Question 1

Cells can develop a resistance to drugs by increasing the cellular concentration of the enzyme that that drug inhibits.If a cell increases its concentration of a given enzyme to 10 times the normal amount,which parameters listed below will be increased ten-fold?
Km
 KI
[S]
Vmax
v0 when [S] = Km
kcat
Catalytic efficiency

Accepted Answer

Only V_max and...

Question 2

Define the term "suicide inhibitor."

Accepted Answer

A suicide inhibitor is a molecule that i...

Question 3

To calculate the turnover number of an enzyme,you need to know:

Accepted Answer

A)  the enzyme concentration.
B)  the initial velocity of the catalyzed reaction at [S] >> Km.
C)  the initial velocity of the catalyzed reaction at low [S].
D)  the Km for the substrate.
E)  both A and B.F) A) and D)
G) All of the above

Question 4

Vmax for an enzyme-catalyzed reaction:

Accepted Answer

A)  generally increases when pH increases.
B)  increases in the presence of a competitive inhibitor.
C)  is limited only by the amount of substrate supplied.
D)  is twice the rate observed when the concentration of substrate is equal to the Km.
E)  is unchanged in the presence of a uncompetitive inhibitor.F) D) and E)
G) A) and E)

Question 5

Enzymes are potent catalysts because they:

Accepted Answer

A)  are consumed in the reactions they catalyze.
B)  are very specific and can prevent the conversion of products back to substrates.
C)  drive reactions to completion while other catalysts drive reactions to equilibrium.
D)  increase the equilibrium constants for the reactions they catalyze.
E)  lower the activation energy for the reactions they catalyze.F) A) and C)
G) A) and D)

Question 6

The double-reciprocal transformation of the Michaelis-Menten equation,also called the Lineweaver-Burk plot,is given by
1/V0 = Km /(Vmax[S]) + 1/Vmax
To determine Km from a double-reciprocal plot,you would:

Accepted Answer

A)  multiply the reciprocal of the x-axis intercept by -1.
B)  multiply the reciprocal of the y-axis intercept by -1.
C)  take the reciprocal of the x-axis intercept.
D)  take the reciprocal of the y-axis intercept.
E)  take the x-axis intercept,where V0 = 1/2 Vmax.F) B) and E)
G) A) and E)

Question 7

Fifteen $\mu$g of an enzyme of Mr 30,000 working at Vmax catalyzes the conversion of 60 $\mu$mol of substrate into product in 3 min.What is the enzyme's turnover number?

Accepted Answer

The amount of enzyme present is 15 *10<s...

Question 8

Compare the two reaction coordinate diagrams below and select the answer that correctly describes their relationship.In each case,the single intermediate is the ES complex.

Accepted Answer

A)  (a) describes a strict "lock and key" model,whereas (b) describes a transition-state complementarity model.
B)  The activation energy for the catalyzed reaction is 5 in (a) and is 7 in (b) .
C)  The activation energy for the uncatalyzed reaction is given by 5 + 6 in (a) and by 7 + 4 in (b) .
D)  The contribution of binding energy is given by 5 in (a) and by 7 in (b) .
E)  The ES complex is given by 2 in (a) and 3 in (b) .F) B) and D)
G) A) and B)

Question 9

In competitive inhibition,an inhibitor:

Accepted Answer

A)  binds at several different sites on an enzyme.
B)  binds covalently to the enzyme.
C)  binds only to the ES complex.
D)  binds reversibly at the active site.
E)  lowers the characteristic Vmax of the enzyme.F) A) and B)
G) None of the above

Question 10

On the enzyme hexokinase,ATP reacts with glucose to produce glucose 6-phosphate and ADP five orders of magnitude faster than ATP reacts with H2O to form phosphate and ADP.The intrinsic chemical reactivity of the -OH group in water is about the same as that of the glucose molecule,and water can certainly fit into the active site.Explain this rate differential in two sentences or less.

Accepted Answer

The binding of glucose to hexokinase ind...

Question 11

Sometimes the difference in (standard)free-energy content,$\Delta$G'°,between a substrate S and a product P is very large,yet the rate of chemical conversion,S $\rightarrow$ P,is quite slow.Why?

Accepted Answer

The rate of conversion from substrate to...

Question 12

Blood coagulation involves:

Accepted Answer

A)  a kinase cascade.
B)  zymogen activation.
C)  serine proteases.
D)  A and B.
E)  B and C.F) A) and E)
G) C) and D)

Question 13

The concept of "induced fit" refers to the fact that:

Accepted Answer

A)  enzyme specificity is induced by enzyme-substrate binding.
B)  enzyme-substrate binding induces an increase in the reaction entropy,thereby catalyzing the reaction.
C)  enzyme-substrate binding induces movement along the reaction coordinate to the transition state.
D)  substrate binding may induce a conformational change in the enzyme,which then brings catalytic groups into proper orientation.
E)  when a substrate binds to an enzyme,the enzyme induces a loss of water (desolvation) from the substrate.F) B) and C)
G) A) and E)

Question 14

An enzyme-catalyzed reaction was carried out with the substrate concentration initially a thousand times greater than the Km for that substrate.After 9 minutes,1% of the substrate had been converted to product,and the amount of product formed in the reaction mixture was 12  μ\muμ mol.If,in a separate experiment,one-third as much enzyme and twice as much substrate had been combined,how long would it take for the same amount (12  μ\muμ mol) of product to be formed?

