Question 1

Select the correct class of enzyme for each of these reactions.
-L-aspartic acid + a-ketoglutarate → oxaloacetic acid + L-Glutamate

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 D

Question 2

When there are two substrates in a reaction,the reaction is said to be second order if ________.

Accepted Answer

A) the reaction is first order with respect to each substrate concentration 
B) the maximum rate is independent of either substrate's concentration 
C) the substrate concentrations are equal 
D) it proceeds at twice the rate upon double the concentrations of both substrates 
A) the reaction is first order with respect to each substrate concentration 
B) the maximum rate is independent of either substrate's concentration 
C) the substrate concentrations are equal 
D) it proceeds at twice the rate upon double the concentrations of both substrates A

Question 3

In ________ inhibition the inhibitor binds at a site other than the active site,but alters the active site to prevent binding of the normal substrate.

Accepted Answer

A) classical competitive 
B) non-classical competitive 
C) noncompetitive 
D) uncompetitive 
E) irreversible 
A) classical competitive 
B) non-classical competitive 
C) noncompetitive 
D) uncompetitive 
E) irreversible B

Question 4

The reason to rewrite the Michaelis-Menten equation (such as the Lineweaver-Burk plot)is to

Accepted Answer

A) visualize reactions better. 
B) form enzyme kinetic data as a hyperbolic curve. 
C) calculate catalytic proficiency. 
D) calculate Vmax and Km. 
A) visualize reactions better. 
B) form enzyme kinetic data as a hyperbolic curve. 
C) calculate catalytic proficiency. 
D) calculate Vmax and Km.

Question 5

The ratio of kcat/Km for each of two different substrates present in equal concentrations in an enzyme reaction will measure enzyme affinity because

Accepted Answer

A) the rates of P formation are given by the values found for each substrate. 
B) the rates of P formation are the same for each substrate. 
C) it is an indication of the formation of ES for each substrate. 
D) All of the above. 
A) the rates of P formation are given by the values found for each substrate. 
B) the rates of P formation are the same for each substrate. 
C) it is an indication of the formation of ES for each substrate. 
D) All of the above.

Question 6

The quaternary structure of hemoglobin changes from the T state to the R state ________.

Accepted Answer

A) only after four molecules of O² are bound 
B) after the binding of one molecule of O² causes a change in the primary structure 
C) when hemoglobin is completely deoxygenated 
D) when at least one subunit on each dimeric unit (αβ dimer)is oxygenated 
A) only after four molecules of O² are bound 
B) after the binding of one molecule of O² causes a change in the primary structure 
C) when hemoglobin is completely deoxygenated 
D) when at least one subunit on each dimeric unit (αβ dimer)is oxygenated

Question 7

The enymatic rate constant (kcat/Km)of orotidine 5'-phosphate decarboxylase is 6 × 10⁷ M-1s-¹ and the nonenzymatic rate constant (kn)is 3 × 10-¹⁶ s-¹.What is the value of the enzyme's catalytic proficiency?

Accepted Answer

A)  2 x 1023 M-1 
B)  5 x 10-24 M 
C)  12 x 10-9 M-1s-2 
D)  8.3 x 107 Ms2  
E)  Cannot calcuate the profeciency without knowing the value Vmax. 
A)  2 x 1023 M-1 
B)  5 x 10-24 M 
C)  12 x 10-9 M-1s-2 
D)  8.3 x 107 Ms2  
E)  Cannot calcuate the profeciency without knowing the value Vmax.

Question 8

An enzyme is irreversibly inhibited by diisopropylfluorophosphate (DFP).What does this show?

Accepted Answer

A) The enzyme has been denatured by DFP. 
B) Serine is likely an important residue in the active site. 
C) DFP is an allosteric modulator of the enzyme. 
D) DFP is an analog of the enzyme's substrate. 
A) The enzyme has been denatured by DFP. 
B) Serine is likely an important residue in the active site. 
C) DFP is an allosteric modulator of the enzyme. 
D) DFP is an analog of the enzyme's substrate.

Question 9

In a ping-pong reaction which does not occur?

Accepted Answer

A) One product is released before a second substrate is bound. 
B) The enzyme covalently binds a portion of the first substrate. 
C) The enzyme is permanently converted to an altered form by the first substrate. 
D) A group is transferred from one substrate to another. 
A) One product is released before a second substrate is bound. 
B) The enzyme covalently binds a portion of the first substrate. 
C) The enzyme is permanently converted to an altered form by the first substrate. 
D) A group is transferred from one substrate to another.

Question 10

Select the correct class of enzyme for each of these reactions.
-Lactate + NAD+ → Pyruvate + NADH + H+

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 11

Phosphorylation that changes an enzyme's activity is an example of ________.

Accepted Answer

A) covalent modification 
B) allosteric regulation 
C) sequential modification 
D) site-directed mutagenesis 
A) covalent modification 
B) allosteric regulation 
C) sequential modification 
D) site-directed mutagenesis

Question 12

The catalytic proficiency of an enzyme is the ________.

Accepted Answer

A) turnover number 
B) Km/[E] 
C) rate constant with the enzyme divided by the rate constant without the enzyme 
D) rate constant with the enzyme times the rate constant without the enzyme 
A) turnover number 
B) Km/[E] 
C) rate constant with the enzyme divided by the rate constant without the enzyme 
D) rate constant with the enzyme times the rate constant without the enzyme

Question 13

The following data were obtained in the presence and absence of inhibitor.What type of inhibition is shown?

Accepted Answer

A) Competitive. 
B) Uncompetitive. 
C) Noncompetitive. 
D) Irreversible. 
E) Cannot tell inhibition type from the information given. 
A) Competitive. 
B) Uncompetitive. 
C) Noncompetitive. 
D) Irreversible. 
E) Cannot tell inhibition type from the information given.

