Free practice › Class 11 › Biology › Chapter 14
Breathing and Exchange of Gases — NEET MCQs with answers
Chapter 14 describes the human respiratory system — the conducting part and the alveoli — the mechanics of breathing, the exchange of O2 and CO2 by diffusion at the alveoli and tissues, their transport in blood (O2 as oxyhaemoglobin; CO2 mainly as bicarbonate), the neural regulation of respiration, and disorders of the respiratory system.
Topics in this chapter
- 14.1 Respiratory Organs
- 14.2 Mechanism of Breathing
- 14.3 Exchange of Gases
- 14.4 Transport of Gases
- 14.5 Regulation of Respiration
- 14.6 Disorders of the Respiratory System
Free practice questions
During breath-holding, the rising CO2 in blood eventually forces breathing to resume. This is best explained by:
- A. Direct stimulation of the diaphragm by CO2
- B. Activation of the chemosensitive area which signals the rhythm centre
- C. Hormonal control of the medulla
- D. Stimulation of the pneumotaxic centre by falling O2
Show answer
Answer: B — Rising CO2 and H+ activate the chemosensitive area, which signals the medullary rhythm centre to adjust respiration so that these substances are eliminated. Falling O2 is described by NCERT as an insignificant regulator.
NCERT Class 11 Biology Ch 14.5
A man's vital capacity is 4400 mL and his total lung capacity is 5500 mL. What percentage of his total lung capacity can be exchanged voluntarily?
- A. 100%
- B. 75%
- C. 60%
- D. 80%
Show answer
Answer: D — Only the vital capacity can be moved voluntarily. (4400 / 5500) x 100 = 80%. The remaining 20% is the residual volume, which cannot be expelled.
NCERT Class 11 Biology Ch 14.2
The thoracic chamber is formed dorsally by the:
- A. Ribs
- B. Sternum
- C. Vertebral column
- D. Diaphragm
Show answer
Answer: C — The thoracic chamber is formed dorsally by the vertebral column.
NCERT Class 11 Biology Ch 14.1
The total thickness of the diffusion membrane being much less than a millimetre is favourable because it:
- A. Keeps the diffusion path short and so the rate of diffusion high
- B. Increases the partial pressure of O2 in the alveoli
- C. Raises the solubility of CO2 in the blood
- D. Allows active transport of gases to occur
Show answer
Answer: A — A very thin barrier means a short diffusion path; membrane thickness is one of the factors affecting the rate of diffusion.
NCERT Class 11 Biology Ch 14.3
As blood reaches the pulmonary (alveolar) capillaries, in which direction does the carbonic anhydrase catalysed reaction proceed?
- A. Towards the formation of HCO₃⁻ and H⁺
- B. The reaction stops completely at the alveoli
- C. Towards the formation of CO₂ and H₂O
- D. Towards the formation of carbamino-haemoglobin
Show answer
Answer: C — At the alveolar site pCO₂ is low, so the reaction runs in the opposite direction — HCO₃⁻ and H⁺ combine to give H₂CO₃ and then CO₂ + H₂O, and the CO₂ is released out.
NCERT Class 11 Biology Ch 14.4
Inflammation is a feature common to which two conditions in section 14.6?
- A. Asthma and emphysema
- B. Asthma and occupational respiratory disorders
- C. Emphysema and occupational respiratory disorders
- D. Only asthma shows inflammation
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Answer: B — Asthma is due to inflammation of bronchi and bronchioles; in occupational disorders, long dust exposure gives rise to inflammation leading to fibrosis.
NCERT Class 11 Biology Ch 14.6
The chemosensitive area is situated adjacent to which centre?
- A. Vasomotor centre
- B. Pneumotaxic centre
- C. Respiratory rhythm centre
- D. Cardiac centre
Show answer
Answer: C — NCERT states that a chemosensitive area is situated adjacent to the rhythm centre, and that it is highly sensitive to CO2 and hydrogen ions.
NCERT Class 11 Biology Ch 14.5
Which of the following pairs of respiratory volumes, when added together, does NOT give any of the pulmonary capacities defined by NCERT?
- A. ERV + RV
- B. IRV + RV
- C. TV + ERV
- D. TV + IRV
Show answer
Answer: B — IC = TV + IRV, EC = TV + ERV and FRC = ERV + RV are all NCERT-defined capacities. IRV + RV is not a defined pulmonary capacity.
NCERT Class 11 Biology Ch 14.2
The fourth step of respiration is:
- A. Utilisation of O2 by the cells
- B. Diffusion of O2 and CO2 between blood and tissues
- C. Pulmonary ventilation
- D. Transport of gases by the blood
Show answer
Answer: B — Step (iv) is diffusion of O2 and CO2 between blood and tissues.
NCERT Class 11 Biology Ch 14.1
Partial pressures of respiratory gases in NCERT Table 14.1 are expressed in:
- A. atm
- B. kPa
- C. mm Hg
- D. cm H2O
Show answer
Answer: C — All partial-pressure values in Table 14.1 are given in mm Hg.
NCERT Class 11 Biology Ch 14.3
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