Question 1

Binding of a negative effector converts an active site on an enzyme into the active configuration.

Accepted Answer

A) True 
 B)False  False

Question 2

Lactase is an enzyme that catalyzes the following reaction.Which statement describing this reaction is FALSE?

Accepted Answer

A) Lactose is the substrate in this reaction. 
B) Glucose is a product in this reaction. 
C) Galactose is a cofactor in this reaction. 
D) This reaction occurs in the active site of lactase. 
E) Lactase is a hydrolase enzyme. 
A) Lactose is the substrate in this reaction. 
B) Glucose is a product in this reaction. 
C) Galactose is a cofactor in this reaction. 
D) This reaction occurs in the active site of lactase. 
E) Lactase is a hydrolase enzyme. C

Question 3

The rates of enzyme-catalyzed reactions increase with increasing pH.

Accepted Answer

A) True 
 B)False  False

Question 4

Which of the following describes how an enzyme can affect the transition state in an enzyme-catalyzed reaction?

Accepted Answer

A) modifying the local pH by accepting or donating H+ ions 
B) placing stress on a bond in the substrate,making it easier to break 
C) bringing two reactants together in close proximity and in a suitable orientation for reaction 
D) None of the choices are correct. 
E) All of the choices are correct. 
A) modifying the local pH by accepting or donating H+ ions 
B) placing stress on a bond in the substrate,making it easier to break 
C) bringing two reactants together in close proximity and in a suitable orientation for reaction 
D) None of the choices are correct. 
E) All of the choices are correct.

Question 5

The penicillin class of antibiotics is inhibitors of an enzyme responsible for the formation of bacterial cell walls.The penicillin covalently binds to a serine residue in the active site of the enzyme,as depicted below.What type of bond is formed between the penicillin and the active site?

Accepted Answer

A) hydrogen bond 
B) ionic bond 
C) glycosidic linkage 
D) ester bond 
E) acetal bond 
A) hydrogen bond 
B) ionic bond 
C) glycosidic linkage 
D) ester bond 
E) acetal bond

Question 6

Carboxypetidase A is a highly folded,globular protein that functions as a protease enzyme.Which of the following is a likely assumption about the amino acid residues that exist on the exterior of this folded protein?

Accepted Answer

A) The majority of these amino acids have disulfide bonds between cysteine residues. 
B) The majority of these amino acids are hydrophilic in nature. 
C) The majority of these residues are glycine. 
D) None of these residues is serine. 
E) The majority of these residues are nonpolar in nature. 
A) The majority of these amino acids have disulfide bonds between cysteine residues. 
B) The majority of these amino acids are hydrophilic in nature. 
C) The majority of these residues are glycine. 
D) None of these residues is serine. 
E) The majority of these residues are nonpolar in nature.

Question 7

What is the function of a lyase enzyme?

Accepted Answer

A) to catalyze redox reactions 
B) to catalyze the transfer of a functional group from one molecule to another 
C) to catalyze hydrolysis reactions 
D) to catalyze the addition of a group to a double bond or the removal of a group to form a double bond 
E) to catalyze the formation or cleavage of a C-C,C-S,C-O,or C-N bond 
A) to catalyze redox reactions 
B) to catalyze the transfer of a functional group from one molecule to another 
C) to catalyze hydrolysis reactions 
D) to catalyze the addition of a group to a double bond or the removal of a group to form a double bond 
E) to catalyze the formation or cleavage of a C-C,C-S,C-O,or C-N bond

Question 8

Which of the following will NOT destroy an enzyme by denaturation?

Accepted Answer

A) increase in temperature above 37°C (body temperature) 
B) decrease in temperature below 37°C 
C) significant increase in pH 
D) significant decrease in pH 
E) All of the choices will destroy an enzyme. 
A) increase in temperature above 37°C (body temperature) 
B) decrease in temperature below 37°C 
C) significant increase in pH 
D) significant decrease in pH 
E) All of the choices will destroy an enzyme.

