Question 1

An enzyme catalyzes the removal of an amino group from one substrate and its addition to another compound.To what class of enzymes does it belong?

Accepted Answer

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

Question 2

To which class of enzymes would you assign an enzyme that carries out the dehydrogenation of its substrate?

Accepted Answer

A) oxidoreductases 
B) transferases 
C) lyases 
D) hydrolases 
E) All of the choices are correct. 
A) oxidoreductases 
B) transferases 
C) lyases 
D) hydrolases 
E) All of the choices are correct.

Question 3

In 1956,Christian de Duve discovered organelles in the cytoplasm of certain cells that have hydrolytic enzymes that destroy bacteria and viruses.What are these organelles called?

Accepted Answer

A) lysosomes 
B) mitochondria 
C) endosomes 
D) ribosomes 
E) nucleosomes 
A) lysosomes 
B) mitochondria 
C) endosomes 
D) ribosomes 
E) nucleosomes

Question 4

The enzyme hexokinase catalyzes the phosphorylation of glucose according to the reaction shown below.Glucosamine is a competitive inhibitor of hexokinase.Which of the following best describes the inhibition by glucosamine?

Accepted Answer

A) Glucosamine stabilizes the active site of the enzyme,preventing glucose-6-phosphate from being released. 
B) Glucosamine reacts with glucose,preventing it from binding to the active site of the enzyme. 
C) Glucosamine binds to the active site of the enzyme,preventing glucose from binding. 
D) Glucosamine binds to the surface of the enzyme,causing a change in the shape of both the enzyme and the active site,preventing glucose from binding. 
E) Glucosamine reacts with glucose-6-phosphate,preventing it from being released from the active site. 
A) Glucosamine stabilizes the active site of the enzyme,preventing glucose-6-phosphate from being released. 
B) Glucosamine reacts with glucose,preventing it from binding to the active site of the enzyme. 
C) Glucosamine binds to the active site of the enzyme,preventing glucose from binding. 
D) Glucosamine binds to the surface of the enzyme,causing a change in the shape of both the enzyme and the active site,preventing glucose from binding. 
E) Glucosamine reacts with glucose-6-phosphate,preventing it from being released from the active site.

Question 5

The presence of an enzyme catalyst will affect the time taken for a reaction to reach equilibrium.

Accepted Answer

A) True 
 B)False

Question 6

What is the classification of an enzyme that catalyzes the joining of two molecules?

Accepted Answer

A) kinase 
B) ligase 
C) oxidoreductase 
D) transferase 
E) hydrolase 
A) kinase 
B) ligase 
C) oxidoreductase 
D) transferase 
E) hydrolase

Question 7

What is an allosteric enzyme?

Accepted Answer

A) an enzyme whose activity is regulated by the binding of a small effector molecule 
B) the inactive form of an enzyme 
C) an enzyme that has become denatured and can no longer catalyze reactions 
D) an enzyme that is bound to an inhibitor molecule 
E) an enzyme that catalyzes reactions in plants and animals,but not humans 
A) an enzyme whose activity is regulated by the binding of a small effector molecule 
B) the inactive form of an enzyme 
C) an enzyme that has become denatured and can no longer catalyze reactions 
D) an enzyme that is bound to an inhibitor molecule 
E) an enzyme that catalyzes reactions in plants and animals,but not humans

Question 8

Acetylcholine is a neurotransmitter that transmits a signal from a nerve cell to a muscle cell,causing the muscle to contract.How is the neurotransmitter inactivated so that the muscle can relax?

Accepted Answer

A) It is denatured by the local pH and loses its active conformation. 
B) It is hydrolyzed by the enzyme acetylcholinesterase. 
C) It is taken up and stored by the muscle cells. 
D) It is dissolved in the blood and is transported through the circulatory system. 
E) All of the choices are correct. 
A) It is denatured by the local pH and loses its active conformation. 
B) It is hydrolyzed by the enzyme acetylcholinesterase. 
C) It is taken up and stored by the muscle cells. 
D) It is dissolved in the blood and is transported through the circulatory system. 
E) All of the choices are correct.