Accepted Answer

A)  1) 5 min
B)  13.5 min
C)  27 min
D)  3 min
E)  6 min F) A) and E)
G) C) and D)

Question 15

In the following diagram of the first step in the reaction catalyzed by the protease chymotrypsin,the process of general base catalysis is illustrated by the number ________,and the process of covalent catalysis is illustrated by the number _________.

Accepted Answer

A)  1;2
B)  1;3
C)  2;3
D)  2 ;3
E)  3;2F) C) and E)
G) None of the above

Question 16

Which of the following has not been shown to play a role in determining the specificity of protein kinases?

Accepted Answer

A)  Disulfide bonds near the phosphorylation site
B)  Primary sequence at phosphorylation site
C)  Protein quaternary structure
D)  Protein tertiary structure
E)  Residues near the phosphorylation siteF) C) and D)
G) B) and E)

Question 17

Why is the Lineweaver-Burk (double reciprocal)plot (see Box 6,p.206)more useful than the standard V vs.[S] plot in determining kinetic constants for an enzyme? (Your answer should probably show typical plots. )

Accepted Answer

The plot of V vs.[S] is hyperbolic;maxim...

Question 18

Two different enzymes are able to catalyze the same reaction,A $\rightarrow$ B.They both have the same Vmax,but differ their Km the substrate A.For enzyme 1,the Km is 1.0 mM;for enzyme 2,the Km is 10 mM.When enzyme 1 was incubated with 0.1 mM A,it was observed that B was produced at a rate of 0.0020 mmoles/minute.
a)What is the value of the Vmax of the enzymes? 
b)What will be the rate of production of B when enzyme 2 is incubated with 0.1 mM A? 
c)What will be the rate of production of B when enzyme 1 is incubated with 1 M (i.e. ,1000 mM)A?

Accepted Answer

a)0.022 mmol/min;
b)...

Question 19

Which one of the following statements is true of enzyme catalysts?

Accepted Answer

A)  They bind to substrates but are never covalently attached to substrate or product.
B)  They increase the equilibrium constant for a reaction,thus favoring product formation.
C)  They increase the stability of the product of a desired reaction by allowing ionizations,resonance,and isomerizations not normally available to substrates.
D)  They lower the activation energy for the conversion of substrate to product.
E)  To be effective,they must be present at the same concentration as their substrates.F) A) and B)
G) A) and E)

Question 20

Phenyl-methane-sulfonyl-fluoride (PMSF) inactivates serine proteases by binding covalently to the catalytic serine residue at the active site;this enzyme-inhibitor bond is not cleaved by the enzyme.This is an example of what kind of inhibition?

Accepted Answer

A)  Irreversible
B)  Competitive
C)  Non-competitive
D)  Mixed
E)  pH inhibitionF) C) and E)
G) A) and E)

Exam 6: Enzymes

Enzymes are potent catalysts because they:

Correct Answer
verified

Phenyl-methane-sulfonyl-fluoride (PMSF) inactivates serine proteases by binding covalently to the catalytic serine residue at the active site;this enzyme-inhibitor bond is not cleaved by the enzyme.This is an example of what kind of inhibition?

Correct Answer
verified

Correct Answer
verified
Only V_max and...
View Answer

Fifteen $\mu$ g of an enzyme of M_r 30,000 working at V_max catalyzes the conversion of 60 $\mu$ mol of substrate into product in 3 min.What is the enzyme's turnover number?

Correct Answer
verified
The amount of enzyme present is 15 *10
View Answer

Blood coagulation involves:

Correct Answer
verified

Sometimes the difference in (standard)free-energy content, $\Delta$ G'°,between a substrate S and a product P is very large,yet the rate of chemical conversion,S $\rightarrow$ P,is quite slow.Why?

Correct Answer
verified
The rate of conversion from substrate to...
View Answer

Which of the following has not been shown to play a role in determining the specificity of protein kinases?

Correct Answer
verified

Which one of the following statements is true of enzyme catalysts?

Correct Answer
verified

Compare the two reaction coordinate diagrams below and select the answer that correctly describes their relationship.In each case,the single intermediate is the ES complex.

Correct Answer
verified

V_max for an enzyme-catalyzed reaction:

Correct Answer
verified

In competitive inhibition,an inhibitor:

Correct Answer
verified

The double-reciprocal transformation of the Michaelis-Menten equation,also called the Lineweaver-Burk plot,is given by 1/V₀ = K_m /(V_max[S]) + 1/V_max To determine K_m from a double-reciprocal plot,you would:

Correct Answer
verified

Correct Answer
verified
The binding of glucose to hexokinase ind...
View Answer

Define the term "suicide inhibitor."