Question 9

The arrival of a nerve impulse at the end plate of the nerve axon results in an influx of what ion?

Accepted Answer

A) calcium 
B) sodium 
C) potassium 
D) bicarbonate 
E) phosphate 
A) calcium 
B) sodium 
C) potassium 
D) bicarbonate 
E) phosphate

Question 10

Which of the following is NOT a class of enzymes?

Accepted Answer

A) isomerases 
B) transferases 
C) carnases 
D) lyases 
E) ligases 
A) isomerases 
B) transferases 
C) carnases 
D) lyases 
E) ligases

Question 11

The rate of an enzyme-catalyzed reaction initially increases with an increase in the substrate concentration,but eventually reaches a maximum value,even though the concentration of substrate continues to increase.Which of the following best explains why?

Accepted Answer

A) As substrate concentration increases,the substrates preferentially bind with each other instead of the active site of the enzyme,and no additional catalysis occurs. 
B) As substrate concentration increases,the active sites of all the enzyme molecules become occupied with substrate molecules,and no additional binding can occur. 
C) An increase in substrate concentration eventually increases the temperature of the reaction mixture,and the enzyme becomes denatured. 
D) An increase in substrate concentration allows for greater competition between substrate and inhibitor binding,and enzyme activity ceases. 
E) When substrate concentrations become too high,local variations of pH occur that cause the enzyme to become denatured. 
A) As substrate concentration increases,the substrates preferentially bind with each other instead of the active site of the enzyme,and no additional catalysis occurs. 
B) As substrate concentration increases,the active sites of all the enzyme molecules become occupied with substrate molecules,and no additional binding can occur. 
C) An increase in substrate concentration eventually increases the temperature of the reaction mixture,and the enzyme becomes denatured. 
D) An increase in substrate concentration allows for greater competition between substrate and inhibitor binding,and enzyme activity ceases. 
E) When substrate concentrations become too high,local variations of pH occur that cause the enzyme to become denatured.

Question 12

Sucrase is an example of an enzyme that displays absolute specificity.What does the term "absolute specificity" indicate about an enzyme?

Accepted Answer

A) It catalyzes the reaction of only a single substrate. 
B) It catalyzes the reaction of only one class of compounds. 
C) It catalyzes one type of reaction for the same class of compounds. 
D) It catalyzes the reaction of only a single enantiomer of a compound. 
E) It catalyzes the reaction of only a single type of bond. 
A) It catalyzes the reaction of only a single substrate. 
B) It catalyzes the reaction of only one class of compounds. 
C) It catalyzes one type of reaction for the same class of compounds. 
D) It catalyzes the reaction of only a single enantiomer of a compound. 
E) It catalyzes the reaction of only a single type of bond.

Question 13

What type of enzyme regulation occurs when the final product of a pathway shuts off the entire pathway for its own synthesis?

Accepted Answer

A) irreversible inhibition 
B) competitive inhibition 
C) feedback inhibition 
D) poisoning 
E) noncompetitive inhibition 
A) irreversible inhibition 
B) competitive inhibition 
C) feedback inhibition 
D) poisoning 
E) noncompetitive inhibition

Question 14

The enzyme acetylcholinesterase catalyzes the hydrolysis of acetylcholine.Which of the following is a product of this hydrolysis reaction?

Accepted Answer

A) 
  
B) 
  
C) 
  
D) 
  
E) 
  
A) 
  
B) 
  
C) 
  
D) 
  
E)

Question 15

At extremes of pH,an enzyme will lose its biologically active conformation.What term describes the state of the enzyme under these conditions?

Accepted Answer

A) denatured 
B) acidic 
C) basic 
D) buffered 
E) noncovalent 
A) denatured 
B) acidic 
C) basic 
D) buffered 
E) noncovalent

Question 16

The presence of an enzyme will alter the relative ratio of product to reactant for a biochemical reaction.