Question 9

Proteolytic digestive enzymes are often produced in an inactive form.What is the name that refers to the inactive form of an enzyme?

Accepted Answer

A) isozyme 
B) zwitterion 
C) proenzyme 
D) inhibitor 
E) allele 
A) isozyme 
B) zwitterion 
C) proenzyme 
D) inhibitor 
E) allele

Question 10

The diagram below shows the energy pathway of an uncatalyzed reaction.How does the energy diagram change when an enzyme is used in the same reaction?

Accepted Answer

A) The energy of the products decreases. 
B) The energy of the reactants increases. 
C) The energy of the reactants decreases. 
D) The activation energy decreases. 
E) The energy of the reactants becomes equal to the energy of the products. 
A) The energy of the products decreases. 
B) The energy of the reactants increases. 
C) The energy of the reactants decreases. 
D) The activation energy decreases. 
E) The energy of the reactants becomes equal to the energy of the products.

Question 11

To which class of enzymes does an enzyme belong if it catalyzes the rearrangement of functional groups within a molecule?

Accepted Answer

A) oxidoreductases 
B) lyases 
C) ligases 
D) isomerases 
E) lyases and ligases are correct. 
A) oxidoreductases 
B) lyases 
C) ligases 
D) isomerases 
E) lyases and ligases are correct.

Question 12

Which of the following best describes the type of binding between an irreversible inhibitor and an enzyme?

Accepted Answer

A) weak 
B) non-covalent 
C) hydrogen bonding 
D) hydrophobic interactions 
E) very tight 
A) weak 
B) non-covalent 
C) hydrogen bonding 
D) hydrophobic interactions 
E) very tight

Question 13

What type of specificity is displayed by an enzyme that is able to catalyze a reaction of D-glucose,but not L-glucose?

Accepted Answer

A) absolute specificity 
B) stereospecificity 
C) group specificity 
D) optical specificity 
E) sugar specificity 
A) absolute specificity 
B) stereospecificity 
C) group specificity 
D) optical specificity 
E) sugar specificity

Question 14

Trypsin is a protease enzyme that cleaves peptide bonds on the carbonyl side of basic amino acids.Which labeled bond(s)in the peptide below would be cleaved by trypsin?

Accepted Answer

A) A 
B) B 
C) C 
D) D 
E) A,C,and D 
A) A 
B) B 
C) C 
D) D 
E) A,C,and D

Question 15

Hydrochloric acid in the stomach is partially responsible for activating pepsinogen.

Accepted Answer

A) True 
 B)False

Question 16

Of the following types of molecular interactions,which is NOT likely to be involved in the binding of an enzyme to a substrate?

Accepted Answer

A) covalent linkages 
B) hydrogen bonds 
C) van der Waals attractions 
D) polar-polar attractions 
E) ionic attractions 
A) covalent linkages 
B) hydrogen bonds 
C) van der Waals attractions 
D) polar-polar attractions 
E) ionic attractions

Question 17

Arsenic is an example of an irreversible enzyme inhibitor.

Accepted Answer

A) True 
 B)False

Question 18

Which of the following is true for an enzyme catalyzed reaction?

Accepted Answer

A) The rate of the reaction will increase indefinitely with an increase in the substrate concentration. 
B) The rate of the reaction will increase with an increase in the substrate concentration until it reaches a maximum rate. 
C) The rate of the reaction will decrease as the substrate concentration increases. 
D) The rate of the reaction is unaffected by substrate concentration. 
E) The rate of the reaction decreases as the amount of enzyme available increases. 
A) The rate of the reaction will increase indefinitely with an increase in the substrate concentration. 
B) The rate of the reaction will increase with an increase in the substrate concentration until it reaches a maximum rate. 
C) The rate of the reaction will decrease as the substrate concentration increases. 
D) The rate of the reaction is unaffected by substrate concentration. 
E) The rate of the reaction decreases as the amount of enzyme available increases.

Question 19

A holoenzyme is a functional enzyme composed of what two parts?

