Question 1

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 2

It is difficult to determine either Km or Vmax from a graph of velocity vs. substrate concentration because

Accepted Answer

A)  too much substrate is required to determine them. 
B)  the graph is sigmoidal. 
C)  an asymptotic value must be determined from the graph. 
D)  the points on the graph are often not spread out on the hyperbola. 
A)  too much substrate is required to determine them. 
B)  the graph is sigmoidal. 
C)  an asymptotic value must be determined from the graph. 
D)  the points on the graph are often not spread out on the hyperbola.

Question 3

Phosphorylation that changes an enzymeʹs 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 4

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 5

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 6

Most of the known enzymes are .

Accepted Answer

A)  oxidoreductases 
B)  transferases 
C)  hydrolases 
D)  lyases 
E)  isomerases 
A)  oxidoreductases 
B)  transferases 
C)  hydrolases 
D)  lyases 
E)  isomerases

Question 7

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 8

Affinity labels are radioactive competitive inhibitors used to identify the most important residues in an enzymeʹs active site.

Accepted Answer

A) True 
 B)False

Question 9

Select the correct class of enzyme for each of these reactions. A) isomerase
B) ligase
C) lyase
D) transferase
E) oxidoreductase
F) hydrolase
-L-aspartic acid +
a-ketoglutarate → oxaloacetic acid + L-Glutamate

Accepted Answer

The answer of Select the correct class of enzyme for...

Question 10

The concentrations of enzymes are determined by using pseudo first-order conditions in which

Accepted Answer

A)  S concentration is kept the same and the rate is measured. 
B)  E concentration is kept the same and the rate is measured. 
C)  S concentration is constant, E concentration varied and the rate is measured. 
D)  E concentration is constant, S concentration varied and the rate is measured. 
E)  All of the above 
A)  S concentration is kept the same and the rate is measured. 
B)  E concentration is kept the same and the rate is measured. 
C)  S concentration is constant, E concentration varied and the rate is measured. 
D)  E concentration is constant, S concentration varied and the rate is measured. 
E)  All of the above

Question 11

What type of inhibition is indicated by the data graphed below?

Accepted Answer

A)  competitive 
B)  uncompetitive 
C)  noncompetitive 
D)  irreversible 
A)  competitive 
B)  uncompetitive 
C)  noncompetitive 
D)  irreversible

Question 12

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 13

An inhibitor binds to a site other than the active site of the enzyme. Which statement below correlates with this observation?

Accepted Answer

A)  It must be a competitive inhibitor. 
B)  The inhibition must be irreversible. 
C)  It could be noncompetitive or uncompetitive inhibition. 
D)  It could be irreversible, competitive, noncompetitive or uncompetitive. The data do not relate to the type of inhibition. 
A)  It must be a competitive inhibitor. 
B)  The inhibition must be irreversible. 
C)  It could be noncompetitive or uncompetitive inhibition. 
D)  It could be irreversible, competitive, noncompetitive or uncompetitive. The data do not relate to the type of inhibition.

Question 14

Which of the following statements is FALSE?

Accepted Answer

A)  Enzymes make reactions 103 to 1020 times faster. 
B)  Enzymes lower the amount of energy needed for a reaction. 
C)  Enzymes are chemically unchanged during the actual catalytic process. 
D)  Enzymes speed up the attainment of a reaction equilibrium. 
E)  Enzymes are proteins. 
A)  Enzymes make reactions 103 to 1020 times faster. 
B)  Enzymes lower the amount of energy needed for a reaction. 
C)  Enzymes are chemically unchanged during the actual catalytic process. 
D)  Enzymes speed up the attainment of a reaction equilibrium. 
E)  Enzymes are proteins.

Question 15

The most common enzyme inhibitors are competitive inhibitors.

Accepted Answer

A) True 
 B)False

Question 16

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 17

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 18

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 19

The hydrophobic cleft in globular proteins which bind substrate molecules is called the .

Accepted Answer

A)  substrate pocket 
B)  modulator site 
C)  active site 
D)  activity site 
E)  oligomeric site 
A)  substrate pocket 
B)  modulator site 
C)  active site 
D)  activity site 
E)  oligomeric site

Question 20

When varying the substrate concentration at a fixed concentration of enzyme it is observed that at low concentrations of substrate the reaction is ,while at high concentrations of substrate the reaction is .

Accepted Answer

A)  maximal; initial 
B)  initial; maximal 
C)  second order; first order 
D)  first order; second order 
E)  first order; zero order 
A)  maximal; initial 
B)  initial; maximal 
C)  second order; first order 
D)  first order; second order 
E)  first order; zero order

Exam 5: Properties of Enzymes

Unlike typical catalyzed reactions in organic chemistry enzyme reactions are

It is difficult to determine either Km or Vmax from a graph of velocity vs. substrate concentration because

Phosphorylation that changes an enzymeʹs activity is an example of .

Oxidases, peroxidases, oxygenases or reductases are all

Which equilibrium below applies to noncompetitive inhibition?

Most of the known enzymes are .

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?

Affinity labels are radioactive competitive inhibitors used to identify the most important residues in an enzymeʹs active site.

Select the correct class of enzyme for each of these reactions. A) isomerase B) ligase C) lyase D) transferase E) oxidoreductase F) hydrolase -L-aspartic acid + a-ketoglutarate → oxaloacetic acid + L-Glutamate

The concentrations of enzymes are determined by using pseudo first-order conditions in which

What type of inhibition is indicated by the data graphed below?

Which enzyme below is fastest?

An inhibitor binds to a site other than the active site of the enzyme. Which statement below correlates with this observation?

Which of the following statements is FALSE?

The most common enzyme inhibitors are competitive inhibitors.

Which statement is false about covalent modification?

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.

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

The hydrophobic cleft in globular proteins which bind substrate molecules is called the .

When varying the substrate concentration at a fixed concentration of enzyme it is observed that at low concentrations of substrate the reaction is ,while at high concentrations of substrate the reaction is .

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 Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

Dna Replication, Repair, and Recombination

Transcription and Rna Processing

Protein Synthesis

Recombinant Dna Technology

Filters

It is difficult to determine either K_mor V_maxfrom a graph of velocity vs. substrate concentration because