NEET Biology Breathing and Exchange of Gases MCQs Set 04

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Multiple Choice Questions

Question 1: Which statement is incorrect?
(a) The residual air in lungs slightly decreases the efficiency of respiration in mammals
(b) The presence of non-respiratory air sacs increases the efficiency of respiration in birds
(c) In insects, circulating body fluids serve to distribute oxygen to tissues
(d) The principle of countercurrent flow facilitates efficient respiration in gills of fishes
Show Answer & Explanation

Answer: (c) In insects, circulating body fluids serve to distribute oxygen to tissues

Explanation:
1. In insects oxygen is carried directly to tissues by the tracheal tubes, not by body fluids.

Teacher's Note:
1. Insect blood (haemolymph) has no respiratory pigment.

Question 2: The majority of carbon dioxide produced by body cells is transported to the lungs:
(a) Dissolved in the blood
(b) As bicarbonates
(c) As carbonates
(d) Attached to haemoglobin
Show Answer & Explanation

Answer: (b) As bicarbonates

Explanation:
1. About 70% of CO2 is carried as bicarbonate ions.

Teacher's Note:
1. About 20 to 25% is carried as carbaminohaemoglobin.

Question 3: Bowman's glands are located in the:
(a) Olfactory epithelium of the nose
(b) Proximal end of uriniferous tubules
(c) Anterior pituitary
(d) Female reproductive system of cockroach
Show Answer & Explanation

Answer: (a) Olfactory epithelium of the nose

Explanation:
1. Bowman's glands in the olfactory epithelium secrete mucus that dissolves odorants.

Teacher's Note:
1. Do not confuse with Bowman's capsule of the nephron.

Question 4: Arrange in the order of increasing volume: (A) tidal volume, (B) residual volume, (C) inspiratory reserve volume, (D) vital capacity.
(a) A < B < C < D
(b) A < C < B < D
(c) A < D < C < B
(d) A < D < B < C
Show Answer & Explanation

Answer: (a) A < B < C < D

Explanation:
1. TV is about 500 mL, RV about 1100 to 1200 mL, IRV 2500 to 3000 mL and VC about 4000 mL.

Teacher's Note:
1. Know the standard values.

Question 5: What is the vital capacity of our lungs?
(a) Inspiratory reserve volume plus expiratory reserve volume
(b) Total lung capacity minus residual volume
(c) Inspiratory reserve volume plus tidal volume
(d) Total lung capacity minus expiratory reserve volume
Show Answer & Explanation

Answer: (b) Total lung capacity minus residual volume

Explanation:
1. VC = TLC - RV = IRV + TV + ERV.

Teacher's Note:
1. Another way to write it is TLC minus RV.

Question 6: Respiratory capacities (a) residual volume, (b) vital capacity, (c) inspiratory reserve volume, (d) inspiratory capacity and the jumbled volumes 2500 mL, 3500 mL, 1200 mL, 4500 mL. Which one is the correct matching of two capacities and volumes?
(a) (a) 4500 mL, (b) 3500 mL
(b) (b) 2500 mL, (c) 4500 mL
(c) (c) 1200 mL, (d) 2500 mL
(d) (d) 3500 mL, (a) 1200 mL
Show Answer & Explanation

Answer: (d) (d) 3500 mL, (a) 1200 mL

Explanation:
1. The adult values are RV 1200 mL, VC 4500 mL, IRV 2500 mL and IC 3500 mL, so d-3500 and a-1200 is the correct pair.

Teacher's Note:
1. IC = TV + IRV = 500 + 3000.

Question 7: What is true about RBCs in humans?
(a) They do not carry CO2 at all
(b) They carry about 20 to 25 per cent of CO2
(c) They transport 99.5 per cent of O2
(d) They transport only 80 per cent of oxygen and the rest 20 per cent is in the dissolved state in plasma
Show Answer & Explanation

Answer: (b) They carry about 20 to 25 per cent of CO2

Explanation:
1. RBCs carry about 20 to 25% of CO2 as carbaminohaemoglobin and about 97% of O2.

Teacher's Note:
1. Another 70% of CO2 is carried as bicarbonate.

Question 8: Two friends are eating together on a dining table. One suddenly starts coughing while swallowing some food. This coughing would have been due to improper movement of:
(a) Epiglottis
(b) Diaphragm
(c) Neck
(d) Tongue
Show Answer & Explanation

Answer: (a) Epiglottis

Explanation:
1. If the epiglottis fails to cover the glottis, food enters the larynx and triggers coughing.

