Enzymes MCQs

1. Enzymes are primarily composed of:
A) Lipids
B) Proteins
C) Carbohydrates
D) Nucleic acids
Answer: B) Proteins
The region where substrate binds on an enzyme is called:
A) Active site
B) Binding pocket
C) Reaction center
D) Catalytic groove
Answer: A) Active site
Enzymes function by:
A) Increasing activation energy
B) Decreasing activation energy
C) Increasing temperature
D) Changing pH
Answer: B) Decreasing activation energy
Which model explains enzyme-substrate interaction?
A) Fluid mosaic model
B) Lock and key model
C) Bohr model
D) Atomic model
Answer: B) Lock and key model
Enzymes are:
A) Consumed in reactions
B) Not reusable
C) Biological catalysts
D) Structural molecules
Answer: C) Biological catalysts
Which factor does NOT affect enzyme activity?
A) Temperature
B) pH
C) Light
D) Substrate concentration
Answer: C) Light
The optimal temperature for most human enzymes is:
A) 25°C
B) 37°C
C) 50°C
D) 100°C
Answer: B) 37°C
Denaturation of enzymes occurs due to:
A) Low substrate
B) High temperature
C) Low pressure
D) Neutral pH
Answer: B) High temperature
Enzymes are specific because of their:
A) Shape
B) Size
C) Weight
D) Color
Answer: A) Shape
The substrate is:
A) Product
B) Reactant
C) Enzyme
D) Catalyst
Answer: B) Reactant
Which enzyme breaks down starch?
A) Protease
B) Lipase
C) Amylase
D) Lactase
Answer: C) Amylase
Enzymes speed up reactions by:
A) Changing products
B) Lowering activation energy
C) Increasing pressure
D) Increasing volume
Answer: B) Lowering activation energy
The product is formed after:
A) Enzyme binding
B) Reaction completion
C) Substrate formation
D) Activation energy increase
Answer: B) Reaction completion
Coenzymes are:
A) Protein parts
B) Non-protein helpers
C) Enzymes
D) Substrates
Answer: B) Non-protein helpers
Apoenzyme + cofactor =
A) Holoenzyme
B) Isoenzyme
C) Zymogen
D) Substrate
Answer: A) Holoenzyme
Competitive inhibitors:
A) Bind to active site
B) Bind elsewhere
C) Increase reaction
D) Destroy enzyme
Answer: A) Bind to active site
Non-competitive inhibitors bind to:
A) Active site
B) Allosteric site
C) Substrate
D) Product
Answer: B) Allosteric site
Enzymes are highly:
A) Non-specific
B) Specific
C) Random
D) Variable
Answer: B) Specific
Which enzyme digests proteins?
A) Amylase
B) Lipase
C) Protease
D) Maltase
Answer: C) Protease
The pH optimum of pepsin is:
A) Neutral
B) Acidic
C) Basic
D) Variable
Answer: B) Acidic
The pH optimum of trypsin is:
A) Acidic
B) Neutral
C) Basic
D) Zero
Answer: C) Basic
Enzymes are affected by:
A) Temperature
B) pH
C) Concentration
D) All of these
Answer: D) All of these
The substance on which enzyme acts is:
A) Product
B) Substrate
C) Catalyst
D) Enzyme
Answer: B) Substrate
Enzyme activity increases with temperature until:
A) Denaturation
B) Freezing
C) Boiling
D) Cooling
Answer: A) Denaturation
Which vitamin acts as coenzyme?
A) Vitamin C
B) Vitamin B
C) Vitamin D
D) Vitamin A
Answer: B) Vitamin B
The study of enzymes is called:
A) Biology
B) Enzymology
C) Zoology
D) Botany
Answer: B) Enzymology
Enzymes are mostly found in:
A) Cytoplasm
B) Nucleus
C) Cell wall
D) Membrane
Answer: A) Cytoplasm
The enzyme-substrate complex is:
A) Temporary
B) Permanent
C) Stable
D) Irreversible
Answer: A) Temporary
The shape of enzyme changes during:
A) Lock model
B) Induced fit model
C) Static model
D) Linear model
Answer: B) Induced fit model
Enzyme action is reversible when:
A) Conditions allow
B) Temperature high
C) Pressure low
D) Substrate absent
Answer: A) Conditions allow
The rate of enzyme reaction depends on:
A) Substrate concentration
B) Enzyme concentration
C) Temperature
D) All of these
Answer: D) All of these
Which enzyme breaks lipids?
A) Amylase
B) Lipase
C) Protease
D) Lactase
Answer: B) Lipase
Enzymes lower activation energy by:
A) Increasing heat
B) Stabilizing transition state
C) Increasing substrate
D) Increasing pressure
Answer: B) Stabilizing transition state
Enzyme saturation occurs when:
A) All active sites filled
B) No substrate
C) Enzyme destroyed
D) Temperature low
Answer: A) All active sites filled
The graph of enzyme activity vs temperature is:
A) Linear
B) Bell-shaped
C) Flat
D) Exponential
Answer: B) Bell-shaped
Enzymes can be reused because they are:
A) Permanent
B) Unchanged after reaction
C) Destroyed
D) Reactants
Answer: B) Unchanged after reaction
Which enzyme breaks lactose?
A) Maltase
B) Lactase
C) Lipase
D) Protease
Answer: B) Lactase
Enzymes are affected by heavy metals because:
A) They bind enzymes
B) Increase activity
C) Reduce substrate
D) Increase pH
Answer: A) They bind enzymes
Inhibition reduces:
A) Activity
B) Temperature
C) pH
D) Pressure
Answer: A) Activity
Irreversible inhibitors:
A) Permanently disable enzyme
B) Temporary effect
C) Increase reaction
D) None
Answer: A) Permanently disable enzyme
Enzymes are named by:
A) Adding “-ase”
B) Adding “-in”
C) Adding “-ol”
D) Adding “-gen”
Answer: A) Adding “-ase”
Catalase breaks:
A) H₂O₂
B) Glucose
C) Lipids
D) Proteins
Answer: A) H₂O₂
Zymogens are:
A) Active enzymes
B) Inactive precursors
C) Substrates
D) Products
Answer: B) Inactive precursors
Enzyme activity is highest at:
A) Optimal conditions
B) Low temp
C) High pressure
D) Neutral always
Answer: A) Optimal conditions
Which is NOT enzyme property?
A) Specific
B) Reusable
C) Consumed
D) Catalytic
Answer: C) Consumed
Enzymes in saliva:
A) Lipase
B) Amylase
C) Protease
D) Pepsin
Answer: B) Amylase
Turnover number refers to:
A) Rate of enzyme action
B) Enzyme size
C) pH
D) Temperature
Answer: A) Rate of enzyme action
Allosteric enzymes have:
A) Single site
B) Multiple sites
C) No site
D) One substrate
Answer: B) Multiple sites
Feedback inhibition involves:
A) Product inhibiting enzyme
B) Substrate inhibiting
C) Enzyme destroyed
D) Temperature effect
Answer: A) Product inhibiting enzyme
50. Enzyme kinetics studies:
A) Speed of reactions
B) Shape
C) Size
D) Structure
Answer: A) Speed of reactions