Question 1

Which groups of amino acids are likely to be found in the active site of an enzyme?

Accepted Answer

A)  leucine, lysine, alanine. 
B)  cysteine, isoleucine, phenylalanine. 
C)  tyrosine, threonine, leucine. 
D)  serine, histidine, aspartate. 
A)  leucine, lysine, alanine. 
B)  cysteine, isoleucine, phenylalanine. 
C)  tyrosine, threonine, leucine. 
D)  serine, histidine, aspartate.

Question 2

Allosteric effectors

Accepted Answer

A)  typically bind to the enzyme's active site. 
B)  typically bind at a site unique from the active site. 
C)  bind to the substrate rather than the enzyme. 
D)  only bind to the enzyme-substrate complex. 
A)  typically bind to the enzyme's active site. 
B)  typically bind at a site unique from the active site. 
C)  bind to the substrate rather than the enzyme. 
D)  only bind to the enzyme-substrate complex.

Question 3

Is the Michaelis-Menten equation useful when studying allosteric enzymes?

Accepted Answer

A)  Yes 
B)  No 
C)  Only if the enzyme displays positive cooperativity. 
D)  Only if the enzyme displays negative cooperativity. 
A)  Yes 
B)  No 
C)  Only if the enzyme displays positive cooperativity. 
D)  Only if the enzyme displays negative cooperativity.

Question 4

Exhibit 7A   Refer to Exhibit 7A.Which two enzymes would be the most likely ones to regulate if this pathway is dedicated to the formation of only one product?

Accepted Answer

A)  1 and 2 
B)  1 and 3 
C)  1 and 5 
D)  2 and 4 
E)  4 and 5 
A)  1 and 2 
B)  1 and 3 
C)  1 and 5 
D)  2 and 4 
E)  4 and 5

Question 5

Which of the following is true?

Accepted Answer

A)  Phosphorylation always increases enzyme activity 
B)  Kinases often use AMP as a co-substrate in their phosphorylation reactions 
C)  Some enzymes are activated by phosphorylation while others are inhibited 
D)  ADP is the most common substrate for a kinase reaction 
A)  Phosphorylation always increases enzyme activity 
B)  Kinases often use AMP as a co-substrate in their phosphorylation reactions 
C)  Some enzymes are activated by phosphorylation while others are inhibited 
D)  ADP is the most common substrate for a kinase reaction

Question 6

Kinase reactions describe enzymes which

Accepted Answer

A)  add phosphate groups to another molecule. 
B)  oxidize alcohols to aldehydes. 
C)  use NAD+/NADH in their reactions. 
D)  transfer groups from one part of a molecule to another. 
E)  add or remove double bonds in molecules. 
A)  add phosphate groups to another molecule. 
B)  oxidize alcohols to aldehydes. 
C)  use NAD+/NADH in their reactions. 
D)  transfer groups from one part of a molecule to another. 
E)  add or remove double bonds in molecules.

Question 7

Which of the following statements about coenzymes is true?

Accepted Answer

A)  They are commonly derived from vitamins. 
B)  They bind to the active site region on specific types of enzymes. 
C)  They can be metal ions, such as Zn(II). 
D)  NAD+, FAD and biotin are all examples of coenzymes. 
E)  All of these statements are true. 
A)  They are commonly derived from vitamins. 
B)  They bind to the active site region on specific types of enzymes. 
C)  They can be metal ions, such as Zn(II). 
D)  NAD+, FAD and biotin are all examples of coenzymes. 
E)  All of these statements are true.

Question 8

Exhibit 7A   Refer to Exhibit 7A.The final product,R,will most likely inhibit which reaction?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5 
A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 9

The main distinguishing feature of the concerted model for the behavior of allosteric enzymes is that

Accepted Answer

A)  the conformation of all subunits changes simultaneously. 
B)  it applies only to dimeric enzymes. 
C)  it involves three possible conformations for all subunits. 
D)  the T and R conformations exist in roughly equal amounts. 
A)  the conformation of all subunits changes simultaneously. 
B)  it applies only to dimeric enzymes. 
C)  it involves three possible conformations for all subunits. 
D)  the T and R conformations exist in roughly equal amounts.

Question 10

Many metabolic pathways involve multistep reactions.Consider the following pathway.   Which of the following would be an example of feedback inhibition?

Accepted Answer

A)  the product of the final reaction, F, interacting with E1. 
B)  F interacting with an allosteric site in E4. 
C)  B interacting with an allosteric site in E1. 
D)  all of the intermediates or products in the reaction interacting with the active site in E1. 
A)  the product of the final reaction, F, interacting with E1. 
B)  F interacting with an allosteric site in E4. 
C)  B interacting with an allosteric site in E1. 
D)  all of the intermediates or products in the reaction interacting with the active site in E1.

Question 11

Zymogens are

Accepted Answer

A)  inactive precursors of enzymes which can be activated by the irreversible cleavage of covalent bonds. 
B)  inactive forms of enzymes which require phosphorylation by a kinase to become active. 
C)  allosteric enzymes that are always in the R state. 
D)  allosteric enzymes that are always in the T state. 
A)  inactive precursors of enzymes which can be activated by the irreversible cleavage of covalent bonds. 
B)  inactive forms of enzymes which require phosphorylation by a kinase to become active. 
C)  allosteric enzymes that are always in the R state. 
D)  allosteric enzymes that are always in the T state.

Question 12

Which of the following best describes negative cooperativity?

Accepted Answer

A)  Binding of one substrate molecule prevents the enzyme from working at all. 
B)  Binding of one substrate molecule inhibits the binding of a second substrate. 
C)  Binding of one substrate molecule enhances the binding of a second substrate. 
D)  Binding of one substrate molecule inhibits the binding of other effectors. 
A)  Binding of one substrate molecule prevents the enzyme from working at all. 
B)  Binding of one substrate molecule inhibits the binding of a second substrate. 
C)  Binding of one substrate molecule enhances the binding of a second substrate. 
D)  Binding of one substrate molecule inhibits the binding of other effectors.

