Deck 20: Enzymes

Question 1

Which of the following is a common function of many vitamins in the body?

A) substrates
B) apoenzymes
C) coenzymes
D) activators

Answer 1

coenzymes

Question 2

The theory that proposes a somewhat flexible enzyme conformation is the

A) lock-and-key theory.
B) induced-fit theory.
C) physically-fit theory.
D) expanding-fit theory.

Answer 2

induced-fit theory.

Question 3

Which statement does not apply to the lock and key theory?

A) It explains the functioning of enzymes.
B) It explains the need for a specific three dimensional structure found in proteins.
C) It explains the reason why a particular enzyme is involved with one substrate.
D) It explains why a substrate-enzyme complex is so difficult to separate.

Answer 3

It explains why a substrate-enzyme complex is so difficult to separate.

Question 4

The general term which refers to the catalytic ability of an enzyme is

A) enzyme turnover.
B) enzyme activity.
C) catalytic turnover.
D) catalytic speed.

Question 5

The substrate for the digestive enzyme named sucrase is _____ .

A) glucose
B) fructose
C) sucrose
D) more than one response is correct

Question 6

The catalytically inactive form of an enzyme is called a(n)_____ .

A) cofactor
B) proenzyme
C) apoenzyme
D) activator

Question 7

An enzyme is known to catalyze the conversion of proteins to amino acids.Which of the following would be a correct designation for the enzyme?

A) transferase
B) oxidoreductase
C) hydrolase
D) lyase

Question 8

The region of an enzyme where the substrate molecule fits is called the

A) active site.
B) substrate site.
C) substrate bond.
D) primary site.

Question 9

Which of the following terms can be used correctly to fill the blank in the following equation? apoenzyme + ____ $\rarr$ active enzyme

A) zymogen
B) cofactor
C) isozyme
D) substrate

Question 10

____ is an example of a cofactor required by an enzyme.

A) Acetyl coenzyme A
B) The ferrous (Fe²⁺)ion
C) Lipoamide
D) The sodium ion

Question 11

Which statement about enzymes is incorrect?

A) Enzymes can either speed up or slow down a chemical reaction.
B) Enzymes are not used up during the reaction in which they are involved.
C) Enzymes are proteins that are capable of reducing the activation energy.
D) There are enzymes that interact with one enantiomer,but not the other.

Question 12

Salivary amylase behaves as an enzyme only in the presence of chloride ions.Which of the following terms describes the function of the chloride ion?

A) coenzyme
B) zymogen
C) activator
D) active site

Question 13

If a metal ion is required to activate an enzyme,it would be considered a ____.

A) cofactor
B) protoenzyme
C) coenzyme
D) zymogen

Question 14

Which disease is attributed to the lack of enzyme?

A) hypertension
B) susceptibility to the cold viruses
C) Tay-Sachs disease
D) all of them

Question 15

Enzymes increase the rates of only certain reactions involving certain substances.This general characteristic is called ____.

A) selectivity
B) enzyme regulation
C) specificity
D) catalytic efficiency

Question 16

The number of substrate molecules acted upon per minute by one molecule of enzyme is referred to as the

A) optimum number.
B) optimum rate.
C) international unit.
D) turnover number.

Question 17

When enzyme activity is graphed versus the following,which graph is a straight line?

A) substrate concentration
B) enzyme concentration
C) pH
D) temperature

Question 18

Which of the following terms is a general definition of an enzyme?

A) catalyst
B) lipid
C) carbohydrate
D) activator

Question 19

____ would be considered as a common rate of chemical reaction measure per minute due to the presence of an enzyme.

A) 100
B) 1,000
C) 10,000
D) 100,000

Question 20

Which of the following enzyme properties is explained by the lock-and-key model?

A) specificity
B) high turnover rate
C) high molecular weight
D) susceptibility to denaturation

Question 21

A zymogen is correctly classified as a(n)

A) organic cofactor for an enzyme.
B) inorganic cofactor for an enzyme.
C) coenzyme.
D) inactive form of an enzyme.

Question 22

The optimum temperature for most enzymes is in the range of ____.

A) 25-40 ^$\circ$ C
B) 0-25 ^$\circ$ C
C) 50-70 ^$\circ$ C
D) 40-60 ^$\circ$ C

Question 23

An enzyme is operating at its optimum pH.If the pH were increased,how would the rate of the enzyme-catalyzed reaction change?

A) increase
B) decrease
C) could increase or decrease
D) would not change

Question 24

Enzymes which are affected by the binding of modulators are called

A) induced enzymes.
B) proenzymes.
C) allosteric enzymes.
D) controlled enzymes.

