AIPMT AIIMS JIPMER MCAT Breathing and Exchange of Gases
1. People living at sea level have around 5 million RBC per cubic millimeter of their blood whereas those living at an altitude to 5400 metres have around 8 million. This is because at high altitude
(a) people eat more nutritive food, therefore more RBCs are formed
(b) people get pollution-free air to breathe and more oxygen is available
(c) atmospheric O2 level is less and hence more RBCs are needed to absorb the required amount of 02 to survive
(d) there is more UV radiation which enhances RBC production.
2. Although much CO, is carried in blood, yet blood does not become acidic, because
(a) it is absorbed by the leucocytes
(b) it combines with water to form H2C03 which is neutralized by Na2C05
(c) C02 transport and blood buffers play an important role in it
(d) it is continuously diffused through the tissues and is not allowed to accumulate.
3. Which one of the following statements is incorrect?
(a) The principle of counter current flow facilitates efficient respiration in gills of fishes.
(b) The residual air in lungs slightly decreases the efficiency of respiration in mammals.
(c) The presence of non-respiratory air sacs, increases the efficiency of respiration in birds.
(d) In insects, circulating body fluids serve to distribute oxygen to tissues.
4. When temperature decreases oxy – Hb curve will i become
(a) more steep (b) straight
(c) parabola (d) all of these.
5. What is the approximate normal composition of alveolar air?
(a) 14% oxygen, 5% carbon dioxide, 75% nitrogen
(b) 21% oxygen, 2% carbon dioxide, 77% nitrogen
(c) 16% oxygen, 3% carbon dioxide, 81% nitrogen
(d) 10% oxygen, 8% carbon dioxide, 82% nitrogen.
6. At rest body produces C02 at the rate of
(a) 100cc/min (b) 200cc/min
(c) 400 cc/min (d) 600 cc/min.
7. With reference to human respiration, which is correct?
(a) Pulmonary ventilation is equal to alveolar ventilation.
(b) Alveolar ventilation is less than pulmonary ventilation.
(c) Alveolar ventilation is more than pulmonary ventilation
(d) Pulmonary ventilation is less than alveolar ventilation.
8. If alveolar ventilation is 4200 mL/min, respiratory frequency is 12 breaths per minute, and tidal volume is 500 mL, what is the anatomical-dead-space ventilation?
(a) 1800 mL/min
(b) 6000 mL/min
(c) 350 mL/min
(d) 1200 mL/min
9. Human beings have a significant ability to maintain and moderate the respiratory rhythm to suit demands of the body. For it we have
(i) Respiratory rhythm centre in medulla – R
(ii) Pneumotaxic centre in pons – PT
(iii) Chemosensitive area in medulla – C1
(iv) Peripheral chemoreceptors in aortic arch and carotid artery- C2
Find out the correct path for regulation of respiration.
Where in the body will haemoglobin be saturated at the percentages shown at points 1, 2 and 3 on the graph?11. After taking a long deep breath we do not respire for some seconds due to
(a) more CO2 in blood (b) more O2 in blood
(c) less CO2 in blood (d) less O2 in blood.
12. Foetal haemoglobin has X affinity for oxygen than that of mother’s haemoglobin during gestation. X is
(d) lower affinity earlier but higher later.
13. Which of the following is incorrect about the given graph?
(a) The curve is called oxygen dissociation curve.
(b) The part ‘A’ represents percentage saturation of haemoglobin with oxygen.
(c) The part ‘B’ represents partial pressure of carbon dioxide.
(d) This curve is highly useful in studying the effect of factors like pC02, H+ concentration, etc.
14. Haldane effect plays more important role in promoting carbon dioxide transport than that of the Bohr’s effect in promoting oxygen transport because
(a) oxyhaemoglobin is a stronger acid which donates hydrogen ion (H+) which in turn displace carbon dioxide from blood
(b) carbaminohaemoglobin is a stronger acid which splits into hydrogen ion (H+) and bicarbonate (HCO3–)
(c) carbon dioxide reacts with water to form carbonic acid that lowers the pH in tissue
(d) carbon dioxide is less soluble in venous blood than in arterial blood.
15. Inspiration occurs when there is a negative pressure in the lungs with respect to atmospheric pressure. This negative pressure is achieved when
(a) intrapulmonary pressure is less than the atmospheric pressure
(b) intrapulmonary pressure is greater than the atmospheric pressure
(c) intrapulmonary pressure is equal to the atmospheric pressure
(d) intrapleural pressure becomes more than the intra alveolar pressure.
True or False type questions
16. The PO; and PCO. in the deoxygenated blood and in the tissues is same, that is 40mm Hg and 45 mm Hg respectively.
17. Nearly 200 mL of air remains in the lungs even after a forcible expiration, which is called RV or residual volume.
18. The factors favourable for dissociation of oxygen from oxyhaemoglobin are high PCO2 low PO2 and low H+ concentration.
19. Receptors associated with aortic arch and carotid artery can recognize changes in CO2 and H+ concentration.
20. Every 100 mL of oxygenated blood can deliver around 4 mL of oxygen to the tissues under normal physiological conditions.
21. RBCs can transport about 97 percent of oxygen as well as 20-25 percent of carbon dioxide.
22. Although solubility of CO2 is 20-25 times higher than that of O2 the amount of CO2 that diffuses through diffusion membrane, per unit difference in partial pressure is the same as that of O2.
23. IC increases as a result of increase in IRV.
24. A decrease in pulmonary volume decreases the intrapulmonary pressure to less than the atmospheric pressure, which causes air from outside to rush inside.