Accepted Answer

A) apoenzyme and cofactor 
B) amino acid and NAD+ 
C) substrate and catalyst 
D) transferase and ligase 
E) substrate and inhibitor 
A) apoenzyme and cofactor 
B) amino acid and NAD+ 
C) substrate and catalyst 
D) transferase and ligase 
E) substrate and inhibitor

Question 20

For enzyme-catalyzed reactions,what happens as the concentration of the substrate is increased?

Accepted Answer

A) The rate continues to increase as substrate concentration increases. 
B) The rate increases until it reaches a maximum,constant value. 
C) The rate increases until it reaches a maximum,then the rate decreases. 
D) The rate decreases with increasing concentration of the substrate. 
E) The rate decreases until it reaches a minimum,constant value. 
A) The rate continues to increase as substrate concentration increases. 
B) The rate increases until it reaches a maximum,constant value. 
C) The rate increases until it reaches a maximum,then the rate decreases. 
D) The rate decreases with increasing concentration of the substrate. 
E) The rate decreases until it reaches a minimum,constant value.

Exam 19: Enzymes

An enzyme catalyzes the removal of an amino group from one substrate and its addition to another compound.To what class of enzymes does it belong?

To which class of enzymes would you assign an enzyme that carries out the dehydrogenation of its substrate?

In 1956,Christian de Duve discovered organelles in the cytoplasm of certain cells that have hydrolytic enzymes that destroy bacteria and viruses.What are these organelles called?

The enzyme hexokinase catalyzes the phosphorylation of glucose according to the reaction shown below.Glucosamine is a competitive inhibitor of hexokinase.Which of the following best describes the inhibition by glucosamine?

The presence of an enzyme catalyst will affect the time taken for a reaction to reach equilibrium.

What is the classification of an enzyme that catalyzes the joining of two molecules?

What is an allosteric enzyme?

Acetylcholine is a neurotransmitter that transmits a signal from a nerve cell to a muscle cell,causing the muscle to contract.How is the neurotransmitter inactivated so that the muscle can relax?

Proteolytic digestive enzymes are often produced in an inactive form.What is the name that refers to the inactive form of an enzyme?

The diagram below shows the energy pathway of an uncatalyzed reaction.How does the energy diagram change when an enzyme is used in the same reaction?

To which class of enzymes does an enzyme belong if it catalyzes the rearrangement of functional groups within a molecule?

Which of the following best describes the type of binding between an irreversible inhibitor and an enzyme?

What type of specificity is displayed by an enzyme that is able to catalyze a reaction of D-glucose,but not L-glucose?

Trypsin is a protease enzyme that cleaves peptide bonds on the carbonyl side of basic amino acids.Which labeled bond(s)in the peptide below would be cleaved by trypsin?

Hydrochloric acid in the stomach is partially responsible for activating pepsinogen.

Of the following types of molecular interactions,which is NOT likely to be involved in the binding of an enzyme to a substrate?

Arsenic is an example of an irreversible enzyme inhibitor.

Which of the following is true for an enzyme catalyzed reaction?

A holoenzyme is a functional enzyme composed of what two parts?

For enzyme-catalyzed reactions,what happens as the concentration of the substrate is increased?

Chemistry - Methods and Measurement

The Structure of the Atom and the Periodic Table

Structure and Properties of Ionic and Covalent Compounds

Calculations, chemical Changes, and the Chemical Equation

States of Matter: Gases, liquids, and Solids

Solutions

Energy,rate and Equilibrium

Acids and Bases

The Nucleus, radioactivity, and Nuclear Medicine

An Introduction to Organic Chemistry

The Unsaturated Hydrocarbons: Alkenes, alkynes, and Aromatics

Alcohols, phenols, thiols, and Ethers

Aldehydes and Ketones

Carboxylic Acids and Carboxylic Acid Derivatives

Amines and Amides

Carbohydrates

Lipids and Their Functions in Biochemical Systems

Protein Structure and Function

Introduction to Molecular Genetics

Carbohydrate Metabolism

Aerobic Respiration and Energy Production

Fatty Acid Metabolism

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