NEET (UG)

Practice Test 1 — Breathing and Exchange of Gases

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct)

Question 1

The site of gas exchange in the human lung is the:

Solution: Alveoli are the gas-exchange surface.

Question 2

During inspiration the volume of the thoracic cavity:

Solution: Thoracic volume increases, lowering intrapulmonary pressure.

Question 3

Vital capacity is:

Solution: VC = TV + IRV + ERV.

Question 4

The air left in the lungs after the most forceful expiration is the:

Solution: Residual volume always remains in the lungs.

Question 5

About 97% of oxygen is carried in the blood:

Solution: Most O₂ is bound to haemoglobin.

Question 6

Most CO₂ is transported as:

Solution: ~70% of CO₂ travels as bicarbonate.

Question 7

The respiratory rhythm centre is in the:

Solution: The rhythm centre is in the medulla oblongata.

Question 8

Damage to alveolar walls, mainly due to smoking, characterises:

Solution: Emphysema = alveolar damage, mainly from smoking.

Section B — Assertion & Reason

Question 9

A: During inspiration air moves into the lungs.
R: Contraction of the diaphragm and external intercostals raises the thoracic volume and lowers the intrapulmonary pressure below atmospheric.

Solution: The pressure dropping below atmospheric is exactly what draws air in — R explains A.

Question 10

A: In actively respiring tissues, haemoglobin releases oxygen more easily.
R: High CO₂, low pH and high temperature shift the oxygen dissociation curve to the right (Bohr effect).

Solution: The right shift (Bohr effect) lowers Hb's O₂ affinity, releasing O₂ — R explains A.

Question 11

A: Oxygen is the main chemical that regulates the rate of breathing.
R: A chemosensitive area in the brain is highly sensitive to CO₂ and H⁺ ions.

Solution: A is false — CO₂/H⁺ (not O₂) are the main regulators; R correctly states the chemosensitive area responds to CO₂ and H⁺.

Question 12

A: Residual volume is not included in the vital capacity.
R: Residual volume is the air that can never be exhaled, even after a forced expiration.

Solution: Since RV can't be exhaled, it cannot be part of the maximum exhaled volume (VC) — R explains A.