Question 1

When two different substrates react to form two different products,the rate constants for each separate substrate can be determined by

Accepted Answer

A) varying one substrate at a time,keeping the other in excess. 
B) varying both substrates and measuring the appearance of the two products. 
C) limiting one substrate and varying the other. 
D) keeping both substrate concentrations high and detecting one product at a time. 
A) varying one substrate at a time,keeping the other in excess. 
B) varying both substrates and measuring the appearance of the two products. 
C) limiting one substrate and varying the other. 
D) keeping both substrate concentrations high and detecting one product at a time.

Question 2

Which statement is false about covalent modification?

Accepted Answer

A) It is reversible. 
B) It is slightly slower than allosteric regulation. 
C) It usually uses the same enzyme for activation and inactivation. 
D) All of the above. 
A) It is reversible. 
B) It is slightly slower than allosteric regulation. 
C) It usually uses the same enzyme for activation and inactivation. 
D) All of the above.

Question 3

Which equilibrium below applies to noncompetitive inhibition?

Accepted Answer

A) I 
B) II 
C) III 
D) IV 
A) I 
B) II 
C) III 
D) IV

Question 4

Enzymes that join two substrates and require energy of a nucleoside triphosphate (such as ATP)to do so are called

Accepted Answer

A) isomerases. 
B) lyases. 
C) ligases. 
D) synthetases. 
E) Both c and d. 
A) isomerases. 
B) lyases. 
C) ligases. 
D) synthetases. 
E) Both c and d.

Question 5

Rational drug design involves the study of enzyme structure and the use of computers to generate structures of possible enzyme inhibitors.

Accepted Answer

A) True 
 B)False

Question 6

Nonclassical competitive inhibition involves ________.

Accepted Answer

A) binding of the substrate at both the active site and at the inhibitor site 
B) binding of either the substrate to the active site or the inhibitor to its own binding site thus preventing the other from binding 
C) binding of the inhibitor to the substrate followed by binding of this complex to the active site 
D) chemical removal of the substrate from the active site by reaction with the inhibitor 
A) binding of the substrate at both the active site and at the inhibitor site 
B) binding of either the substrate to the active site or the inhibitor to its own binding site thus preventing the other from binding 
C) binding of the inhibitor to the substrate followed by binding of this complex to the active site 
D) chemical removal of the substrate from the active site by reaction with the inhibitor

Question 7

Unlike typical catalyzed reactions in organic chemistry enzyme reactions are

Accepted Answer

A) usually stereospecific. 
B) reaction specific. 
C) essentially 100% efficient. 
D) modulated to change activity levels. 
E) All of the above. 
A) usually stereospecific. 
B) reaction specific. 
C) essentially 100% efficient. 
D) modulated to change activity levels. 
E) All of the above.

Question 8

Which enzyme below is fastest?

Accepted Answer

A) Kinase,kcat = 103. 
B) Papain,kcat = 10. 
C) Carboxypeptidase,kcat = 102. 
D) Catalase,kcat = 107. 
A) Kinase,kcat = 103. 
B) Papain,kcat = 10. 
C) Carboxypeptidase,kcat = 102. 
D) Catalase,kcat = 107.

Question 9

Which statement is false about allosteric regulation?

Accepted Answer

A) It is usually the mode of regulation for the last step in reaction pathways since this step produces the final product. 
B) Cellular response is faster with allosteric control than by controlling enzyme concentration in the cell. 
C) The regulation usually is important to the conservation of energy and materials in cells. 
D) Allosteric modulators bind non-covalently at sites other than the active site and induce conformational changes in the enzyme. 
A) It is usually the mode of regulation for the last step in reaction pathways since this step produces the final product. 
B) Cellular response is faster with allosteric control than by controlling enzyme concentration in the cell. 
C) The regulation usually is important to the conservation of energy and materials in cells. 
D) Allosteric modulators bind non-covalently at sites other than the active site and induce conformational changes in the enzyme.

Question 10

The difference between uncompetitive and noncompetitive inhibitors is that

Accepted Answer

A) uncompetitive inhibitors bind irreversibly. 
B) 1 / V max is the same for all concentrations of uncompetitive inhibitors. 
C) an uncompetitive inhibitor binds only to ES. 
D) a competitive inhibitor binds only to E. 
A) uncompetitive inhibitors bind irreversibly. 
B) 1 / V max is the same for all concentrations of uncompetitive inhibitors. 
C) an uncompetitive inhibitor binds only to ES. 
D) a competitive inhibitor binds only to E.

Question 11

Which might be most useful for determining the amino acid residues in an enzyme's active site?

Accepted Answer

A) Use an irreversible inhibitor that reacts with the side chains of specific amino acids. 
B) Determine the entire primary structure of the protein. 
C) Use a competitive inhibitor and plot the rate vs concentration of inhibitor. 
D) Unfold the enzyme with urea and 2-mercaptoethanol.Then incubate and crystallize it in the presence of the substrate followed by X-ray crystallography. 
A) Use an irreversible inhibitor that reacts with the side chains of specific amino acids. 
B) Determine the entire primary structure of the protein. 
C) Use a competitive inhibitor and plot the rate vs concentration of inhibitor. 
D) Unfold the enzyme with urea and 2-mercaptoethanol.Then incubate and crystallize it in the presence of the substrate followed by X-ray crystallography.