Question 25

Heavy metal ions are believed to act as ____ inhibitors.

A) reversible
B) irreversible
C) competitive
D) noncompetitive

Question 26

An enzyme useful in diagnosing leukemia is _____ .

A) CK
B) acid phosphatase
C) lysozyme
D) LDH

Question 27

The toxicity of cyanide is due to its affinity for the

A) (-SH groups of enzymes.)
B) carboxyl groups of active sites.
C) iron atoms of cytochrome oxidase.
D) amino groups of hemoglobin.

Question 28

What is the general effect of increasing the substrate concentration in a reaction?

A) The rate of the reaction will increase significantly.
B) The rate of the reaction will increase eventually leveling off.
C) The rate of the reaction will decrease significantly.
D) The substrate concentration cannot be changed in any chemical reaction.

Question 29

What is the reason for performing an enzyme assay?

A) to determine the number of enzyme molecules per liter
B) to determine the number of enzyme molecules per mL
C) to determine the activity of an enzyme
D) to determine the number of enzymes present

Question 30

An enzyme valuable in diagnosing heart attacks is _____ .

A) LDH
B) GPT
C) lipase
D) lysozyme

Question 31

What is the function of an inhibitor?

A) slow down the rate of reaction
B) inhibit the effect of temperature and pH changes on enzyme activity
C) inhibit substrate effects on other chemicals in the reaction environment
D) slow down the interaction between the solvent and the substrate

Question 32

Substances that can bind to an enzyme and increase its activity are called

A) positive modulators.
B) negative modulators.
C) allosteric regulators.
D) positive regulators.

Question 33

Which of the following enzyme types have proven especially useful in diagnostic medicine?

A) allosteric enzyme
B) proenzymes
C) isoenzymes
D) induced enzymes

Question 34

The conditions required for maximum enzyme function are called

A) room conditions.
B) standard conditions.
C) optimum conditions.
D) low pressure,high temperature.

Question 35

Which of the following is true of a noncompetitive inhibitor?

A) resembles the substrate
B) binds at a site other than the active site
C) can be reversed by adding more substrate
D) more than one response is correct

Question 36

Sulfa drugs prevent bacterial growth by acting as ____ inhibitors.

A) competitive
B) noncompetitive
C) irreversible
D) more than one response is correct

Question 37

Under saturation conditions,an enzyme-catalyzed reaction had a velocity V.Which of the following would increase the rate of the reaction?

A) a decrease in the substrate concentration
B) an increase in the substrate concentration
C) a decrease in the enzyme concentration
D) an increase in the enzyme concentration

Question 38

Which modification of the reaction environment will increase the rate of reaction in which an enzyme participates?

A) increase the temperature to the boiling point of water
B) increase the concentration of the product to saturation
C) increase the concentration of the enzyme
D) increase the amount of water in the solution

Question 39

The use of antibiotic creams and ointments should be restricted.Why?

A) The excessive use will affect the flexibility of the skin in the immediate area.
B) There is a possibility that the antibiotic will cause the skin to become dry.
C) There is a possibility that antibiotic immune strains of bacteria will develop.
D) There is more than one correct response.

Question 40

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

A) allosteric production.
B) enzyme induction.
C) feedback control.
D) biofeedback.

Question 41

How does a zymogen differ from an apoenzyme?

A) An apoenzyme is deactivated by a cofactor.
B) A zymogen is initially lacking an active site.
C) A zymogen is activated by removing part of its structure.
D) An apoenzyme is produced from a holoenzyme + coenzyme

Question 42

Which of the following accurately describes how an enzyme functions?

A) Reduces the enthalpy difference for the reactants and products.
B) Allows for the exothermic reaction of materials that are usually endothermic.
C) Changes the reaction mechanism,effectively reducing the activation energy.
D) Shifts the equilibrium for the reaction.

Question 43

The following represents the results of an experiment on a metabolic enzyme.What is the optimum pH of this enzyme?

A) 3.0
B) 5.5
C) 6.5
D) 9.5

Question 44

Enzyme concentration has what effect on the rate of an enzyme catalyzed reaction?

A) increases
B) decreases
C) no effect
D) increases until reaching a maximum

Question 45

Which of the following disorders results from a deficiency of the enzyme tyroinase?

A) Albinism
B) Galactosemia
C) Phenylketonuria
D) Homocystinuria

Question 46

A type of enzyme regulation,where a product acts as an inhibitor molecule,is called ___ inhibition.

A) feedback
B) end product
C) competitive
D) zymogenic

Question 47

In an enzyme assay,4.5 $\mu$ mol of substrate was consumed in 3.166 min.What is the enzyme activity expressed in IU?