Question 13

A transition-state analog is likely to bind to an enzyme

Accepted Answer

A)  more tightly than the substrate. 
B)  less tightly than the substrate. 
C)  about as tightly as the substrate. 
D)  at a site other than the catalytic site. 
A)  more tightly than the substrate. 
B)  less tightly than the substrate. 
C)  about as tightly as the substrate. 
D)  at a site other than the catalytic site.

Question 14

Cofactors are

Accepted Answer

A)  non-protein in chemical nature. 
B)  always small proteins. 
C)  modified amino acids. 
D)  never required for enzymatic activity. 
A)  non-protein in chemical nature. 
B)  always small proteins. 
C)  modified amino acids. 
D)  never required for enzymatic activity.

Question 15

The serine in the active site of chymotrypsin functions as

Accepted Answer

A)  a Lewis acid. 
B)  a metal ion. 
C)  an electrophile. 
D)  a nucleophile. 
A)  a Lewis acid. 
B)  a metal ion. 
C)  an electrophile. 
D)  a nucleophile.

Question 16

Which of the following is true?

Accepted Answer

A)  Allosteric enzymes are rarely important in the regulation of metabolic pathways. 
B)  Michaelis-Menten kinetics describe the reactions of allosteric enzymes 
C)  Allosteric enzymes have a hyperbolic plot of reaction rate vs. substrate concentration 
D)  none of these is true 
A)  Allosteric enzymes are rarely important in the regulation of metabolic pathways. 
B)  Michaelis-Menten kinetics describe the reactions of allosteric enzymes 
C)  Allosteric enzymes have a hyperbolic plot of reaction rate vs. substrate concentration 
D)  none of these is true

Question 17

Allosteric enzymes must exhibit which of the following?

Accepted Answer

A)  feedback inhibition 
B)  a phosphorylation site 
C)  general acid-base catalysis 
D)  a quaternary structure 
A)  feedback inhibition 
B)  a phosphorylation site 
C)  general acid-base catalysis 
D)  a quaternary structure

Question 18

Phosphorylation of enzymes

Accepted Answer

A)  has no effect on their catalytic activity. 
B)  does not require ATP. 
C)  usually takes place on serine, threonine, and tyrosine residues. 
D)  is not easily characterized. 
A)  has no effect on their catalytic activity. 
B)  does not require ATP. 
C)  usually takes place on serine, threonine, and tyrosine residues. 
D)  is not easily characterized.

Question 19

The initial bond formation in the covalent intermediate in the reaction catalyzed by chymotrypsin is between

Accepted Answer

A)  serine and the carbonyl carbon in the peptide backbone 
B)  serine and the nitrogen in the peptide backbone 
C)  histidine and the carbonyl carbon in the peptide backbone 
D)  histidine and the nitrogen in the peptide backbone 
A)  serine and the carbonyl carbon in the peptide backbone 
B)  serine and the nitrogen in the peptide backbone 
C)  histidine and the carbonyl carbon in the peptide backbone 
D)  histidine and the nitrogen in the peptide backbone

Question 20

Which of the following enzymes is not a serine protease?

Accepted Answer

A)  trypsin 
B)  chymotrypsin 
C)  thrombin 
D)  aspartyl transcarbamylase (ATCase) 
A)  trypsin 
B)  chymotrypsin 
C)  thrombin 
D)  aspartyl transcarbamylase (ATCase)

Exam 7: The Behavior of Proteins: Enzymes, Mechanisms, and Control

Which groups of amino acids are likely to be found in the active site of an enzyme?

Allosteric effectors

Is the Michaelis-Menten equation useful when studying allosteric enzymes?

Exhibit 7A Refer to Exhibit 7A.Which two enzymes would be the most likely ones to regulate if this pathway is dedicated to the formation of only one product?

Which of the following is true?

Kinase reactions describe enzymes which

Which of the following statements about coenzymes is true?

Exhibit 7A Refer to Exhibit 7A.The final product,R,will most likely inhibit which reaction?

The main distinguishing feature of the concerted model for the behavior of allosteric enzymes is that

Many metabolic pathways involve multistep reactions.Consider the following pathway. Which of the following would be an example of feedback inhibition?

Zymogens are

Which of the following best describes negative cooperativity?

A transition-state analog is likely to bind to an enzyme

Cofactors are

The serine in the active site of chymotrypsin functions as

Which of the following is true?

Allosteric enzymes must exhibit which of the following?

Phosphorylation of enzymes

The initial bond formation in the covalent intermediate in the reaction catalyzed by chymotrypsin is between

Which of the following enzymes is not a serine protease?

Biochemistry and the Organization of Cells

Water: The Solvent for Biochemical Reactions

Amino Acids and Peptides

The Three-Dimensional Structure of Proteins

Protein Purification and Characterization Techniques

The Behavior of Proteins: Enzymes

Lipids and Proteins Are Associated in Biological Membranes

Nucleic Acids: How Structure Conveys Information

Biosynthesis of Nucleic Acids: Replication

Transcription of the Genetic Code: Biosynthesis of Rna

Protein Synthesis: Translation of the Genetic Message

Nucleic Acid Biotechnology Techniques

Viruses, Cancer, and Immunology

The Importance of Energy Changes and Electron Transfer in Metabolism

Carbohydrates

Glycolysis

Storage Mechanisms and Control in Carbohydrate Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Lipid Metabolism

Photosynthesis

The Metabolism of Nitrogen

Integration of Metabolism: Cellular Signaling

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