Top 25+ Breathing and Exchange of Gases - Biology Questions and Answers For NEET 2024 Exam Preparation

Q1. In man and mammals, air passes from outside into the lungs through

1. nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli
2. nasal cavity → pharynx → larynx → trachea → bronchioles → bronchi → alveoli
3. nasal cavity → larynx → pharynx → trachea → bronchi → alveoli
4. nasal cavity → larynx → pharynx → trachea → bronchioles → alveoli

Answer: (a)

Air travels through nose and mouth. The respiratory system moves air in and out of the body by using oxygen and eliminating carbon dioxide (a gas produced when cells use oxygen).

The respiratory system includes the nose, mouth, trachea, bronchi, diaphragm and lungs. The complete passage through which air passes from outside into the lungs are: nasal cavity – pharynx – larynx – trachea – bronchi – bronchioles – alveoli.

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Q2. As blood becomes fully $O_{2}$ saturated, haemoglobin combines with____ molecule(s) of oxygen.

1. 2
2. 1
3. 4
4. 8

Answer: (c)

Haemoglobin has 4 subunits, each of which binds to 1 molecule of $O_{2}$ for a total of 4 molecules of $O_{2}$ bound to 1 haemoglobin molecule.

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Q3. In emphysema –

1. Gas exchange area of lungs is increased
2. Trachea gets narrowed
3. Gas exchange area of lungs is reduced
4. Larynx is permanently closed

Answer: (c)

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Q4. The chloride shift in red blood cells is the movement of

1. chloride ions from the blood into the glomerular filtrate for excretion.
2. cations into the cell to balance its uptake of chloride ions.
3. chloride ions out of the cell to balance the release of hydrogen carbonate ions.
4. chloride ions into the cell to balance its uptake of hydrogen carbonate ions.

Answer: (c)

Most of the hydrogen carbonate ions formed in the red blood cells diffuse out of the plasma along a concentration gradient and combine with sodium in the plasma to form sodium hydrogen carbonate.

The loss of negatively-charged hydrogen carbonate ions leaves them with a more positive charge that is balanced by chloride ions diffusing into the red blood cells from the plasma.

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Q5. The blood leaving the lungs has all its haemoglobin oxygenated and gives up oxygen to the tissues, because

1. $O_{2}$-concentration in tissues is higher and $CO_{2}$concentration lower as compared to lungs
2. oxyhaemoglobin undergoes reduction
3. the tissues can absorb $O_{2}$ from oxyhaemoglobin
4. $O_{2}$-concentration in tissues is lower and $CO_{2}$concentration higher than in lungs.

Answer: (d)

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Q6. Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration, because of:

1. Tidal Volume
2. Expiratory Reserve Volume
3. Inspiratory Reserve Volume
4. Residual Volume

Answer: (d)

Volume of air present in lungs after forceful expiration as residual volume prevents the collapsing of alveoli.

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Q7. Assertion: Blood of insects is colourless.

Reason: The blood of insect does not play any role in transport of oxygen.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (c)

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Q8. Name the pulmonary disease in which alveolar surface area involved in gas exchange is drastically reduced due to damage in the alveolar walls :

1. Pleurisy
2. Emphysema
3. Asthma
4. Pneumonia

Answer: (b)

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Q9. Sites of gaseous exchange in lungs are

1. Bronchi
2. Alveoli
3. Bronchioles
4. Pleura

Answer: (b)

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Q10. What is the vital capacity of our lungs?

1. Total lung capacity minus expiratory reserve volume
2. Inspiratory reserve volume plus expiratory reserve volume
3. Inspiratory reserve volume plus tidal volume
4. Total lung capacity minus residual volume

Answer: (d)

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Q11. The relative proportion between the volume of $CO_{2}$ released and $O_{2}$ absorbed in respiration is termed as

1. Respiratory quotient
2. Respiratory phase
3. Respiratory exchange
4. None of the above

Answer: (a)

Respiratory quotient is the ratio of carbon dioxide released to oxygen usage during respiration.

R. Q. = ${\text"Volume of CO_{2} formed"}/{\text"Volume of O_{2} Outilized"}$

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Q12. Assertion: In mammals, complex respiratory system has developed.

Reason: Mammalian skin is impermeable to gases.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (a)

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Q13. What would happen if human blood becomes acidic (low pH)?

1. Oxygen carrying capacity of haemoglobin decreases.
2. Oxygen carrying capacity of haemoglobin increases.
3. RBCs count increases.
4. RBCs count decreases.