25. The conducting part of the respiratory system transports the atmospheric air to alveoli, clears it from foreign particles, removes excess moisture and brings it to body temperature.
Match the Columns
26. Match Column-I with Column-ll and select the correct option from the codes given below.
Passage Based Questions
28.(A) Complete the given passage with appropriate words or phrases.
Oxygen in the inhaled air is nearly in alveolar air, it is (ii). while in exhaled air, it is (iii) .
Carbon dioxide in the inhaled air is (iv). in alveolar air is (v). while in the exhaled air, it is (vi) .
(B) Read the passage and correct the errors, wherever present.
In tissues, PO, blood is 45mm Hg, that of interstitial fluid is 45mm Hg, while in cells around, it is 32mm Hg. The blood leaving the tissue capillaries has PO?equal to45mmHg. However, nearly 50-55% of haemoglobin is still in oxygenated form.
Assertion & Reason Type Questions
In each of the following questions, a statement of Assertion is given and a corresponding statement of Reason is given just below it. Of the statements, mark the correct answer as :
(a) if both A and R are true and R is the correct explanation of A
(b) if both A and R are true but R is not the correct explanation of A
(c) if A is true but R is false
(d) if both A and R are false.
29. Assertion : 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.
Reason : The anatomical setup of lungs in thorax is such that any change in the volume of lungs will be reflected in the thoracic cavity.
30. Assertion: The diaphragm, intercostal muscles and abdominal muscles play an important role in inspiration.
Reason : The contraction of the phrenic muscles, external intercostal muscles and abdominal muscles help in inspiration.
31. Assertion : TV or tidal volume is the volume of air inspired or expired during normal breath.
Reason : Both TLC and VC include TV.
32. Assertion : Mammals have negative pressure breathing.
Reason : It allows them to eat and breathe at the same time.
33. Assertion : In human males, lateral movement of thorax constitutes 25% of breathing, while abdominal movement accounts for 75% of breathing.
Reason : In human females, the entire breathing is through lateral movement of thorax.
34. Assertion : The quantities of air the lungs can receive, hold or expel under different conditions are called pulmonary volumes, while the combination of 2 or more pulmonary volumes are called pulmonary capacities.
Reason : All pulmonary volumes and capacities are about 20-25 percent less in women.
35. Assertion : According to Bohr’s effect, an increase in carbon dioxide in the blood causes oxygen to be displaced from the haemoglobin.
Reason: All the factors which shift oxygen haemoglobin dissociation curve to the left increase Bohr’s effect.
36. Assertion : According to Haldane effect, binding of oxygen with haemoglobin tends to displace carbon dioxide from the blood.
Reason : It is quantitatively far more important in promoting C02 transport than the Bohr effect in promoting 02 transport.
37. Assertion: The dorsal respiratory group (DRG) present in the dorsal portion of medulla oblongata mainly causes expiration.
Reason : The ventral respiratory group (VRG) on the ventrolateral part of medulla oblongata mainly controls inspiration.
38. Assertion : After strenuous exercise, the amount of oxygen consumed is enormously high.
Reason : A part of this oxygen is used for reformation of glucose from lactic acid accumulated in muscles during exercise.
Figure Based Questions
39. Refer to the figure below and identify the labelled parts – A, B, C, D, E and F.
40. Fill in the blanks using the letters above.
1. The maximum volume of air, a person can breathe in after a forced expiration, is called Jj]_.
2. TLC includes (ii) and (iii).
3. (iv) is forced inspiration.
4. (v) is forced expiration.
5. (vi) is TLC minus (vii).
I. (c) 2. (c) 3. (d) 4. (a) 5. (a)
6. (b) 7. (b) 8. (a) 9. (b) 10. (c)
II. (c) 12. (b) 13. (c) 14. (a) 15. (a)
17. False. Residual volume is 1100 mL to 1200 mL.
18. False. It is increase in H+ concentration and decrease in pH.
20. False. It is 5mL of oxygen transported to the tissues under normal physiological conditions.
22. False. CO, diffuses 20 times faster than oxygen.
24. False. An increase in thoracic volume decreases the pressure resulting in negative pressure.
25. False. It adds moisture and humidifies the air.
26. A-(vii), B-(v), C-(i), D-(vi), E-(ii), F-(iii), G-(iv)
27. A-(i, xi), B-(v, x), C-(vi, ix), D-(vii, viii), E-(iv, xii), F-(iii, xiii), G-(ii, xiv)
28. (A) (i) 20.84%, (ii) 13.6%, (iii) 15.7%, (iv) 0.03-
0.04%, (v) 5.3%, (vi) 3.6-4.0%.
(B) In tissues, PO. blood is 45mm Hg 95mm Hg, that of interstitial fluid is 45mm Hg 40mm Hg, while in cells around, it is 32mm Hg 23mm Hg. The blood leaving the tissue capillaries has PO, equal to 45mm H§-40mm Hg. However, nearly 50-55% 70-75% of haemoglobin is still in oxygenated form.
29. (c) 30. (c) 31. (b) 32. (a) 33. (c)
34. (b) 35. (c) 36. (b) 37. (d) 38. (a)
39. A – Inspiratory capacity B – Residual volume C – Inspiratory reserve volume D – Vital capacity E – Expiratory reserve volume F – Functional residual capacity
40. 1. (i) (D); 2. (ii) (D) (iii) B; 3. (iv) C; 4. (v) E; 5. (vi) D; (vii) B