NEET Biology Breathing and Exchange of Gases MCQs Set 03

Multiple Choice Questions (MCQs) for NEET Biology: Breathing and Exchange of Gases

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Multiple Choice Questions

Question 1: Which of the following volumes is NOT included in the vital capacity?
(a) ERV
(b) TV
(c) IRV
(d) RV
Show Answer & Explanation

Answer: (d) RV

Explanation:
1. Vital capacity = ERV + TV + IRV, but residual volume remains in the lungs.

Teacher's Note:
1. RV is excluded.

Question 2: The process of gas exchange in the lungs is done by:
(a) Simple diffusion
(b) Active transport
(c) Passive transport
(d) Facilitated diffusion
Show Answer & Explanation

Answer: (a) Simple diffusion

Explanation:
1. O2 and CO2 diffuse down their partial-pressure gradients across the thin respiratory membrane.

Teacher's Note:
1. Gas exchange is by simple diffusion.

Question 3: Which of the following statements is NOT true?
(a) The partial pressure of O2 in deoxygenated blood is 40 mm Hg
(b) The partial pressure of O2 in oxygenated blood is 95 mm Hg
(c) The partial pressure of O2 in alveolar air is 104 mm Hg
(d) The partial pressure of CO2 in alveolar air is 45 mm Hg
Show Answer & Explanation

Answer: (d) The partial pressure of CO2 in alveolar air is 45 mm Hg

Explanation:
1. Alveolar air has a pCO2 of about 40 mm Hg. The value of 45 mm Hg is that of deoxygenated blood.

Teacher's Note:
1. Remember the values 104 and 40 for alveolar air, 40 and 45 for deoxygenated blood.

Question 4: The partial pressure of oxygen in the alveoli, in atmospheric air and in the tissues respectively is (mm Hg):
(a) 40, 159, 45
(b) 40, 0.3, 45
(c) 104, 159, 40
(d) 104, 0.3, 45
Show Answer & Explanation

Answer: (c) 104, 159, 40

Explanation:
1. Alveolar pO2 is 104, atmospheric pO2 is 159 and tissue pO2 is 40 mm Hg.

Teacher's Note:
1. Oxygen moves down this gradient from air to alveoli to blood to tissues.

Question 5: How do the pO2 and pCO2 of atmospheric air compare with those of the alveolar air?
(a) pO2 lesser, pCO2 higher
(b) pO2 higher, pCO2 lesser
(c) pO2 higher, pCO2 higher
(d) pO2 lesser, pCO2 lesser
Show Answer & Explanation

Answer: (b) pO2 higher, pCO2 lesser

Explanation:
1. Atmospheric pO2 is 159 mm Hg against 104 in alveoli, while atmospheric pCO2 is 0.3 against 40 in alveoli.

Teacher's Note:
1. Alveolar air is mixed with residual air and CO2.

Question 6: The partial pressure of CO2 is higher:
(a) At the alveolar level
(b) At the tissue level
(c) In the atmosphere
(d) In oxygenated blood
Show Answer & Explanation

Answer: (b) At the tissue level

Explanation:
1. Tissues produce CO2 and have a pCO2 of about 45 mm Hg, the highest of the options.

Teacher's Note:
1. CO2 diffuses from tissues to blood and then to alveoli.

Question 7: Under normal conditions, 100 mL of blood delivers about ______ to the tissues.
(a) 4 mL O2
(b) 10 mL O2
(c) 5 mL O2
(d) 25 mL O2
Show Answer & Explanation

Answer: (c) 5 mL O2

Explanation:
1. Each 100 mL of oxygenated blood supplies about 5 mL of O2 to the tissues.

Teacher's Note:
1. Blood still has about 15 mL O2 per 100 mL after leaving the tissues.