Answer: (a)

If human blood becomes acidic, oxygen carrying capacity of haemoglobin decreases.

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Q14. It is know that exposure to carbon monoxide is harmful to animals because

1. it reduces $O_{2}$ transport
2. it increases C$O_{2}$ transport
3. it reduces C$O_{2}$ transport
4. it increases $O_{2}$ transport

Answer: (a)

Haemoglobin consists of a protein globin and pigment heme. The four portions of iron in heme combine with molecule of oxygen. It is an easy reversible reaction to form oxy haemoglobin

$Hb + O_{2} ⇋ Hbo_{2}$

Whereas, the complex formed by the reaction of carbon mono oxide and haemoglobin is incredibly strong(Haemoglobin) (Carboxy haemoglobin)

${Hb + CO} ↙ {\text"(Haemoglobin)"} ⇋ {HbCO} ↙ {\text"Carboxy haemoglobin"}$

As a result of this strong between the haemoglobin and carbon mono oxide the haemoglobin looses its affinity to oxygen thus may lead to choking or even death.

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Q15. Regarding the functions of our respiratory system, mark the wrong entry.

1. Warms up the air
2. Humidifies the air
3. Diffusion of gases
4. Cleans up the air

Answer: (d)

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Q16. Approximately seventy percent of carbon dioxide absorbed by the blood will be transported to the lungs

1. In the form of dissolved gas molecules
2. By binding to R.B.C.
3. As bicarbonate ions
4. As carbamino-haemoglobin

Answer: (c)

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Q17. Emphysema develops mainly because of

1. Spasm of the smooth muscles of bronchioles
2. Cigarette smoking
3. Allergy or hyper sensitisation
4. Inflammation of the alveoli

Answer: (b)

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Q18. 6000 to 8000 ml of air is the

1. Volume of normal expiration per minute
2. Sum of IRV + ERV
3. Vital capacity of lungs
4. Inspiratory capacity of lungs

Answer: (a)

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Q19. Name the chronic respiratory disorder caused mainly by cigarette smoking.

1. Respiratory alkalosis
2. Respiratory acidosis
3. Emphysema
4. Asthma

Answer: (c)

Emphysema is a chronic obstructive pulmonary disease (COPD) caused due to cigarette smoking. It is an inflation or abnormal distention of the bronchioles or alveolar sacs of the lungs which causes irreversible distension and loss of elasticity of alveoli of the lungs.

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Q20. EC (expiratory capacity) is equal to

1. IRV+ TV
2. ERV + TV
3. VC + RV
4. ERV + TV + IRV

Answer: (b)

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Q21. Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?

1. The lungs can be made fully empty by forcefully breathing out all air from them.
2. One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.
3. One can breathe out air totally without oxygen.
4. One can breathe out air through Eustachian tubes by closing both the nose and the mouth.

Answer: (b)

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Q22. Assertion: The maximum amount of $CO_2$ is converted into bicarbonate ion in RBCs.

Reason: RBCs contain a very high concentration of the enzyme, carbonic anhydrase.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (b)

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Q23. Reduction in pH of blood will

1. release bicarbonate ions by the liver
2. decrease the affinity of haemoglobin with oxygen
3. reduce the rate of heartbeat
4. reduce the blood supply to the brain

Answer: (b)

Reduction in pH of blood causes oxygen haemoglobin dissociation curve to shift to the right which indicates dissociation of oxygen from haemoglobin. This decreases affinity of haemoglobin for oxygen.

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Q24. When you exhale, the diaphragm

1. relaxes and flattens.
2. contracts and arches.
3. relaxes and arches.
4. contracts and flattens.

Answer: (c)

This decreases the size of the thoracic cavity, which increases the pressure within the thoracic cavity, forcing air out of the lungs.

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Q25. The figure shows a diagrammatic view of human respiratory system with labels A, B, C and D. Select the option which gives correct identification and main function and / or characteristic.

1. D - Lower end of lungs - Diaphragm pulls it down during inspiration.
2. C - Alveoli - Thin walled vascular bag like structures for exchange of gases.
3. A - Trachea - Long tube supported by complete cartilaginous rings for conducting inspired air.
4. B - Pleural membrane - Surround ribs on both sides to provide cushion against rubbing

Answer: (b)

In the given figure A is trachea. It is supported by incomplete cartilaginous rings which prevent its collapse during inspiration. B is pleural membrane. It encloses lungs. C are alveoli. They are thin walled sacs having extensive network of capillaries for gaseous exchange. D is diaphragm.

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