Enzyme
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Organized
MCQ Compilation
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Dr. Mohamed Khomsi
Fb: دمحم الخمسي.د
Feb / 2019
1
, : اسئلة السمسترات الماضية
1. The tear secretion contains an antibacterial enzyme known as : )2 (مفاضلة
a) Zymase
b) Asparaginase
c) Lysozymes (c)
d) Lipase
e) Plasmin
2. Feedback term refers to : )2 (مفاضلة
a) Effect of substrate on rate of enzymatic reaction
b) Effect of end product on rate of reaction
c) Effect on enzyme concentration on rate of reaction (b)
d) Effect on external compound on rate of reaction
e) None of the above
3. Which one of the following regulatory actions involves a reversible covalent
modification of the enzyme : )2 (مفاضلة
a) Phosphorylation of Ser-OH on the enzyme
b) Allostertic modulation
c) Competitive inhibition (a)
d) Noncompetitive inhibition
e) a and c
4. If the substrate concentration is much below the Km of the enzyme , the velocity of
the reaction is : )2 (مفاضلة
a) Directly proportional to substrate concentration
b) Not affected by enzyme concentration
c) Nearly equal to Vmax (a)
d) inversibly proportional to substrate concentration
e) A and B only
5. Which of the following is a proenzyme: )2 (مفاضلة
a) Carboxypeptidase
b) Aminopeptidase
c) Chymotrypsin (e)
d) Pepsinogen
e) Plasminogen
2
, 6. Enzyme increase the rate of reactions by : )2 (مفاضلة
a) Increasing the free energy of activation
b) Decreasing the energy of activation
c) Increasing the equilibrium constant of the reaction (b)
d) Increasing the free energy of the reaction
e) None of the above
7. In non-competitive inhibition which of the following kinetic effect is true : )2 (مفاضلة
a) Decrease both Km and Vmax
b) Increase both Km and Vmax
c) Decrease Km without effecting Vmax (e)
d) Increases Km without affecting Vmax
e) Decreases Vmax without affecting Km
8. Lock and key model of enzyme action proposed by fisher implies that : )2 (مفاضلة
a) The active site is flexible and adjusts to substrate
b) The active site requires the removel of Po4 group
c) The active site is complementary in shape to that substrate (c)
d) Substrate change conformation prior to active site interaction
e) None of the above
9. Maximum enzyme activity is observed at : )2 (مفاضلة
a) Acidic pH
b) Basic pH
c) Neutral pH (e)
d) Acidic and Basic
e) Optimum pH
10. Conversion of pyruvate into acetyl CoA is catalyzed by : )2 (مفاضلة
a) Pyruvate dehydrogenase
b) Dihydrolipoyl acetyl Transferase
c) Dihydrolipoyl dehydrogenase (d)
d) All the 3 acting in concert
e) None of the above
11. Different Isoenzyme of an enzyme have the same : )2 (مفاضلة
a) Amino acid sequence
b) Michael’s constant
c) Catalytic activity (c)
d) A and B only
e) All of the above
3
.
.
.
Organized
MCQ Compilation
.
.
.
Dr. Mohamed Khomsi
Fb: دمحم الخمسي.د
Feb / 2019
1
, : اسئلة السمسترات الماضية
1. The tear secretion contains an antibacterial enzyme known as : )2 (مفاضلة
a) Zymase
b) Asparaginase
c) Lysozymes (c)
d) Lipase
e) Plasmin
2. Feedback term refers to : )2 (مفاضلة
a) Effect of substrate on rate of enzymatic reaction
b) Effect of end product on rate of reaction
c) Effect on enzyme concentration on rate of reaction (b)
d) Effect on external compound on rate of reaction
e) None of the above
3. Which one of the following regulatory actions involves a reversible covalent
modification of the enzyme : )2 (مفاضلة
a) Phosphorylation of Ser-OH on the enzyme
b) Allostertic modulation
c) Competitive inhibition (a)
d) Noncompetitive inhibition
e) a and c
4. If the substrate concentration is much below the Km of the enzyme , the velocity of
the reaction is : )2 (مفاضلة
a) Directly proportional to substrate concentration
b) Not affected by enzyme concentration
c) Nearly equal to Vmax (a)
d) inversibly proportional to substrate concentration
e) A and B only
5. Which of the following is a proenzyme: )2 (مفاضلة
a) Carboxypeptidase
b) Aminopeptidase
c) Chymotrypsin (e)
d) Pepsinogen
e) Plasminogen
2
, 6. Enzyme increase the rate of reactions by : )2 (مفاضلة
a) Increasing the free energy of activation
b) Decreasing the energy of activation
c) Increasing the equilibrium constant of the reaction (b)
d) Increasing the free energy of the reaction
e) None of the above
7. In non-competitive inhibition which of the following kinetic effect is true : )2 (مفاضلة
a) Decrease both Km and Vmax
b) Increase both Km and Vmax
c) Decrease Km without effecting Vmax (e)
d) Increases Km without affecting Vmax
e) Decreases Vmax without affecting Km
8. Lock and key model of enzyme action proposed by fisher implies that : )2 (مفاضلة
a) The active site is flexible and adjusts to substrate
b) The active site requires the removel of Po4 group
c) The active site is complementary in shape to that substrate (c)
d) Substrate change conformation prior to active site interaction
e) None of the above
9. Maximum enzyme activity is observed at : )2 (مفاضلة
a) Acidic pH
b) Basic pH
c) Neutral pH (e)
d) Acidic and Basic
e) Optimum pH
10. Conversion of pyruvate into acetyl CoA is catalyzed by : )2 (مفاضلة
a) Pyruvate dehydrogenase
b) Dihydrolipoyl acetyl Transferase
c) Dihydrolipoyl dehydrogenase (d)
d) All the 3 acting in concert
e) None of the above
11. Different Isoenzyme of an enzyme have the same : )2 (مفاضلة
a) Amino acid sequence
b) Michael’s constant
c) Catalytic activity (c)
d) A and B only
e) All of the above
3