Question 8: The Haldane effect is due to:
(a) CO2
(b) Lactic acid
(c) pH
(d) Oxyhaemoglobin
Show Answer & Explanation

Answer: (d) Oxyhaemoglobin

Explanation:
1. The Haldane effect: oxygenated haemoglobin binds less CO2, so oxygenation in lungs helps release CO2.

Teacher's Note:
1. Do not confuse it with Bohr effect.

Question 9: What percentage of CO2 is carried in the form of bicarbonate?
(a) 7%
(b) 23%
(c) 50%
(d) 70%
Show Answer & Explanation

Answer: (d) 70%

Explanation:
1. About 70% is carried as bicarbonate, 20 to 25% as carbaminohaemoglobin and 7% dissolved in plasma.

Teacher's Note:
1. Carbonic anhydrase speeds up bicarbonate formation.

Question 10: The effect of CO2 concentration on the dissociation of oxyhaemoglobin is called:
(a) Bohr's effect
(b) Haldane effect
(c) Hamburger effect
(d) Root effect
Show Answer & Explanation

Answer: (a) Bohr's effect

Explanation:
1. Bohr effect: a rise in pCO2 or H+ lowers Hb affinity for O2.

Teacher's Note:
1. It helps release O2 in the tissues.

Question 11: The chloride shift occurs for the transport of:
(a) O2
(b) CO2
(c) CO
(d) O3
Show Answer & Explanation

Answer: (b) CO2

Explanation:
1. Cl- moves into the RBC as HCO3- moves out, helping CO2 transport.

Teacher's Note:
1. It is also called the Hamburger phenomenon.

Question 12: The ratio of oxyhaemoglobin to haemoglobin in blood depends upon:
(a) Oxygen tension
(b) Carbon dioxide tension
(c) Carbonate tension
(d) Bicarbonate tension
Show Answer & Explanation

Answer: (a) Oxygen tension

Explanation:
1. The percentage saturation of Hb depends mainly on the partial pressure (tension) of oxygen.

Teacher's Note:
1. The relation is given by the oxygen dissociation curve.

Question 13: The exchange of bicarbonate and chloride ions between RBC and plasma is called:
(a) Chloride shift
(b) Bohr's effect
(c) Haldane's effect
(d) Intracellular respiration
Show Answer & Explanation

Answer: (a) Chloride shift

Explanation:
1. This movement, which keeps the ionic balance, is the chloride shift.

Teacher's Note:
1. The enzyme carbonic anhydrase is abundant in RBCs.

Question 14: The binding of oxygen with haemoglobin is determined by:
(a) pH
(b) Partial pressure of oxygen
(c) Partial pressure of carbon dioxide
(d) All of the above
Show Answer & Explanation

Answer: (d) All of the above

Explanation:
1. pO2, pCO2, H+ concentration and temperature all affect Hb saturation.

Teacher's Note:
1. Interfering factors shift the dissociation curve.

Question 15: For proper transport of O2 and CO2, blood should be:
(a) Slightly acidic
(b) Strongly acidic
(c) Strongly alkaline
(d) Slightly alkaline
Show Answer & Explanation

Answer: (d) Slightly alkaline

Explanation:
1. Blood pH is about 7.4, slightly alkaline, buffered by bicarbonate.

Teacher's Note:
1. pH shifts affect Hb affinity.

Question 16: What would happen when blood is acidic?
(a) Binding of oxygen with haemoglobin increases
(b) RBCs are formed in higher number
(c) Binding of oxygen with haemoglobin decreases
(d) There is no change in oxygen binding or number of RBCs
Show Answer & Explanation

Answer: (c) Binding of oxygen with haemoglobin decreases

Explanation:
1. A high H+ concentration lowers the affinity of Hb for oxygen (Bohr effect).

Teacher's Note:
1. The curve shifts to the right.

