MDCAT Biology MCQs with Answers – All 16 Units – Page 3

Question 41 Reproduction

What is the role of the acrosome during fertilisation?

Correct answer A. Releasing enzymes that digest a path through the layers around the oocyte

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Question 42 Reproduction

What prevents more than one sperm from fertilising a human oocyte?

Correct answer C. The cortical reaction that hardens the zona pellucida

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Question 43 Reproduction

How many functional gametes are produced from one primary oocyte and from one primary spermatocyte respectively?

Correct answer B. 1 and 4

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Question 44 Reproduction

At what stage is the human female gamete when it is released at ovulation?

Correct answer C. Secondary oocyte arrested in metaphase II

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Question 45 Reproduction

Which organism causes syphilis?

Correct answer A. Treponema pallidum

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Question 46 Reproduction

A man has a burning sensation on urination with a pus-like discharge from the urethra. Which sexually transmitted infection is most likely?

Correct answer A. Gonorrhoea

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Question 47 Reproduction

Which sexually transmitted disease is caused by a virus and produces recurrent painful blisters in the genital area?

Correct answer B. Genital herpes

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Question 48 Reproduction

Which hormone from the hypothalamus stimulates the anterior pituitary to release FSH and LH?

Correct answer A. Gonadotrophin-releasing hormone (GnRH)

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Question 49 Reproduction

Which statement about progesterone is correct?

Correct answer A. It maintains the endometrium and inhibits FSH and LH secretion

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Question 50 Reproduction

Which hormone produced by Sertoli cells exerts negative feedback on FSH secretion?

Correct answer B. Inhibin

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Question 51 Coordination and Control

Why are sensory receptors described as transducers?

Correct answer B. They convert the energy of a stimulus into electrical nerve impulses

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Question 52 Coordination and Control

Which receptors in the retina convert light energy into nerve impulses?

Correct answer D. Rods and cones

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Question 53 Coordination and Control

Which cells form the myelin sheath around axons in the peripheral nervous system?

Correct answer A. Schwann cells

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Question 54 Coordination and Control

Why do impulses travel faster along myelinated axons than along non-myelinated axons of the same diameter?

Correct answer B. Depolarisation jumps from one node of Ranvier to the next

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Question 55 Coordination and Control

In which direction do dendrites normally carry nerve impulses?

Correct answer A. Towards the cell body

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Question 56 Coordination and Control

Which best defines a nerve impulse?

Correct answer B. A wave of depolarisation (action potential) travelling along a neuron

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Question 57 Coordination and Control

What causes the rapid depolarisation phase of an action potential?

Correct answer C. Opening of voltage-gated Na⁺ channels and inflow of Na⁺

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Question 58 Coordination and Control

Which event mainly brings about repolarisation of a neuron after an action potential?

Correct answer B. Outflow of K⁺ through voltage-gated potassium channels

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Question 59 Coordination and Control

What is one important consequence of the refractory period of a neuron?

Correct answer D. Impulses travel in one direction only along the axon

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Question 60 Coordination and Control

What triggers the release of neurotransmitter from a presynaptic knob?

Correct answer C. Entry of Ca²⁺ ions when the action potential arrives

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