MCQ Collection
MDCAT Biology MCQs
Practice MDCAT Biology questions with answers and explanations.
Choose an option to check your answer.
Correct Answer: C. Simpler inorganic substances under early-Earth conditions
Explanation:
Chemical evolution describes prebiotic formation of organic compounds.
These compounds preceded the first cellular life.
Choose an option to check your answer.
Correct Answer: D. Leydig cells
Explanation:
Luteinizing hormone stimulates Leydig cells.
Testosterone supports male reproductive function and secondary characteristics.
Choose an option to check your answer.
Correct Answer: A. Leydig cells
Explanation:
Luteinizing hormone stimulates Leydig cells.
Testosterone supports male reproductive function and secondary characteristics.
Choose an option to check your answer.
Correct Answer: B. Leydig cells
Explanation:
Luteinizing hormone stimulates Leydig cells.
Testosterone supports male reproductive function and secondary characteristics.
Choose an option to check your answer.
Correct Answer: C. Support and nourish developing sperm
Explanation:
Sertoli cells form the environment for spermatogenesis.
They also respond to follicle-stimulating hormone.
Choose an option to check your answer.
Correct Answer: D. Support and nourish developing sperm
Explanation:
Sertoli cells form the environment for spermatogenesis.
They also respond to follicle-stimulating hormone.
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.