Accepted Answer

A) True 
 B)False

Question 17

Which of the following describes the function of the enzyme cis-trans isomerase?

Accepted Answer

A) It breaks the double bond in an unsaturated fatty acid. 
B) It converts pentose sugars to hexose sugars. 
C) It converts between isomers on a disubstituted benzene ring. 
D) It converts between the boat and chair conformations of a cyclohexane. 
E) It breaks and re-forms a double bond to change the arrangement of the groups around a double bond. 
A) It breaks the double bond in an unsaturated fatty acid. 
B) It converts pentose sugars to hexose sugars. 
C) It converts between isomers on a disubstituted benzene ring. 
D) It converts between the boat and chair conformations of a cyclohexane. 
E) It breaks and re-forms a double bond to change the arrangement of the groups around a double bond.

Question 18

Many enzymes are destroyed if the temperature rises significantly above 37ºC.

Accepted Answer

A) True 
 B)False

Question 19

Proteases,or proteolytic enzymes,are responsible for which of the following functions?

Accepted Answer

A) formation of the zwitterion form of a protein 
B) hydrolysis of the ester bonds in dietary triglycerides 
C) hydrolysis of the peptide bonds between amino acids in proteins 
D) formation of the glycosidic linkages in disaccharides and polysaccharides 
E) formation of bacterial cell walls 
A) formation of the zwitterion form of a protein 
B) hydrolysis of the ester bonds in dietary triglycerides 
C) hydrolysis of the peptide bonds between amino acids in proteins 
D) formation of the glycosidic linkages in disaccharides and polysaccharides 
E) formation of bacterial cell walls

Question 20

The enzyme fumarase is a lyase enzyme that catalyzes the hydration of fumarate to give malate.What is the structure of malate?

Accepted Answer

A) 
  
B) 
  
C) 
  
D) 
  
E) 
  
A) 
  
B) 
  
C) 
  
D) 
  
E)

Exam 19: Enzymes

Binding of a negative effector converts an active site on an enzyme into the active configuration.

Lactase is an enzyme that catalyzes the following reaction.Which statement describing this reaction is FALSE?

The rates of enzyme-catalyzed reactions increase with increasing pH.

Which of the following describes how an enzyme can affect the transition state in an enzyme-catalyzed reaction?

The penicillin class of antibiotics is inhibitors of an enzyme responsible for the formation of bacterial cell walls.The penicillin covalently binds to a serine residue in the active site of the enzyme,as depicted below.What type of bond is formed between the penicillin and the active site?

Carboxypetidase A is a highly folded,globular protein that functions as a protease enzyme.Which of the following is a likely assumption about the amino acid residues that exist on the exterior of this folded protein?

What is the function of a lyase enzyme?

Which of the following will NOT destroy an enzyme by denaturation?

The arrival of a nerve impulse at the end plate of the nerve axon results in an influx of what ion?

Which of the following is NOT a class of enzymes?

The rate of an enzyme-catalyzed reaction initially increases with an increase in the substrate concentration,but eventually reaches a maximum value,even though the concentration of substrate continues to increase.Which of the following best explains why?

Sucrase is an example of an enzyme that displays absolute specificity.What does the term "absolute specificity" indicate about an enzyme?

What type of enzyme regulation occurs when the final product of a pathway shuts off the entire pathway for its own synthesis?

The enzyme acetylcholinesterase catalyzes the hydrolysis of acetylcholine.Which of the following is a product of this hydrolysis reaction?

At extremes of pH,an enzyme will lose its biologically active conformation.What term describes the state of the enzyme under these conditions?

The presence of an enzyme will alter the relative ratio of product to reactant for a biochemical reaction.

Which of the following describes the function of the enzyme cis-trans isomerase?

Many enzymes are destroyed if the temperature rises significantly above 37ºC.

Proteases,or proteolytic enzymes,are responsible for which of the following functions?

The enzyme fumarase is a lyase enzyme that catalyzes the hydration of fumarate to give malate.What is the structure of malate?

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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