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Breathing and Exchange of Gases MCQs for NEET — Zoology Questions with Answers

Practice free Breathing and Exchange of Gases (Zoology) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.

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Which set of organs is responsible for respiration in amphibians through 'cutaneous respiration'?

A. Buccal cavity and lungs B. Gills and lungs C. Moist skin only D. Moist skin, buccal cavity, and lungs (at different times/conditions)

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Explanation

The NCERT states, 'Amphibians like frogs can respire through their moist skin (cutaneous respiration) also.' Additionally, for frogs, 'On land, the buccal cavity, skin and lungs act as the respiratory organs.' This implies a dynamic use of different organs depending on the environment.

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The conducting part of the human respiratory system consists of structures from the external nostrils up to what point?

A. Alveoli B. Respiratory bronchioles C. Terminal bronchioles D. Alveolar ducts

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Explanation

According to the NCERT text, 'The part starting with the external nostrils up to the terminal bronchioles constitute the conducting part...'

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Which of the following is NOT a function of the conducting part of the respiratory system?

A. Transporting atmospheric air to the alveoli B. Clearing foreign particles from the air C. Bringing the air to body temperature D. Diffusion of O2 and CO2 between blood and atmospheric air

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Explanation

The NCERT states, 'The conducting part transports the atmospheric air to the alveoli, clears it from foreign particles, humidifies and also brings the air to body temperature.' The 'Exchange part is the site of actual diffusion of O2 and CO2 between blood and atmospheric air.'

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The thoracic chamber is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs, and on the lower side by which structure?

A. Pleural membrane B. Lungs C. Diaphragm D. Trachea

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Explanation

The NCERT text mentions, 'The thoracic chamber is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs and on the lower side by the dome-shaped diaphragm.'

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Inspiration occurs when the intra-pulmonary pressure becomes:

A. Equal to atmospheric pressure B. Greater than atmospheric pressure C. Less than atmospheric pressure D. Zero, relative to atmospheric pressure

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Explanation

The NCERT states, 'Inspiration can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure.'

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What is the approximate volume of air remaining in the lungs even after a forcible expiration?

A. 500 mL B. 1100 mL to 1200 mL C. 2500 mL to 3000 mL D. 5000 mL to 6000 mL

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Explanation

The NCERT defines Residual Volume (RV) as 'Volume of air remaining in the lungs even after a forcible expiration. This averages 1100 mL to 1200 mL.'

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Inspiratory Capacity (IC) is the total volume of air a person can inspire after a normal expiration. It includes:

A. Tidal Volume (TV) + Expiratory Reserve Volume (ERV) B. Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) C. Tidal Volume (TV) + Residual Volume (RV) D. Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV)

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Explanation

As per the NCERT, 'Inspiratory Capacity (IC): Total volume of air a person can inspire after a normal expiration. This includes tidal volume and inspiratory reserve volume (TV+IRV).'

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Which of the following factors is LEAST important for the rate of diffusion of O2 and CO2 across the alveolar membrane?

A. Partial pressure gradient B. Solubility of the gases C. Thickness of the membranes D. Volume of blood flowing through capillaries

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Explanation

The NCERT states, 'O2 and CO2 are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient. Solubility of the gases as well as the thickness of the membranes involved in diffusion are also some important factors that can affect the rate of diffusion.' While blood volume is crucial for transport, the question asks about factors affecting the rate of diffusion across the membrane itself.

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What is the main reason for the much higher diffusion rate of CO2 compared to O2 across the diffusion membrane per unit difference in partial pressure?

A. CO2 has a smaller molecular size. B. CO2 is 20-25 times more soluble than O2. C. The partial pressure gradient for CO2 is always higher. D. O2 molecules are less mobile in the aqueous environment.

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Explanation

The NCERT clearly states, 'As the solubility of CO2 is 20-25 times higher than that of O2, the amount of CO2 that can diffuse through the diffusion membrane per unit difference in partial pressure is much higher compared to that of O2.'

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The diffusion membrane across which O2 and CO2 exchange occurs is made up of which three major layers?

A. Squamous epithelium of bronchioles, endothelium of arteries, and basement substance. B. Cuboidal epithelium of alveoli, endothelium of venules, and connective tissue. C. Thin squamous epithelium of alveoli, endothelium of alveolar capillaries, and basement substance. D. Columnar epithelium of trachea, endothelium of systemic capillaries, and muscular layer.

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Explanation

The NCERT states, 'The diffusion membrane is made up of three major layers namely, the thin squamous epithelium of alveoli, the endothelium of alveolar capillaries and the basement substance...'

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