Teacher's Note:
1. The epiglottis closes the glottis during swallowing.

Question 9: 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) Raises the pCO2 of blood to 75 mm of Hg
(c) Is enough to keep oxyhaemoglobin saturation at 96%
(d) Helps in releasing more O2 to the epithelial tissues
Show Answer & Explanation

Answer: (a) Acts as a reserve during muscular exercise

Explanation:
1. Venous blood still holds about 75% of its oxygen, which can be supplied during heavy exercise.

Teacher's Note:
1. This is the oxygen reserve of the blood.

Question 10: The bulk of carbon dioxide released from body tissues into the blood is present as:
(a) Carbamino-haemoglobin in RBCs
(b) Bicarbonate in blood plasma and RBCs
(c) Free CO2 in blood plasma
(d) 70% carbamino-haemoglobin and 30% as bicarbonate
Show Answer & Explanation

Answer: (b) Bicarbonate in blood plasma and RBCs

Explanation:
1. About 70% is carried as bicarbonate in plasma and RBCs.

Teacher's Note:
1. Carbonic anhydrase catalyses the formation of carbonic acid.

Question 11: Which is the correct statement for respiration in humans?
(a) Workers in grinding and stone-breaking industries may suffer from lung fibrosis
(b) About 90% of CO2 is carried by haemoglobin as carbamino haemoglobin
(c) Cigarette smoking increases the surface area available for gas exchange
(d) Neural signals from the pneumotaxic centre in the pons region of the brain can increase the duration of inspiration
Show Answer & Explanation

Answer: (a) Workers in grinding and stone-breaking industries may suffer from lung fibrosis

Explanation:
1. Dust of grinding and stone-breaking industries causes inflammation and fibrosis of the lungs. Only 20 to 25% of CO2 is carried as carbaminohaemoglobin, smoking damages the alveoli and the pneumotaxic centre shortens inspiration.

Teacher's Note:
1. Fibrosis or silicosis is an occupational lung disease.

Question 12: During swallowing of food, which structure prevents the entry of food into the glottis?
(a) Semilunar valve
(b) Circular muscular flap
(c) Cartilaginous flap
(d) Circular sphincter
Show Answer & Explanation

Answer: (c) Cartilaginous flap

Explanation:
1. The epiglottis is a cartilaginous flap that covers the glottis.

Teacher's Note:
1. It is made of elastic cartilage.

Question 13: Approximately seventy percent of carbon dioxide absorbed by the blood will be transported to the lungs:
(a) As bicarbonate ions
(b) In the form of dissolved gas molecules
(c) By binding to RBCs
(d) As carbamino-haemoglobin
Show Answer & Explanation

Answer: (a) As bicarbonate ions

Explanation:
1. About 70% is carried as bicarbonate ions.

Teacher's Note:
1. CO2 forms carbonic acid in RBCs and dissociates to H+ and HCO3-.

Question 14: When you hold your breath, which gas change in blood first leads to the urge to breathe?
(a) Rising CO2 concentration
(b) Falling CO2 concentration
(c) Rising CO2 and falling O2 concentration
(d) Falling O2 concentration
Show Answer & Explanation

Answer: (a) Rising CO2 concentration

Explanation:
1. A rise in CO2 and H+ stimulates the chemosensitive area of the medulla first.

Teacher's Note:
1. The O2 effect is secondary.

Question 15: Asthma may be attributed to:
(a) Bacterial infection of the lungs
(b) Allergic reaction of the mast cells in the lungs
(c) Inflammation of the trachea
(d) Accumulation of fluid in the lungs
Show Answer & Explanation

Answer: (b) Allergic reaction of the mast cells in the lungs

Explanation:
1. Asthma is an allergic inflammation and bronchoconstriction involving mast cells.

Teacher's Note:
1. It causes wheezing and difficulty in breathing.

Question 16: The partial pressure of oxygen in the alveoli of the lungs is:
(a) Less than that in the blood
(b) Less than that of carbon dioxide
(c) Equal to that in the blood
(d) More than that in the blood
Show Answer & Explanation

Answer: (d) More than that in the blood

Explanation:
1. Alveolar pO2 is 104 mm Hg, higher than the 40 mm Hg in deoxygenated blood, so oxygen diffuses into the blood.

Teacher's Note:
1. Diffusion is down the gradient.

Question 17: Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because:
(a) There is a positive intrapleural pressure
(b) Pressure in the lungs is higher than atmospheric pressure
(c) There is a negative pressure in the lungs
(d) There is a negative intrapleural pressure pulling at the lung walls
Show Answer & Explanation

Answer: (d) There is a negative intrapleural pressure pulling at the lung walls

Explanation:
1. The intrapleural pressure is always lower than the pressure inside the lungs, which holds the lungs expanded.