A) 4.5 IU
B) 14 IU
C) 0.70 IU
D) 1.4 IU

Question 48

In the diagram,which number would represent V_max?

A) 1
B) 2
C) 3
D) either 2 or 3

Question 49

Chymotrypsin,an enzyme that cleaves peptide linkages,would be classified as a(n)_____ .

A) hydrolase
B) oxioreductase
C) isomerase
D) transferase

Question 50

What type of enzyme would catalyze the following reaction?

A) ligase
B) oxidoreductase
C) isomerase
D) transferase

Question 51

Which of the following describes the significance of the term V_max ?

A) how rapidly a substrate molecule can travel to an enzyme
B) the maximum rate that an enzyme can process substrate species
C) the velocity at which the enzyme and substrate must collide for activation
D) the maximum speed at which product molecules leave the binding site.

Question 52

Consider the following reaction.
The enzyme that would be placed over the arrow is a _____ .

A) ligase
B) lyase
C) hydrolase
D) transferase

Question 53

Which of the following is (are)active enzyme(s)?

A) pepsinogen
B) proelastase
C) trypsin
D) all are active enzymes

Question 54

Which of the following is a (are)zymogen(s)?

A) pepsin
B) chymotrypsinogen
C) carboxypeptidase
D) all are zymogens

Question 55

A neighbor comes to you having just moments ago ingested an unknown amount of antifreeze.You are miles from the nearest hospital.Which of the following is your best course of action after calling 911?

A) To make their last moments as pleasant as possible.
B) Give them enough whiskey to nearly get them intoxicated.
C) Give them methanol to detoxify the antifreeze.
D) Do nothing because antifreeze is not toxic to people.

Question 56

Substrate concentration has what effect on the rate of an enzyme catalyzed reaction?

A) increases
B) decreases
C) no effect
D) increases until reaching a maximum

Question 57

The cyanide ion is very toxic to humans because it binds with iron (Fe³⁺)in what enzyme to form a stable complex that stops cellular respiration.

A) cytochrome reductase
B) cytochrome kinase
C) cytochrome oxidase
D) elastase

Question 58

The EC name of an enzyme is alanine transaminase.This indicates that

A) the substrate is alanine.
B) the functional group is an amine.
C) the type of reaction is a transfer.
D) All of the above.

Question 59

A substance that when added to a reaction causes the production of more product is called a _____ .

A) catalyst
B) substrate
C) inhibitor
D) none of the choices

Question 60

The enzyme model that accounts for molecule flexibility is

A) lock and key.
B) induced fit.
C) allosteric effects.
D) More than one answer is correct.

Question 61

The conversion of a zymogen into an enzyme usually involves another enzyme.

Question 62

Enzymes are proteins that speed up a chemical reaction;inhibitors slow down chemical reactions.

Question 63

Feedback inhibition is a type of allosteric regulation.

Question 64

Enzyme assays are reported in international units (IU).By the definition of an IU,the quantity of enzyme present is measured,not the chemical activity.

Question 65

Sulfanilamide prevents bacterial growth because it functions as a competitive inhibitor.

Question 66

Inhibition is the irreversible process by which enzymes are rendered nonfunctional.

Question 67

Cofactors and enzymes form a tightly bound complex without which enzymes will not function.

Question 68

Trypsin is an example of a proenzyme.

Question 69

The measurement of various enzymes in the blood have been found to be useful for diagnosing pathological conditions.Which of the following enzymes is used to detect bone disease?

A) creatine kinase
B) aspartate transaminase
C) lactate dehydrogenase
D) alkaline phosphatase

Question 70

Noncompetitive inhibitors bind strongly to the active site.

Question 71

Consider the following figure.The step labeled A is known to reduce the activity of Enzyme 1.This would be described as what type of enzyme regulation?

A) end product inhibition
B) feedback inhibition
C) allosteric inhibition
D) competitive inhibition

Question 72

Enzymes have specific temperature and pH ranges within which they function best.

Question 73

Noncompetitive inhibitors often resemble the natural substrate in structure.

Question 74

The lock-and-key theory is the explanation of how a coenzyme functions to modify the substrate which provides a specific product.

Question 75

Many drugs act as competitive inhibitors.

Question 76

Zymogen is another term for cofactor.

Question 77

An irreversible inhibitor usually forms a covalent bond with the enzyme.

Question 78

Enzymes,being proteins,are sensitive to the temperature and will be denatured by high temperatures.

Question 79

All enzymes catalyze specific reactions which makes it simpler to understand the chemistry of the living cell.

Question 80

Pepsin is named because it catalyzes a hydrolysis reaction,and the IEC uses "in" as the word ending to indicate hydrolysis reaction.