Khyber Medical University- MDCAT 2024 CODE:

A MCQs: 100 Time: 3.5 hours No Negative Marking

1) Which mechanism primarily facilitates a. Decrease in temperature

oxygen transport in the blood? b. Increase in blood pH
a. Dissolved in plasma c. Increase in carbon dioxide
b. Bound to hemoglobin concentration
c. As bicarbonate ions d. Increase in oxygen tension
d. Direct diffusion 8) During expiration, the diaphragm:
2) The primary site for gas exchange in a. Contracts
the lungs is found in: b. Relaxes
a. Bronchi c. Expands
b. Trachea d. Remains static
c. Alveoli 9) What physiological condition is
d. Bronchioles indicated by a decrease in blood pH
3) What role does the enzyme carbonic and increased respiration rate?
anhydrase play in respiration? a. Acidosis
a. Converts carbon dioxide and b. Alkalosis
water into carbonic acid c. Hyperventilation
b. Facilitates oxygen release from d. Hypoventilation
hemoglobin 10) Which statement correctly
c. Regulates breathing rate reflects the function of the pleural
d. Promotes mucus production membranes?
4) What respiratory structure is primarily a. They increase lung elasticity
responsible for filtering and moistening during inhalation.
inspired air? b. They allow for gas exchange in
a. Larynx the lungs.
b. Nasal cavity c. They provide a lubricated
c. Trachea surface for lung movement.
d. Alveoli d. They filter out particles in
5) What is the function of surfactant in inhaled air.
the alveoli? 11) What is the significance of the
a. Enhances gas exchange by oxygen-hemoglobin dissociation curve
increasing surface area being sigmoidal?
b. Reduces surface tension to a. It indicates cooperative binding
prevent alveolar collapse of oxygen.
c. Aids in the filtration of air b. It reflects linear binding of
d. Stores oxygen for later use oxygen to hemoglobin.
6) The primary driver of the respiratory c. It represents the sole function of
rate is detected by: myoglobin.
a. Baroreceptors d. It suggests constant metabolic
b. Chemoreceptors that sense activity.
carbon dioxide levels 12) What is the normal tidal volume
c. Thermoreceptors for an average adult?
d. Mechanoreceptors a. Approximately 200 ml
b. Approximately 500 ml
c. Approximately 1 liter
7) What factor increases the release of d. Approximately 2 liters
oxygen from hemoglobin at the tissue 13) The movement of oxygen from
level? the alveoli into the blood occurs
primarily by:
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a. Active transport a. Charles’s Law
b. Filtration b. Boyle’s Law
c. Simple diffusion c. Dalton’s Law
d. Bulk flow d. Henry’s Law
14) What is the role of intercostal 20) The majority of carbon dioxide in
muscles during breathing? the blood is transported as:
a. They assist primarily in forced a. Carbonic acid
expiration. b. Bicarbonate ions
b. They support only passive c. Bound to hemoglobin
inhalation. d. Dissolved in plasma
c. They enhance ventilation by 21) What does the term "vital
expanding the thoracic cavity. capacity" refer to?
d. They play no role in the a. The maximum amount of air that
respiratory process. can be exhaled after taking the
15) An increase in carbon dioxide deepest breath possible
levels in the blood typically leads to: b. Total air in the lungs after
a. Decreased respiratory rate maximal inhalation
b. Decreased oxygen affinity c. Air remaining in the lungs after
c. Increased oxygen retention normal expiration
d. Increased respiratory rate d. The amount of air exchanged in
16) The primary component of one breath
surfactant responsible for reducing 22) In which part of the body is the
surface tension is: majority of oxygen carried bound to
a. Phospholipids hemoglobin?
b. Proteins a. Lungs
c. Carbohydrates b. Heart
d. Cholesterol c. Blood
17) What defines the residual d. Tissues
volume in the lungs? 23) Which respiratory condition is
a. The volume of air that can be characterized by the inflammation of
forcibly exhaled the bronchi?
b. The volume of air remaining in a. Asthma
the lungs after maximal b. Bronchitis
exhalation c. Emphysema
c. The total volume of air that can d. Pneumonia
be inhaled 24) What drives the diffusion of
d. The normal tidal volume oxygen across the alveolar membrane?
18) In a healthy adult, the average a. Hydrostatic pressure
total lung capacity is approximately: b. Concentration gradient
a. 3 liters c. Active transport
b. 5 liters d. Electrochemical gradient
c. 7 liters
d. 10 liters

25) What change occurs in the lungs

19) Which gas law describes the
during an asthma attack?
relationship between the pressure and
a. Airway dilation
volume of a gas in the lungs?