Teacher's Note:
1. Loss of this negative pressure causes lung collapse (pneumothorax).

Question 18: The respiratory rhythm centre is regulated by:
(a) Difference between solubility of gases
(b) Chemosensitive area present in medulla oblongata for pCO2 and pH
(c) Diencephalon and brain stem
(d) Chemosensitive area present in the wall of lungs
Show Answer & Explanation

Answer: (b) Chemosensitive area present in medulla oblongata for pCO2 and pH

Explanation:
1. A chemosensitive area adjacent to the rhythm centre in the medulla senses CO2 and H+.

Teacher's Note:
1. The rhythm centre lies in the medulla.

Question 19: Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration because of:
(a) Inspiratory reserve volume
(b) Tidal volume
(c) Expiratory reserve volume
(d) Residual volume
Show Answer & Explanation

Answer: (d) Residual volume

Explanation:
1. The residual volume keeps the alveoli partly inflated.

Teacher's Note:
1. RV cannot be expelled by any effort.

Question 20: CO poisoning causes a decrease in oxygen availability to the tissues because:
(a) It binds haemoglobin to form stable compound carboxyhaemoglobin
(b) It increases CO2 concentration in our body
(c) It is a toxic gas, so main body organs like brain fail
(d) CO impedes CO2 transportation
Show Answer & Explanation

Answer: (a) It binds haemoglobin to form stable compound carboxyhaemoglobin

Explanation:
1. CO forms a stable complex with Hb that cannot carry oxygen.

Teacher's Note:
1. The affinity of CO is about 200 times that of oxygen.

Question 21: Which of the following options correctly represents the lung conditions in asthma and emphysema, respectively?
(a) Inflammation of bronchioles; decreased respiratory surface
(b) Increased number of bronchioles; increased respiratory surface
(c) Increased respiratory surface; inflammation of bronchioles
(d) Decreased respiratory surface; inflammation of bronchioles
Show Answer & Explanation

Answer: (a) Inflammation of bronchioles; decreased respiratory surface

Explanation:
1. Asthma involves inflammation of the bronchi and bronchioles. Emphysema damages alveolar walls and decreases respiratory surface.

Teacher's Note:
1. Match each disease with its site.

Question 22: Match: a. Tidal volume, b. Inspiratory reserve volume, c. Expiratory reserve volume, d. Residual volume with i. 2500-3000 mL, ii. 1100-1200 mL, iii. 500-550 mL, iv. 1000-1100 mL.
(a) a-iii, b-ii, c-i, d-iv
(b) a-iii, b-i, c-iv, d-ii
(c) a-iii, b-iv, c-ii, d-iii
(d) a-iv, b-iii, c-ii, d-i
Show Answer & Explanation

Answer: (b) a-iii, b-i, c-iv, d-ii

Explanation:
1. TV is 500 to 550 mL, IRV 2500 to 3000 mL, ERV 1000 to 1100 mL and RV 1100 to 1200 mL.

Teacher's Note:
1. Learn the four volumes with their ranges.

Question 23: Which of the following is an occupational respiratory disorder?
(a) Anthracis
(b) Silicosis
(c) Botulism
(d) Emphysema
Show Answer & Explanation

Answer: (b) Silicosis

Explanation:
1. Silicosis arises from inhaling silica dust in mining and stone cutting.

Teacher's Note:
1. Asbestosis is another occupational lung disorder.

Question 24: The oxygen dissociation curve represents:
(a) Percent saturation of Hb with oxygen
(b) Partial pressure of oxygen
(c) Partial pressure of carbon dioxide
(d) Percent saturation of Hb with carbon dioxide
Show Answer & Explanation

Answer: (a) Percent saturation of Hb with oxygen

Explanation:
1. The curve plots percent saturation of haemoglobin with O2 against pO2.

Teacher's Note:
1. It is sigmoid in shape.

Question 25: CO2 binds the alpha and beta chains of haemoglobin to form:
(a) Carbaminohaemoglobin
(b) Oxyhaemoglobin
(c) Deoxyhaemoglobin
(d) Carboxyhaemoglobin
Show Answer & Explanation

Answer: (a) Carbaminohaemoglobin

Explanation:
1. CO2 binds the amino groups of globin chains and forms carbaminohaemoglobin.

Teacher's Note:
1. CO forms carboxyhaemoglobin.

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