Question 14

The initial velocity of an enzyme reaction (v0)describes

Accepted Answer

A) the concentration of the enzyme at maximal velocity. 
B) the concentration of substrate at maximal velocity. 
C) the concentration of both at the start of the reaction. 
D) the rate of the reaction when the substrate and enzyme are first mixed. 
A) the concentration of the enzyme at maximal velocity. 
B) the concentration of substrate at maximal velocity. 
C) the concentration of both at the start of the reaction. 
D) the rate of the reaction when the substrate and enzyme are first mixed.

Question 15

Allosteric modulators seldom resemble the substrate or product of the enzyme.What does this observation show?

Accepted Answer

A) Modulators likely bind at a site other than the active site. 
B) Modulators always act as activators. 
C) Modulators bind non-covalently to the enzyme. 
D) The enzyme catalyzes more than one reaction. 
A) Modulators likely bind at a site other than the active site. 
B) Modulators always act as activators. 
C) Modulators bind non-covalently to the enzyme. 
D) The enzyme catalyzes more than one reaction.

Question 16

Select the correct class of enzyme for each of these reactions.
-Glucose-6-phosphate → Fructose-6-phosphate

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

What is the shape of a typical plot of initial rate vs.substrate concentration for an enzyme catalyzed reaction that follows Michaelis-Menton kinetics?

Accepted Answer

A) Sigmoidal. 
B) Parabolic. 
C) Sinusoidal. 
D) Bell curve. 
E) Hyperbolic. 
A) Sigmoidal. 
B) Parabolic. 
C) Sinusoidal. 
D) Bell curve. 
E) Hyperbolic.

Question 18

In an enzyme reaction involving one enzyme and one substrate,the rate of the reaction depends on

Accepted Answer

A) substrate concentration. 
B) enzyme concentration. 
C) both substrate and enzyme concentrations. 
D) the enzyme concentration at first and the substrate concentration later on. 
A) substrate concentration. 
B) enzyme concentration. 
C) both substrate and enzyme concentrations. 
D) the enzyme concentration at first and the substrate concentration later on.

Question 19

In a first order enzyme-catalyzed reaction,the velocity of the reaction is proportional to the ________,while in a zero order enzyme-catalyzed reaction,the velocity of the reaction is proportional to the ________.

Accepted Answer

A) amount of enzyme;concentration of substrate 
B) concentration of substrate;amount of enzyme 
C) concentration of substrate;speed of the reaction 
D) speed of the reaction;concentration of substrate 
A) amount of enzyme;concentration of substrate 
B) concentration of substrate;amount of enzyme 
C) concentration of substrate;speed of the reaction 
D) speed of the reaction;concentration of substrate

Question 20

How is the catalytic proficiency defined?

Accepted Answer

A) It is the reciprocal of the turnover number. 
B) It is the logarithm of the Michaelis-Menton constant. 
C) It is equal to the rate constants for a reaction in the presence of the enzyme divided by the rate constant for the same reaction in the absence of the enzyme. 
D) It is the rate of the enzyme-catalyzed reaction in the presences of a standard concentration of enzyme. 
A) It is the reciprocal of the turnover number. 
B) It is the logarithm of the Michaelis-Menton constant. 
C) It is equal to the rate constants for a reaction in the presence of the enzyme divided by the rate constant for the same reaction in the absence of the enzyme. 
D) It is the rate of the enzyme-catalyzed reaction in the presences of a standard concentration of enzyme.

Exam 5: Properties of Enzymes

Select the correct class of enzyme for each of these reactions. -L-aspartic acid + a-ketoglutarate → oxaloacetic acid + L-Glutamate

When there are two substrates in a reaction,the reaction is said to be second order if ________.

In ________ inhibition the inhibitor binds at a site other than the active site,but alters the active site to prevent binding of the normal substrate.

The reason to rewrite the Michaelis-Menten equation (such as the Lineweaver-Burk plot)is to

The ratio of kcat/Km for each of two different substrates present in equal concentrations in an enzyme reaction will measure enzyme affinity because

The quaternary structure of hemoglobin changes from the T state to the R state ________.

The enymatic rate constant (kcat/Km)of orotidine 5'-phosphate decarboxylase is 6 × 10⁷ M-1s-¹ and the nonenzymatic rate constant (kn)is 3 × 10-¹⁶ s-¹.What is the value of the enzyme's catalytic proficiency?

An enzyme is irreversibly inhibited by diisopropylfluorophosphate (DFP).What does this show?

In a ping-pong reaction which does not occur?

Select the correct class of enzyme for each of these reactions. -Lactate + NAD+ → Pyruvate + NADH + H+

Phosphorylation that changes an enzyme's activity is an example of ________.

The catalytic proficiency of an enzyme is the ________.

The following data were obtained in the presence and absence of inhibitor.What type of inhibition is shown?

The initial velocity of an enzyme reaction (v0)describes

Allosteric modulators seldom resemble the substrate or product of the enzyme.What does this observation show?

Select the correct class of enzyme for each of these reactions. -Glucose-6-phosphate → Fructose-6-phosphate

What is the shape of a typical plot of initial rate vs.substrate concentration for an enzyme catalyzed reaction that follows Michaelis-Menton kinetics?

In an enzyme reaction involving one enzyme and one substrate,the rate of the reaction depends on

In a first order enzyme-catalyzed reaction,the velocity of the reaction is proportional to the ________,while in a zero order enzyme-catalyzed reaction,the velocity of the reaction is proportional to the ________.

How is the catalytic proficiency defined?

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

Filters

In a first order enzyme-catalyzed reaction,the velocity of the reaction is proportional to the ,while in a zero order enzyme-catalyzed reaction,the velocity of the reaction is proportional to the .