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b. Excessive mucus production and 31) What primarily regulates the pH
airway constriction levels in the blood through respiratory
c. Decreased effort in respiration function?
d. Increased lung compliance a. Metabolic waste products
26) The primary role of the b. Oxygen levels
diaphragm during breathing is to: c. Carbon dioxide levels
a. Stabilize the rib cage d. Blood volume
b. Increase thoracic volume during 32) Which of the following lung
inhalation volumes cannot be measured directly
c. Increase pressure in the using a spirometer?
abdominal cavity a. Tidal volume
d. Decrease lung volume during b. Vital capacity
expiration c. Residual volume
27) An increase in airflow d. Inspiratory reserve volume
obstruction is most often associated 33) What role do alveolar
with which physiological condition? macrophages play in the respiratory
a. Restrictive lung disease system?
b. Obstructive lung disease a. Carry oxygen to tissues
c. Pulmonary edema b. Produce surfactant
d. Respiratory alkalosis c. Remove pathogens and debris
28) What is the primary advantage from alveoli
of the high surface area of alveoli in d. Facilitate gas exchange
the lungs? 34) What happens to breathing
a. Enhanced mucus production patterns during hypoxia?
b. Improved flexibility of lung a. Breathing rate decreases
tissues b. Breathing rate increases
c. Maximized gas exchange c. Breathing becomes irregular
efficiency d. No change occurs
d. Increased lung capacity 35) The main reason for the high
29) Which physiological factor solubility of carbon dioxide in plasma
influences the effectiveness of gas compared to oxygen is:
exchange during high-intensity a. Its lower molecular weight
exercise? b. Its higher partial pressure in
a. Decreased temperature tissues
b. Increased carbon dioxide c. Its chemical properties that
production favor solubility
c. Increased hemoglobin count d. Its lighter gas composition
d. Decreased breathing rate 36) Which structure prevents food
30) How does smoking affect the from entering the respiratory tract
respiratory system’s alveolar capacity? during swallowing?
a. Increases surface area a. Uvula
b. Decreases lung compliance b. Glottis
c. Improves gas exchange c. Epiglottis
d. Enhances the production of d. Larynx
surfactant 37) What happens to the thoracic
cavity during inhalation?
a. It contracts
b. It expands

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c. It remains unchanged c. The amount of air remaining
d. It rectifies after normal expiration
38) What is the term used to d. The sum of tidal volume and
describe the volume of air that can be residual volume
forcibly inhaled after a normal
inhalation?
a. Tidal volume 44) The primary chemical mediator
b. Inspiratory reserve volume that drives the increase in respiratory
c. Expiratory reserve volume rate during intense exercise is:
d. Vital capacity a. Oxygen
39) What is the primary function of b. Carbon dioxide
the conducting zone of the respiratory c. Nitric oxide
system? d. Lactic acid
a. Gas exchange 45) What happens to the
b. Filtration and humidification of concentration of carbon dioxide in the
air blood during hyperventilation?
c. Regulation of blood pH a. It decreases
d. Oxygen storage b. It increases
40) How does the respiratory system c. It remains unchanged
assist the body in thermoregulation? d. It fluctuates widely
a. By producing heat during 46) The term 'dead space' in
metabolism respiration refers to:
b. Through the evaporation of a. Areas of the lung where no gas
water during exhalation exchange occurs
c. By restricting airflow in cold b. The volume of air in the lungs
environments after maximal exhalation
d. By adjusting blood flow to the c. The amount of lung tissue that
skin does not participate in
41) The primary regulator of ventilation
ventilation rate is primarily influenced d. The alveoli that are not perfused
by which type of receptors? 47) Which factor contributes
a. Baroreceptors significantly to the efficiency of gas
b. Chemoreceptors exchange in the respiratory system?
c. Thermoreceptors a. High blood flow to the lungs
d. Proprioceptors b. Thin alveolar membranes
42) What respiratory condition is c. A steep diffusion gradient for
characterized by alveolar damage and gases
reduced elasticity? d. All of the above
a. Chronic bronchitis 48) During exercise, muscles utilize
b. Asthma oxygen more effectively due to:
c. Emphysema a. Decreased capillary density
d. Pneumonia b. Increased blood flow to active
43) The vital capacity of a lung is tissues
generally considered to be: c. Inhibition of oxygen diffusion
a. The total air capacity of lungs d. Decreased metabolic activity
b. The maximum amount of air that 49) What effect does an increase in
can be expelled after a maximal arterial carbon dioxide have on the
inhalation respiratory center in the brain?

