Enzymes MCQs

51. Isoenzymes are:
A) Different enzymes with same function
B) Same enzymes with different functions
C) Inactive enzymes
D) Denatured enzymes
Answer: A) Different enzymes with same function
The active site is complementary to:
A) Product
B) Substrate
C) Enzyme
D) Cofactor
Answer: B) Substrate
Enzyme specificity is due to:
A) Chemical composition
B) Shape of active site
C) Size of enzyme
D) Location
Answer: B) Shape of active site
The energy barrier for a reaction is called:
A) Free energy
B) Activation energy
C) Kinetic energy
D) Potential energy
Answer: B) Activation energy
Enzymes increase reaction rate by:
A) Changing equilibrium
B) Lowering activation energy
C) Increasing substrate
D) Decreasing temperature
Answer: B) Lowering activation energy
Which enzyme works in acidic pH?
A) Trypsin
B) Pepsin
C) Amylase
D) Lipase
Answer: B) Pepsin
Which enzyme works in alkaline pH?
A) Pepsin
B) Trypsin
C) Catalase
D) Amylase
Answer: B) Trypsin
Prosthetic groups are:
A) Loosely bound cofactors
B) Tightly bound cofactors
C) Substrates
D) Products
Answer: B) Tightly bound cofactors
Which is an example of coenzyme?
A) NAD⁺
B) DNA
C) RNA
D) ATP
Answer: A) NAD⁺
Enzyme activity doubles with every 10°C rise until:
A) Freezing
B) Optimum temperature
C) Denaturation
D) Neutral point
Answer: C) Denaturation
Which factor increases enzyme activity?
A) High inhibitor concentration
B) Optimal pH
C) Extreme temperature
D) Heavy metals
Answer: B) Optimal pH
Competitive inhibition can be overcome by:
A) Increasing enzyme
B) Increasing substrate
C) Decreasing temperature
D) Adding inhibitor
Answer: B) Increasing substrate
Enzyme concentration increase leads to:
A) Decreased reaction
B) Increased reaction rate
C) No change
D) Denaturation
Answer: B) Increased reaction rate
The rate of reaction is maximum when:
A) Enzyme saturated
B) No substrate
C) Low temp
D) Inhibitors present
Answer: A) Enzyme saturated
Enzyme-substrate complex formation is:
A) Permanent
B) Temporary
C) Irreversible
D) Slow
Answer: B) Temporary
Which enzyme is involved in DNA replication?
A) DNA polymerase
B) Lipase
C) Amylase
D) Protease
Answer: A) DNA polymerase
Enzymes involved in digestion are:
A) Structural enzymes
B) Metabolic enzymes
C) Digestive enzymes
D) Synthetic enzymes
Answer: C) Digestive enzymes
Which is NOT a digestive enzyme?
A) Amylase
B) Pepsin
C) Insulin
D) Lipase
Answer: C) Insulin
Insulin is:
A) Enzyme
B) Hormone
C) Cofactor
D) Substrate
Answer: B) Hormone
Ribozymes are:
A) Protein enzymes
B) RNA enzymes
C) DNA enzymes
D) Lipid enzymes
Answer: B) RNA enzymes
The enzyme urease acts on:
A) Glucose
B) Urea
C) Protein
D) Lipid
Answer: B) Urea
Enzyme inhibition can be:
A) Reversible
B) Irreversible
C) Both
D) None
Answer: C) Both
Which enzyme breaks hydrogen peroxide?
A) Lipase
B) Catalase
C) Amylase
D) Protease
Answer: B) Catalase
Enzyme action is affected by ionic strength because:
A) It changes structure
B) Changes color
C) Changes size
D) Changes pressure
Answer: A) It changes structure
Allosteric regulation occurs at:
A) Active site
B) Allosteric site
C) Substrate
D) Product
Answer: B) Allosteric site
The term “lock and key” was proposed by:
A) Darwin
B) Fischer
C) Mendel
D) Watson
Answer: B) Fischer
Induced fit model was proposed by:
A) Fischer
B) Koshland
C) Darwin
D) Mendel
Answer: B) Koshland
The enzyme hexokinase acts on:
A) Lipids
B) Glucose
C) Proteins
D) DNA
Answer: B) Glucose
ATP is important in enzyme reactions as:
A) Energy source
B) Enzyme
C) Cofactor
D) Substrate
Answer: A) Energy source
Enzyme activity decreases after optimum temperature due to:
A) Increased energy
B) Denaturation
C) Cooling
D) Reaction speed
Answer: B) Denaturation
Enzymes are affected by pH because:
A) It alters active site charge
B) It increases size
C) It changes weight
D) It increases number
Answer: A) It alters active site charge
Which is an example of oxidoreductase?
A) Lipase
B) Dehydrogenase
C) Protease
D) Amylase
Answer: B) Dehydrogenase
Transferases transfer:
A) Electrons
B) Functional groups
C) Water
D) Energy
Answer: B) Functional groups
Hydrolases catalyze:
A) Oxidation
B) Hydrolysis
C) Reduction
D) Transfer
Answer: B) Hydrolysis
Lyases break bonds without:
A) Water
B) Oxygen
C) Nitrogen
D) Energy
Answer: A) Water
Ligases join molecules using:
A) Heat
B) ATP
C) Light
D) Pressure
Answer: B) ATP
Isomerases catalyze:
A) Bond breaking
B) Rearrangement
C) Hydrolysis
D) Oxidation
Answer: B) Rearrangement
The enzyme pepsinogen is:
A) Active
B) Inactive
C) Cofactor
D) Product
Answer: B) Inactive
Enzyme specificity can be:
A) Absolute
B) Group
C) Optical
D) All of these
Answer: D) All of these
Turnover number indicates:
A) Number of substrate molecules converted per second
B) Enzyme weight
C) Temperature
D) pH
Answer: A) Number of substrate molecules converted per second
The Michaelis constant (Km) indicates:
A) Enzyme efficiency
B) Substrate affinity
C) Temperature
D) Pressure
Answer: B) Substrate affinity
Low Km means:
A) Low affinity
B) High affinity
C) No reaction
D) Denaturation
Answer: B) High affinity
High Km means:
A) High affinity
B) Low affinity
C) No substrate
D) No enzyme
Answer: B) Low affinity
Vmax represents:
A) Maximum reaction rate
B) Minimum rate
C) pH
D) Temperature
Answer: A) Maximum reaction rate
Enzymes are regulated by:
A) Inhibitors
B) Activators
C) Feedback
D) All of these
Answer: D) All of these
Cofactors may be:
A) Metal ions
B) Organic molecules
C) Both
D) None
Answer: C) Both
Which metal acts as cofactor?
A) Zn²⁺
B) Na⁺
C) K⁺
D) Cl⁻
Answer: A) Zn²⁺
Enzyme inhibition is useful in:
A) Medicine
B) Agriculture
C) Industry
D) All of these
Answer: D) All of these
Enzymes in industry are used for:
A) Food production
B) Detergents
C) Pharmaceuticals
D) All of these
Answer: D) All of these
100. Enzymes are essential for life because they:
A) Speed up metabolism
B) Store energy
C) Form tissues
D) Provide structure
Answer: A) Speed up metabolism