MCQ Collection
MDCAT 2026 MCQs
Practice MDCAT 2026 questions with answers and explanations.
Choose an option to check your answer.
Correct Answer: B. Individuals vary in heritable traits and reproductive success
Explanation:
Natural selection requires heritable variation and unequal reproduction.
Favorable traits can increase over generations.
Choose an option to check your answer.
Correct Answer: C. Substrate binding causes a conformational adjustment in the active site
Explanation:
The active site is flexible rather than perfectly rigid.
Binding aligns catalytic groups and stabilizes the transition state.
Choose an option to check your answer.
Correct Answer: C. Individuals vary in heritable traits and reproductive success
Explanation:
Natural selection requires heritable variation and unequal reproduction.
Favorable traits can increase over generations.
Choose an option to check your answer.
Correct Answer: D. Substrate binding causes a conformational adjustment in the active site
Explanation:
The active site is flexible rather than perfectly rigid.
Binding aligns catalytic groups and stabilizes the transition state.
Choose an option to check your answer.
Correct Answer: D. Individuals vary in heritable traits and reproductive success
Explanation:
Natural selection requires heritable variation and unequal reproduction.
Favorable traits can increase over generations.
Choose an option to check your answer.
Correct Answer: A. Receptor → sensory neuron → relay neuron → motor neuron → effector
Explanation:
A reflex begins with receptor stimulation and sensory input.
Motor output then activates an effector.
Choose an option to check your answer.
Correct Answer: A. Substrate binding causes a conformational adjustment in the active site
Explanation:
The active site is flexible rather than perfectly rigid.
Binding aligns catalytic groups and stabilizes the transition state.
Choose an option to check your answer.
Correct Answer: B. Receptor → sensory neuron → relay neuron → motor neuron → effector
Explanation:
A reflex begins with receptor stimulation and sensory input.
Motor output then activates an effector.
Choose an option to check your answer.
Correct Answer: B. Most active sites become occupied
Explanation:
Once active sites are saturated, added substrate cannot greatly increase rate.
Enzyme concentration becomes limiting.
Choose an option to check your answer.
Correct Answer: C. Cerebellum
Explanation:
The cerebellum integrates sensory information for posture and coordination.
Damage commonly causes unsteady movement.
Choose an option to check your answer.
Correct Answer: C. Most active sites become occupied
Explanation:
Once active sites are saturated, added substrate cannot greatly increase rate.
Enzyme concentration becomes limiting.
Choose an option to check your answer.
Correct Answer: D. Cerebellum
Explanation:
The cerebellum integrates sensory information for posture and coordination.
Damage commonly causes unsteady movement.
