NCERT Class 11 Chapter 17 Biology Breathing and Exchange of Gases MCQ

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1. Bulk of carbon dioxide (CO₂) released from body tissues into the blood is present as

A. bicarbonate in blood plasma and RBCs

B. 70% carbamino- haemoglobin and 30% as bicarbonate

C. carbamino-hemoglobin in RBCs

D. free CO₂ in blood plasma

2. A large proportion of oxygen is left unused in the human blood even after its uptake by the body tissues. This O₂

A. acts as a reserve during muscular exercise

B. is enough to keep oxyhemoglobin saturation at 96%

C. helps in releasing more O₂ to the epithelial tissues

D. None of these

3. Oxygen dissociation curve of haemoglobin is

A. Sigmoid

B. Hyperbolic

C. Hypobolic

D. Linear

4. Which one of the following organs in the human body is most affected due to shortage of oxygen?

A. Brain

B. Kidney

C. Skin

D. Intestine

5. When CO₂ concentration in blood increases, breathing becomes

A. faster and deeper

B. slow and deep

C. there is no effect on breathing

D. shallower and slow

6. The largest quantity of air that can be expired after a maximal inspiratory effort is called

A. vital capacity

B. residual volume

C. tidal volume

D. total lung volume

7. Which one of the following statements is incorrect ?

A. In insects, circulating body fluids serve to distribute oxygen to tissues

B. The principle of counter current flow facilitates efficient respiration in gills of fishes

C. The residual air in lungs slightly decreases the efficiency of respriration in mammals.

D. None of these

8. Emphysema developes mainly because of

A. Spasm of the smooth muscles of bronchioles

B. Cigarette smoking

C. Inflammation of the alveoli

D. Allergy or hypersensitisation

9. During inspiration the diaphragm

A. contracts and flattens

B. relaxes to become dome-shaped

C. shows no change

D. None of these

10. The volume of air breathed in and out during normal breathing is called

A. Tidal volume

B. Expiratory reserve volume

C. Vital capacity

D. None of these

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

A. Oxygen carrying capacity of hemoglobin decreases

B. RBCs count increases

C. RBCs count decreases

D. Oxygen carying capacity of haemoglobin increases

12. Even when there is no air in it, human trachea does not collapse due to presence of

A. Cartilaginous rings

B. Turgid pressure

C. Bony rings

D. Chitinous rings

13. The structure which does not contribute to the breathing movements in mammals is

A. Larynx

B. Diaphragm

C. Ribs

D. Intercostal muscles

14. In emphysema

A. Gas exchange area of lungs is reduced

B. Gas exchange area of lungs is increased

C. Trachea gets narrowed

D. Larynx is permanently closed

15. Which of the following changes occur in diaphragm and intercostal muscles when expiration of air takes place?

A. External intercostal muscles and diaphargm relax

B. External intercostal muscles and diaphargm contract

C. External intercostal muscles contract and diaphargm relaxes

D. External intercostal muscles relax and diaphargm contracts

16. When you exhale, the diaphragm

A. relaxes and arches

B. relaxes and flattens

C. contracts and arches

D. contracts and flattens

17. Smoking destroys the cilia in the respiratory passageways. This

A. makes it harder to keep the lungs clean

B. slows blood flow through lung blood vessels

C. decreases the surface area for respiration.

D. makes it harder to move air in and out of the lungs

18. Gas flows into the lungs of mammals during inspiration because

A. The pressure in the lungs falls below atmospheric pressure

B. The pressure in the lungs rises above atmospheric pressure

C. The volume of the lungs decreases

D. The diaphragm moves upward toward the lungs

19. The function of the mucus elevator in the mammalian respiratory system is to

A. trap and remove particulate matter that has entered the respiratory system.

B. stimulate contraction of rib musculature during forcible exhalation

C. produce negative pressure during inhalation

D. move surfactant from the bronchi to the alveoli

20. During inspiration, the air is brought into the lungs by the working of the thoracoabdominal pump whereby the

A. all of the above

B. abdominal muscles relax

C. chest muscles pull the ribs up and out to widen the thoracic cavity

D. diaphragm contracts to lengthen the thoracic cavity

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21. The alveolar epithelium in the lung is

A. non-ciliated columnar

B. non-ciliated squamous

C. ciliated columnar

D. ciliated squamous

22. Skin is an accessory organ of respiration in

A. human

B. frog

C. rabbit

D. lizard

23. Carbon dioxide is transported from tissues to respiratory surface by only

A. plasma and erythrocytes

B. plasma

C. erythrocytes

D. erythrocytes and leucocytes

24. Air is breathed through

A. trachea—lungs—larynx—pharynx—alveoli

B. nose—larynx—pharynx—bronchus—alveoli—bronchioles

C. nostrils—pharynx—larynx—trachea—bronchi—bronchioles—alveoli

D. nose — mouth — lungs

25. Although much CO₂ is carried in blood, yet blood does not become acidic, because

A. it is absorbed by the leucocytes

B. blood buffers play an important role in CO₂ transport

C. it combines with water to form H₂CO₃ which is neutralized by Na₂CO₃

D. it is continuously diffused through tissues and is not allowed to accumulate