt to incoming substrates

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fit theory

Front 65

What theory proposes that the conformation of an enzyme changes to accommodate an incoming substrate?

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induced-fit theory

Front 66

Enzyme activity refers in general to the.---blank. of an enzyme to increase the rate of a reaction.

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catalytic ability

Front 67

The rate at which an enzyme catalyzes a reaction is termed enzyme .---blank.

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activity

Front 68

The experiments which measure rates of enzyme-catalyzed reactions are called enzyme .---blank.

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assays

Front 69

The turnover number for an enzyme is the number of molecules of .---blank. acted upon by one molecule of enzyme per minute.

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substrate

Front 70

One molecule of carbonic anhydrase converts 36 million molecules of carbon dioxide to carbonic acid per minute. The number 36 million is known as the .---blank. number.

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turnover

Front 71

An .---blank. (IU) is a quantity of enzyme that catalyzes the conversion of 1 μ mol of substrate per minute.

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enzyme international unit

Front 72

An enzyme IU (international unit) is an amount of enzyme that converts one .---blank. of substrate per minute.

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μ mol

Front 73

Several factors affect the rate of enzyme-catalyzed reactions. When enzyme concentration is increased, the rate of a reaction .---blank. in a directly proportional way

Back 73

increases

Front 74

What type of line is produced when enzyme concentration is plotted versus reaction rate?

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straight

Front 75

When substrate concentration is increased, the reaction rate initially increases and then levels out at a maximum velocity (V max) as all the active sites become .---blank. with substrate

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saturated

Front 76

A maximum velocity is achieved by increasing substrate concentration until the enzyme is .---blank.

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saturated

Front 77

.---blank. have rates that increase with temperature, reach a maximum at the optimum temperature, and then decline as the enzyme is denatured. The optimum temperature usually falls in the range of 25-40oC.

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Enzyme-catalyzed reactions

Front 78

The temperature at which enzyme activity is highest is called the .---blank. temperature.

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optimum

Front 79

Enzymes are usually most effective in a narrow pH range and are less active at pH values lower or higher than this optimum p H. Many enzymes have an .---blank. pH near 7, the pH of most biological fluids. pH's above or below the optimum will denature the protein.

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optimum

Front 80

The pH at which enzyme activity is highest is called the .---blank. pH.

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optimum

Front 81

An enzyme .---blank. is any substance that can decrease the rate of an enzyme-catalyzed reaction.

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inhibitor

Front 82

A substance that decreases the activity of an enzyme is called an enzyme .---blank.

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inhibitor

Front 83

Enzyme inhibitors are classified into two categories: .---blank.

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reversible and irreversible.

Front 84

The two categories of enzyme inhibitors are reversible and .---blank.

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irreversible

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An .---blank. forms a covalent bond with the enzyme and renders it inactive.

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irreversible inhibitor

Front 86

Cyanide is an example of an .---blank. enzyme inhibitor.

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irreversible

Front 87

Cyanide is toxic because of its impact on the enzyme .---blank. oxidase.

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cytochrome

Front 88

Penicillins belong to a family of compounds that inhibit .---blank., an enzyme that is important in bacterial cell wall construction.

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transpeptidase

Front 89

Compounds, like penicillins, have the ability to prevent bacterial growth and can be referred to as .---blank..

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antibiotics

Front 90

Penicillin acts as an .---blank.inhibitor.

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irreversible

Front 91

A reversible inhibitor reversibly binds to an enzyme. There are two types of reversible inhibitors: .---blank.

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competitive and noncompetitive

Front 92

The two categories of reversible inhibitors are competitive and .---blank..

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noncompetitive

Front 93

A .---blank. binds to the active site of an enzyme and thus “competes” with substrate molecules for the active site.

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competitive inhibitor

Front 94

An enzyme inhibitor that competes with substrate for binding at the active site is referred to as a .---blank.inhibitor.

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competitive

Front 95

Sulfa drugs are examples of .---blank. enzyme inhibitors.

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competitive

Front 96

.---blank. can be reversed by increasing the concentration of substrate. The competition between inhibitor and substrate is won by whichever molecular species is in greater concentration.

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Competitive inhibition

Front 97

The effect of a competitive inhibitor can be reversed by adding .---blank. to the reaction.

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substrate

Front 98

A .---blank. bears no resemblance to the normal substrate and binds reversibly to the surface of an enzyme at a site other than the active site

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noncompetitive inhibitor

Front 99

If a reversible inhibitor binds to an enzyme at a location other than the active site, is it a competitive or noncompetitive inhibitor?

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noncompetitive

Front 100

Unlike competitive inhibition, noncompetitive inhibition cannot be .---blank.by the addition of more substrate.

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reversed

Front 101

Is competitive or noncompetitive enzyme inhibition affected by increasing substrate concentration?

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competitive

Front 102

A common mechanism for regulating enzyme activity is the synthesis of enzymes in the form of inactive precursors called .---blank. or .---blank.. When the active enzyme is needed, a stored zymogen is released and activated at the location of the reaction.

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zymogens

proenzymes

Front 103

The inactive precursor of an enzyme is called a ________.

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zymogen or proenzyme

Front 104

A second method of enzyme regulation involves modulators, substances that bind to an enzyme at a location other than the active site; they may .---blank.the activity (activators) or .---blank.the activity (noncompetitive inhibitors).

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increase

decrease

Front 105

Substances that can bind to an enzyme and increase or decrease the activity are called .---blank..

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modulators

Front 106

Modulators which increase the activity of an enzyme are called .---blank..

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activators

Front 107

Enzymes that have a quaternary protein structure with distinctive binding sites for modulators are referred to as .---blank. enzymes.

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allosteric

Front 108

An enzyme whose activity is regulated by the binding of modulators is called an .---blank. enzyme.

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allosteric

Front 109

The type of allosteric regulation in which the enzyme that catalyzes the first step of a series of reactions is inhibited by the final product is called .---blank..

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feedback inhibition

Front 110

A process in which the end product of a sequence of enzyme-catalyzed reactions inhibits an earlier step in the process is called .---blank. inhibition.

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feedback

Front 111

A third method of controlling the level of enzyme activity involves enzyme .---blank., the synthesis of enzymes in response to a temporary need of the cell.

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induction

Front 112

The synthesis of an enzyme in response to a cellular need is called enzyme .---blank..

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induction

Front 113

Changes in blood serum concentrations of specific enzymes can be used clinically to detect cell damage and even to suggest the site of the damage. .---blank., slightly different forms of the same enzyme produced by different tissues, are particularly useful in clinical diagnosis.

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Isoenzymes

Front 114

What name is given to slightly different forms of the same enzyme produced by different tissues?

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isoenzyme

Front 115

Lactate dehydrogenase (LDH) and creatine kinase (CK) are two enzymes which exist in .---blank. Because of the wide range of tissue distribution of LDH isoenzymes, serum levels of LDH are used in the diagnosis of a number of diseases.

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multiple forms.

Front 116

Two examples of isoenzymes are CK and .---blank..

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LDH

Front 117

An assay for the isoenzyme .---blank. makes a good initial diagnostic test because of the enzyme's wide distribution.

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LDH

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The enzyme acid phosphatase is useful in diagnosing cancer of the .---blank..

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prostate

Front 119

The pathological condition of hepatitis may be diagnosed using an assay for alanine .---blank..

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transaminase