Question 17: What happens to the O2 dissociation curve of Hb if pH decreases?
(a) Shift to the left
(b) Shift to the right
(c) Remains unchanged
(d) Oscillates erratically
Show Answer & Explanation

Answer: (b) Shift to the right

Explanation:
1. Lower pH, higher pCO2 or temperature, and more 2,3-DPG move the curve to the right.

Teacher's Note:
1. A right shift means easier release of O2 to tissues.

Question 18: The dissociation curve of oxyhaemoglobin shifts to the right when:
(a) CO2 concentration decreases
(b) CO2 concentration increases
(c) O2 concentration increases
(d) H+ concentration decreases
Show Answer & Explanation

Answer: (b) CO2 concentration increases

Explanation:
1. High pCO2 lowers Hb affinity for O2, shifting the curve to the right.

Teacher's Note:
1. Low pCO2 shifts the curve to the left.

Question 19: The oxygen-haemoglobin dissociation curve will show a right shift in case of:
(a) Less H+ concentration
(b) High partial pressure of O2
(c) Low partial pressure of CO2
(d) High 2,3-DPG
Show Answer & Explanation

Answer: (d) High 2,3-DPG

Explanation:
1. 2,3-DPG lowers Hb affinity for O2 and so shifts the curve to the right.

Teacher's Note:
1. Factors for right shift: high CO2, H+, temperature and 2,3-DPG.

Question 20: Emphysema is a condition in which:
(a) The respiratory centre is inhibited
(b) A lot of fluid collects in the lungs
(c) The walls separating the alveoli break down
(d) Lungs have more O2
Show Answer & Explanation

Answer: (c) The walls separating the alveoli break down

Explanation:
1. In emphysema the alveolar walls are damaged and the respiratory surface is reduced, often due to smoking.

Teacher's Note:
1. It is a chronic disorder.

Question 21: The rate of respiration is directly affected by:
(a) CO2 concentration
(b) O2 in the trachea
(c) Concentration of O2
(d) Diaphragm expansion
Show Answer & Explanation

Answer: (a) CO2 concentration

Explanation:
1. A rise in CO2 and H+ stimulates the chemosensitive area, increasing the rate and depth of breathing.

Teacher's Note:
1. O2 has only a minor role.

Question 22: If a man from the sea coast goes to the Everest peak, then:
(a) His breathing and heartbeat will increase
(b) His breathing and heartbeat will decrease
(c) His respiratory rate will decrease
(d) His heartbeat will decrease
Show Answer & Explanation

Answer: (a) His breathing and heartbeat will increase

Explanation:
1. Low pO2 at altitude stimulates the carotid bodies, raising the breathing and heart rate.

Teacher's Note:
1. With time, RBC count also rises.

Question 23: CO is more toxic than CO2 because it:
(a) Damages lungs
(b) Destroys haemoglobin
(c) Affects the nervous system
(d) Reduces the oxygen carrying capacity of haemoglobin
Show Answer & Explanation

Answer: (d) Reduces the oxygen carrying capacity of haemoglobin

Explanation:
1. CO combines with Hb to form stable carboxyhaemoglobin and blocks oxygen transport.

Teacher's Note:
1. The affinity of CO for Hb is about 200 times that of O2.

Question 24: Carbon monoxide has greater affinity for haemoglobin than oxygen by about:
(a) 1000 times
(b) 200 times
(c) 20 times
(d) 2 times
Show Answer & Explanation

Answer: (b) 200 times

Explanation:
1. CO binds Hb about 200 times more strongly than O2.

Teacher's Note:
1. This makes CO poisoning dangerous.

Question 25: About 97% of oxygen is transported by RBCs. The remaining 3% is:
(a) Dissolved in plasma and transported
(b) Retained in lungs
(c) Attached to cell membranes
(d) Found inside mitochondria
Show Answer & Explanation

Answer: (a) Dissolved in plasma and transported

Explanation:
1. A small amount of O2 is carried in the dissolved state in plasma.

Teacher's Note:
1. Dissolved CO2 in plasma is about 7%.

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