Question 12

At sufficiently high substrate concentration all types of reversible inhibition can be overwhelmed.At high substrate concentration the enzyme will be saturated and the reaction will proceed at the same maximum velocity as in the absence of inhibitor.

Accepted Answer

A) True 
 B)False

Question 13

Which is not an explanation of why site-directed mutagenesis is a more powerful tool than many other techniques for determining important residues in an enzyme?

Accepted Answer

A) It is a more specific technique than irreversible inhibition experiments. 
B) It can be used on enzymes for which no specific irreversible inhibitor is known. 
C) It allows for testing of the specific function of amino acid side chains in an enzyme. 
D) It is especially useful for enzymes whose sequence is not known. 
A) It is a more specific technique than irreversible inhibition experiments. 
B) It can be used on enzymes for which no specific irreversible inhibitor is known. 
C) It allows for testing of the specific function of amino acid side chains in an enzyme. 
D) It is especially useful for enzymes whose sequence is not known.

Question 14

Oxidases,peroxidases,oxygenases or reductases are all

Accepted Answer

A) lyases. 
B) synthases. 
C) synthetases. 
D) oxidoreductases. 
E) hydrolases. 
A) lyases. 
B) synthases. 
C) synthetases. 
D) oxidoreductases. 
E) hydrolases.

Question 15

Reversible inhibitors can be separated from solutions of enzymes by dialysis.

Accepted Answer

A) True 
 B)False

Question 16

Select the correct class of enzyme for each of these reactions.
-Sucrose + H₂O → Fructose + Glucose

Accepted Answer

A) oxidoreductase 
B) lyase 
C) isomerase 
D) transferase 
E) hydrolase
F)ligase 
A) oxidoreductase 
B) lyase 
C) isomerase 
D) transferase 
E) hydrolase
F)ligase

Question 17

Which is not a reason for metabolite channeling?

Accepted Answer

A) Protection of intermediates from degradation. 
B) Increasing the overall rate of a reaction. 
C) Producing locally high concentrations of intermediates. 
D) Ensuring the enzyme is properly regulated. 
A) Protection of intermediates from degradation. 
B) Increasing the overall rate of a reaction. 
C) Producing locally high concentrations of intermediates. 
D) Ensuring the enzyme is properly regulated.

Question 18

Which of the following statements is FALSE?

Accepted Answer

A) The word enzyme is from a Greek word meaning "in yeast." 
B) Enzymes are always made of protein. 
C) The first enzyme was crystallized in 1926. 
D) Enzymes can couple two different reactions. 
A) The word enzyme is from a Greek word meaning "in yeast." 
B) Enzymes are always made of protein. 
C) The first enzyme was crystallized in 1926. 
D) Enzymes can couple two different reactions.

Question 19

The Michaelis constant,Km,is equal to the ________.

Accepted Answer

A) maximum velocity that any given enzyme reaction can achieve 
B) substrate concentration which gives the best enzyme assay for an enzyme reaction 
C) substrate concentration when the rate is equal to half its maximal value 
D) maximum velocity divided by two 
A) maximum velocity that any given enzyme reaction can achieve 
B) substrate concentration which gives the best enzyme assay for an enzyme reaction 
C) substrate concentration when the rate is equal to half its maximal value 
D) maximum velocity divided by two

Question 20

Which step in an enzyme-catalyzed reaction was assumed to be negligible by Michaelis and Menton?

Accepted Answer

A) Formation of ES from E + P. 
B) Formation of E + P from ES. 
C) Conversion of ES to E + S. 
D) Formation of ES from E + S. 
A) Formation of ES from E + P. 
B) Formation of E + P from ES. 
C) Conversion of ES to E + S. 
D) Formation of ES from E + S.

Exam 5: Properties of Enzymes

When two different substrates react to form two different products,the rate constants for each separate substrate can be determined by

Which statement is false about covalent modification?

Which equilibrium below applies to noncompetitive inhibition?

Enzymes that join two substrates and require energy of a nucleoside triphosphate (such as ATP)to do so are called

Rational drug design involves the study of enzyme structure and the use of computers to generate structures of possible enzyme inhibitors.

Nonclassical competitive inhibition involves ________.

Unlike typical catalyzed reactions in organic chemistry enzyme reactions are

Which enzyme below is fastest?

Which statement is false about allosteric regulation?

The difference between uncompetitive and noncompetitive inhibitors is that

Which might be most useful for determining the amino acid residues in an enzyme's active site?

At sufficiently high substrate concentration all types of reversible inhibition can be overwhelmed.At high substrate concentration the enzyme will be saturated and the reaction will proceed at the same maximum velocity as in the absence of inhibitor.

Which is not an explanation of why site-directed mutagenesis is a more powerful tool than many other techniques for determining important residues in an enzyme?

Oxidases,peroxidases,oxygenases or reductases are all

Reversible inhibitors can be separated from solutions of enzymes by dialysis.

Select the correct class of enzyme for each of these reactions. -Sucrose + H₂O → Fructose + Glucose

Which is not a reason for metabolite channeling?

Which of the following statements is FALSE?

The Michaelis constant,Km,is equal to the ________.

Which step in an enzyme-catalyzed reaction was assumed to be negligible by Michaelis and Menton?

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

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