Question 1

Which of the following is true regarding heparin?

Accepted Answer

A)   it is an allosteric activator of antithrombin
B)   it is a sulfated polysaccharide
C)   it simultaneously binds to antithrombin and the target of antithrombin
D)   it is used clinically as an anticoagulant
E)   all of the above E

Question 2

Which of the following is a feature of protease inhibitor specific for trypsin?

Accepted Answer

A)   contains a positive charge to mimic the charge of the substrate
B)   ability to interact with the Ser of the catalytic triad
C)   inability to form the tetrahedral intermediate
D)   high affinity for the enzyme active site
E)   all of the above E

Question 3

Different enzymes that catalyze the same reaction are known as _____.

Accepted Answer

A)   transferases
B)   isomerases
C)   allosteric enzymes
D)   holoenzymes
E)   isozymes E

Question 4

In an enzyme mechanism that generates a negative charge in the transition state, which of the following would be most effective to have in the active site of the enzyme?

Accepted Answer

A)   transition metal cation
B)   Asp residue
C)   Gln residue
D)   transition metal anion
E)   none of the above

Question 5

An organic molecule that is tightly bound to an enzyme and participates in an enzyme catalyzed reaction is specifically referred to as a _____.

Accepted Answer

A)   cofactor
B)   metal ion
C)   coenzyme
D)   cosubstrate
E)   prosthetic group

Question 6

Zymogens are not enzymatically active because _____.

Accepted Answer

A)   they do not contain the cofactors required for catalysis
B)   they are the product of mutated genes
C)   their active sites are distorted and incapable of enzymatic activity
D)   the pH of their environment is not optimal for activity
E)   none of the above

Question 7

Thrombin is similar to ___ as it cleaves peptide bonds following ___ residues.

Accepted Answer

The answer of Thrombin is similar to ___ as it...

Question 8

In the enzyme catalyzed decarboxylation of acetoacetate, a Schiff base is formed between the ketone of acetoacetate and a _____ residue in the active site of the enzyme.

Accepted Answer

A)   Arg
B)   Asn
C)   Lys
D)   Glu
E)   Ser

Question 9

If an enzyme rate increases 10-fold for every 5.7 kJ/mol decrease in the energy of activation, what rate increase would be observed if three H-bonds were stabilizing the transition state with each H-bond having a strength of 21 kJ/mol?

Accepted Answer

A)   11-fold increase
B)   37-fold increase
C)   60-fold increase
D)   100-fold increase
E)   1011-fold increase

Question 10

Of the following ions, which would be most likely to participate in metal ion catalysis?

Accepted Answer

A)   Na+
B)   Zn2+
C)   Ag+
D)   K+
E)   Ba2+

Question 11

Of all the species that enzymes bind, they are thought to bind most tightly to _____.

Accepted Answer

A)   substrates
B)   products
C)   transition states
D)   intermediates
E)   all are bound very tightly

Question 12

The ability for an enzyme to pick out one particular substrate from the myriad of molecules floating around its environment is an example of _____.

Accepted Answer

A)   natural selection
B)   specificity
C)   high affinity
D)   processivity
E)   none of the above

Question 13

The enzyme hexokinase catalyzes a reaction where its substrates are completely sequestered from the aqueous environment allowing for interactions to occur between enzyme and substrates that would not normally occur in an aqueous environment. What term describes this type of catalysis?

Accepted Answer

A)   electrostatic catalysis
B)   desolvation catalysis
C)   non-aqueous catalysis
D)   hydrogen-bonded catalysis
E)   closed-system catalysis

Question 14

The blood coagulation cascade is triggered when ___ is converted to ___.

Accepted Answer

The answer of The blood coagulation cascade is triggered when...

Question 15

How does a catalyst increase the rate of a reaction?

Accepted Answer

A)   It makes the reaction more exergonic.
B)   It increases the temperature of the reaction.
C)   It allows reacting molecules to more easily form the transition state.
D)   It causes a localized increase in the concentration of reactants.
E)   None of the above

Question 16

How does a catalyst increase the rate of a reaction?

Accepted Answer

A)   it makes the reaction more exergonic
B)   it increases the temperature of the reaction
C)   it allows reacting molecules to more easily form the transition state
D)   it causes a localized increase in the concentration of reactants
E)   none of the above

Question 17

Thrombin circulates in the blood as a(n) ___ that is called ___.

Accepted Answer

The answer of Thrombin circulates in the blood as a(n)...

Question 18

Fibrinogen is converted to _____ by the action of _____.

Accepted Answer

The answer of Fibrinogen is converted to _____ by the...

Question 19

Which protein in the blood is responsible for converting fibrinogen to fibrin?

Accepted Answer

A)   thrombin
B)   factor X
C)   factor VII
D)   factor VIIa
E)   prothrombin

Question 20

Conversion of factor X to factor Xa represents a(n) _____ form of activation; binding of antithrombin to thrombin represents a(n) _____ form of inhibition.

Accepted Answer

A)   reversible; reversible
B)   irreversible; reversible
C)   reversible; irreversible
D)   irreversible; irreversible
E)   none of the above since antithrombin is not an inhibitor of thrombin

Exam 6: How Enzymes Work

Which of the following is true regarding heparin?

Which of the following is a feature of protease inhibitor specific for trypsin?

Different enzymes that catalyze the same reaction are known as _____.

In an enzyme mechanism that generates a negative charge in the transition state, which of the following would be most effective to have in the active site of the enzyme?

An organic molecule that is tightly bound to an enzyme and participates in an enzyme catalyzed reaction is specifically referred to as a _____.

Zymogens are not enzymatically active because _____.

Thrombin is similar to _ as it cleaves peptide bonds following _ residues.

In the enzyme catalyzed decarboxylation of acetoacetate, a Schiff base is formed between the ketone of acetoacetate and a _____ residue in the active site of the enzyme.

If an enzyme rate increases 10-fold for every 5.7 kJ/mol decrease in the energy of activation, what rate increase would be observed if three H-bonds were stabilizing the transition state with each H-bond having a strength of 21 kJ/mol?

Of the following ions, which would be most likely to participate in metal ion catalysis?

Of all the species that enzymes bind, they are thought to bind most tightly to _____.

The ability for an enzyme to pick out one particular substrate from the myriad of molecules floating around its environment is an example of _____.

The enzyme hexokinase catalyzes a reaction where its substrates are completely sequestered from the aqueous environment allowing for interactions to occur between enzyme and substrates that would not normally occur in an aqueous environment. What term describes this type of catalysis?

The blood coagulation cascade is triggered when _ is converted to _.

How does a catalyst increase the rate of a reaction?

How does a catalyst increase the rate of a reaction?

Thrombin circulates in the blood as a(n) _ that is called _.

Fibrinogen is converted to _ by the action of _.

Which protein in the blood is responsible for converting fibrinogen to fibrin?

Conversion of factor X to factor Xa represents a(n) _ form of activation; binding of antithrombin to thrombin represents a(n) _ form of inhibition.