Biochemistry Exam 2 Questions with 100% Correct
Solutions
Which of the following statements about enzymes are true:
1. Catalysis occurs at the active site, which usually consists of a crevice on the surface
of the enzyme.
2. Generally, an enzyme is specific for a particular substrate. For example, thrombin
catalyzes the hydrolysis of the peptide bond between Arg and Gly.
3. An enzyme yields a specific product, whereas a nonbiological catalyst may produce
more than one product, and side reactions may occur.
4. Nonbiological catalysts and enzymes tend to have a similar degree of reaction
specificity.
5. A substrate must bind to the active site before catalysis can occur.
1,2,3,5
general enzyme-catalyzed reaction.
E + S ↔ ES ↔ E + P
What effects are produced by an enzyme on the general reaction below
S↔P
k1→
k2←
2. the activation energy for the reaction is lowered.
3. the rate constant for the reverse reaction (k2) increases.
4. ∆G for the reaction decreases.
,5. The formation of the transition state is promoted.
6.The concentration of the products is increased.
2,3,5
Which of the following interactions can contribute to the intrinsic binding energy
during enzymatic catalysis:
1. permanent covalent bonding
2. electrostatic interactions
3. nucleophilic attack by serine
4. hydrogen bonding
5. van der waals interactions
2, 4, 5
sort the following into: acid-base catalysis, covalent catalysis, metal ion catalysis, or
all.
1. catalyst retains its original form after reaction occurs.
2. a proton is transferred between enzyme and substrate.
3. a covalent bond forms between enzyme and substrate.
4. may use amino acids such as aspartate or lysine for protonation or proton
abstraction.
5. may take part in interactions involving Fe2+.
6. Catalysts may participate in oxidation-reduction reactions by changes in the
oxidation state.
7. uses a nucleophilic function group.
8. lowers the energy or stabilizes the transition state or intermediate.
9. a Zn2+ cofactor may properly orient the substrate in the active site through ionic
, interactions.
10. two-part catalytic process(for example, the chymotrypsin mechanism).
acid-base catalysis: 2, 4
covalent catalysis: 3, 7, 10
metal ion catalysis: 5,6,9
all: 8, 1
suppose that an arginine residue in the active site of an enzyme was mutated to
alanine. as expected, the alanine mutant was inactive, suggesting that the arginine
residue was critical to the catalytic mechanism.
which mutantion is most likely to restore wild-type level of activity to the alanine
mutant.
a to e
a to k
a to m
a to y
a to s
A TO K
sort the following into lock-and-key model, induced-fit model, or common to both.
1. substrate binds to the enyzme at the active site, forming an enzyme-substrate
complex.
2.enzyme active site has a rigid structure complementary to that of the substrate.
Solutions
Which of the following statements about enzymes are true:
1. Catalysis occurs at the active site, which usually consists of a crevice on the surface
of the enzyme.
2. Generally, an enzyme is specific for a particular substrate. For example, thrombin
catalyzes the hydrolysis of the peptide bond between Arg and Gly.
3. An enzyme yields a specific product, whereas a nonbiological catalyst may produce
more than one product, and side reactions may occur.
4. Nonbiological catalysts and enzymes tend to have a similar degree of reaction
specificity.
5. A substrate must bind to the active site before catalysis can occur.
1,2,3,5
general enzyme-catalyzed reaction.
E + S ↔ ES ↔ E + P
What effects are produced by an enzyme on the general reaction below
S↔P
k1→
k2←
2. the activation energy for the reaction is lowered.
3. the rate constant for the reverse reaction (k2) increases.
4. ∆G for the reaction decreases.
,5. The formation of the transition state is promoted.
6.The concentration of the products is increased.
2,3,5
Which of the following interactions can contribute to the intrinsic binding energy
during enzymatic catalysis:
1. permanent covalent bonding
2. electrostatic interactions
3. nucleophilic attack by serine
4. hydrogen bonding
5. van der waals interactions
2, 4, 5
sort the following into: acid-base catalysis, covalent catalysis, metal ion catalysis, or
all.
1. catalyst retains its original form after reaction occurs.
2. a proton is transferred between enzyme and substrate.
3. a covalent bond forms between enzyme and substrate.
4. may use amino acids such as aspartate or lysine for protonation or proton
abstraction.
5. may take part in interactions involving Fe2+.
6. Catalysts may participate in oxidation-reduction reactions by changes in the
oxidation state.
7. uses a nucleophilic function group.
8. lowers the energy or stabilizes the transition state or intermediate.
9. a Zn2+ cofactor may properly orient the substrate in the active site through ionic
, interactions.
10. two-part catalytic process(for example, the chymotrypsin mechanism).
acid-base catalysis: 2, 4
covalent catalysis: 3, 7, 10
metal ion catalysis: 5,6,9
all: 8, 1
suppose that an arginine residue in the active site of an enzyme was mutated to
alanine. as expected, the alanine mutant was inactive, suggesting that the arginine
residue was critical to the catalytic mechanism.
which mutantion is most likely to restore wild-type level of activity to the alanine
mutant.
a to e
a to k
a to m
a to y
a to s
A TO K
sort the following into lock-and-key model, induced-fit model, or common to both.
1. substrate binds to the enyzme at the active site, forming an enzyme-substrate
complex.
2.enzyme active site has a rigid structure complementary to that of the substrate.
