Enzymes — NEET Biology MCQs with Solutions
Free NEET Biology Enzymes MCQs with step-by-step solutions (6 questions). Part of Biomolecules. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Enzymes · easy · theory
Enzymes are biological catalysts that speed up reactions by:
A. Lowering the activation energy ✓ Correct
B. Being consumed in the reaction
C. Changing the equilibrium constant
D. Raising the activation energy
Solution: Enzymes lower the activation energy of a reaction; they are not used up and do not alter the equilibrium.
Q2 — Enzymes · easy · theory
The specific region of an enzyme where the substrate binds is the:
A. Allosteric site only
B. Cofactor
C. Active site ✓ Correct
D. Backbone
Solution: The active site is a crevice/pocket shaped to fit specific substrate(s) forming an enzyme–substrate complex.
Q3 — Enzymes · medium · theory
The non-protein component required by some enzymes for activity is a ______; if it is a tightly bound organic molecule it is a ______:
A. Substrate; product
B. Coenzyme; substrate
C. Cofactor; prosthetic group ✓ Correct
D. Inhibitor; activator
Solution: Cofactors may be prosthetic groups (tightly bound), coenzymes (loosely bound organic, e.g. NAD) or metal ions.
Q4 — Enzymes · medium · theory
Enzyme activity typically shows an optimum with respect to temperature and pH because beyond the optimum the enzyme:
A. Denatures / loses its active conformation ✓ Correct
B. Becomes a substrate
C. Gains a cofactor
D. Increases activity indefinitely
Solution: Enzymes work best at an optimum T and pH; high temperature/extreme pH denatures the protein, abolishing activity.
Q5 — Enzymes · hard · theory
A competitive inhibitor decreases enzyme activity because it:
A. Resembles the substrate and competes for the active site ✓ Correct
B. Denatures the enzyme permanently
C. Binds the allosteric site only
D. Increases substrate concentration
Solution: Competitive inhibitors (e.g. malonate for succinic dehydrogenase) resemble the substrate and can be overcome by more substrate.
Q6 — Enzymes · hard · theory
In the six IUB classes of enzymes, an enzyme catalysing the transfer of a phosphate group between substrates is a:
A. Hydrolase
B. Oxidoreductase
C. Transferase ✓ Correct
D. Lyase
Solution: Transferases move a group (e.g. phosphate) between molecules; oxidoreductases handle redox, hydrolases hydrolyse bonds, lyases add/remove groups forming double bonds.