Correct Answer
verified
A suicide inhibitor is a molecule that i...
View Answer

Why is the Lineweaver-Burk (double reciprocal)plot (see Box 6,p.206)more useful than the standard V vs.[S] plot in determining kinetic constants for an enzyme? (Your answer should probably show typical plots. )

Correct Answer
verified
The plot of V vs.[S] is hyperbolic;maxim...
View Answer

Correct Answer
verified
a)0.022 mmol/min;
b)...
View Answer

Correct Answer
verified

To calculate the turnover number of an enzyme,you need to know:

Correct Answer
verified

The concept of "induced fit" refers to the fact that:

Correct Answer
verified

In the following diagram of the first step in the reaction catalyzed by the protease chymotrypsin,the process of general base catalysis is illustrated by the number ,and the process of covalent catalysis is illustrated by the number _.

Correct Answer
verified

Exam 6: Enzymes

Enzymes are potent catalysts because they:

Correct AnswerverifiedShow Answer

Phenyl-methane-sulfonyl-fluoride (PMSF) inactivates serine proteases by binding covalently to the catalytic serine residue at the active site;this enzyme-inhibitor bond is not cleaved by the enzyme.This is an example of what kind of inhibition?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedOnly Vmax and...View AnswerShow Answer

Fifteen μ\muμ g of an enzyme of Mr 30,000 working at Vmax catalyzes the conversion of 60 μ\muμ mol of substrate into product in 3 min.What is the enzyme's turnover number?

Correct AnswerverifiedThe amount of enzyme present is 15 *10View AnswerShow Answer

Blood coagulation involves:

Correct AnswerverifiedShow Answer

Sometimes the difference in (standard)free-energy content, Δ\DeltaΔ G'°,between a substrate S and a product P is very large,yet the rate of chemical conversion,S →\rightarrow→ P,is quite slow.Why?

Correct AnswerverifiedThe rate of conversion from substrate to...View AnswerShow Answer

Which of the following has not been shown to play a role in determining the specificity of protein kinases?

Correct AnswerverifiedShow Answer

Which one of the following statements is true of enzyme catalysts?

Correct AnswerverifiedShow Answer

Compare the two reaction coordinate diagrams below and select the answer that correctly describes their relationship.In each case,the single intermediate is the ES complex.

Correct AnswerverifiedShow Answer

Vmax for an enzyme-catalyzed reaction:

Correct AnswerverifiedShow Answer

In competitive inhibition,an inhibitor:

Correct AnswerverifiedShow Answer

The double-reciprocal transformation of the Michaelis-Menten equation,also called the Lineweaver-Burk plot,is given by 1/V0 = Km /(Vmax[S]) + 1/Vmax To determine Km from a double-reciprocal plot,you would:

Correct AnswerverifiedShow Answer

Correct AnswerverifiedThe binding of glucose to hexokinase ind...View AnswerShow Answer

Define the term "suicide inhibitor."

Correct AnswerverifiedA suicide inhibitor is a molecule that i...View AnswerShow Answer

Why is the Lineweaver-Burk (double reciprocal)plot (see Box 6,p.206)more useful than the standard V vs.[S] plot in determining kinetic constants for an enzyme? (Your answer should probably show typical plots. )

Correct AnswerverifiedThe plot of V vs.[S] is hyperbolic;maxim...View AnswerShow Answer

Correct Answerverifieda)0.022 mmol/min;b)...View AnswerShow Answer

Correct AnswerverifiedShow Answer

To calculate the turnover number of an enzyme,you need to know:

Correct AnswerverifiedShow Answer

The concept of "induced fit" refers to the fact that:

Correct AnswerverifiedShow Answer

In the following diagram of the first step in the reaction catalyzed by the protease chymotrypsin,the process of general base catalysis is illustrated by the number ________,and the process of covalent catalysis is illustrated by the number _________.

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Only V_max and...
View Answer

Fifteen $\mu$ g of an enzyme of M_r 30,000 working at V_max catalyzes the conversion of 60 $\mu$ mol of substrate into product in 3 min.What is the enzyme's turnover number?

Correct Answer
verified
The amount of enzyme present is 15 *10
View Answer

Correct Answer
verified

Sometimes the difference in (standard)free-energy content, $\Delta$ G'°,between a substrate S and a product P is very large,yet the rate of chemical conversion,S $\rightarrow$ P,is quite slow.Why?

Correct Answer
verified
The rate of conversion from substrate to...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

V_max for an enzyme-catalyzed reaction:

Correct Answer
verified

Correct Answer
verified

The double-reciprocal transformation of the Michaelis-Menten equation,also called the Lineweaver-Burk plot,is given by 1/V₀ = K_m /(V_max[S]) + 1/V_max To determine K_m from a double-reciprocal plot,you would:

Correct Answer
verified

Correct Answer
verified
The binding of glucose to hexokinase ind...
View Answer

Correct Answer
verified
A suicide inhibitor is a molecule that i...
View Answer

Correct Answer
verified
The plot of V vs.[S] is hyperbolic;maxim...
View Answer

Correct Answer
verified
a)0.022 mmol/min;
b)...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

In the following diagram of the first step in the reaction catalyzed by the protease chymotrypsin,the process of general base catalysis is illustrated by the number ,and the process of covalent catalysis is illustrated by the number _.

Correct Answer
verified