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a. It leads to decreased breathing b. Decreased oxygen saturation
effort. due to lower partial pressure of
b. It stimulates the respiratory oxygen
center to increase ventilation. c. No change in oxygen saturation
c. It has no effect on breathing levels
patterns. d. Increased oxygen carry capacity
d. It reduces the sensitivity of due to increased hemoglobin
chemoreceptors. production
55) The ability of hemoglobin to bind
with oxygen is influenced by:
50) Which condition is caused by a a. Temperature
decrease in alveolar surface area? b. pH levels
a. Chronic bronchitis c. Carbon dioxide concentration
b. Pulmonary edema d. All of the above
c. Emphysema
d. Asthma
51) What effect does the curvature
of the diaphragm have during
56) Respiratory distress in children
inhalation?
often occurs due to:
a. It increases thoracic pressure.
a. Developmental growth
b. It decreases thoracic volume.
b. Immature respiratory control
c. It flattens and increases the
centers
volume of the thoracic cavity.
c. Inefficient oxygen transport
d. It disrupts airflow through the
d. Physiological stress
trachea.
57) What initiates the process of
52) The primary respiratory pathway
inhalation?
for air moving from the atmosphere
a. A decrease in pulmonary
into the lung is:
pressure
a. Nasal cavity → Bronchioles →
b. The contraction of the
Alveoli
diaphragm
b. Bronchi → Trachea → Alveoli
c. Abdominal muscle contraction
c. Trachea → Bronchi → Lungs
d. The closure of the epiglottis
d. Nasal cavity → Trachea → Alveoli
58) Which of the following
53) In pulmonary circulation, how is
mechanisms allows for carbon dioxide
blood oxygenated?
removal from the bloodstream?
a. By contact with alveolar
a. Active transport through cell
epithelium
membranes
b. Through diffusion from
b. Bulk flow in the circulatory
pulmonary capillaries
system
c. During the passage through
c. Diffusion across the alveolar-
bronchial arteries
capillary membrane
d. Via alveolar macrophages
d. Osmosis through the respiratory
54) What is a potential consequence
epithelium
of high altitude on oxygen saturation of
59) During expiration, the volume of
arterial blood?
the thoracic cavity typically:
a. Increased oxygen saturation due
a. Increases
to lower pressure
b. Decreases
c. Remains constant
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d. Expands unevenly a. Delivery decreases due to
60) How is oxygen primarily utilized increased affinity
by cells during metabolism? b. Delivery increases due to
a. For hormone regulation decreased affinity
b. As a substrate in glycolysis c. Delivery remains unchanged
c. To produce ATP via cellular d. Delivery becomes more efficient
respiration 67) The presence of which factors
d. For ion transport can lead to impaired gas exchange in
61) What physiological response the lungs?
occurs during a forced exhalation? a. Edema and inflammation
a. The diaphragm contracts b. Increased ventilation
b. The abdominal muscles contract c. Increased blood flow
c. Intrapulmonary pressure d. Optimal surfactant levels
decreases 68) Which gas has the highest
d. The thoracic cavity expands affinity for hemoglobin?
62) Which component of blood is a. Oxygen
responsible for transporting respiratory b. Carbon dioxide
gases? c. Nitric oxide
a. Plasma proteins d. Carbon monoxide
b. Erythrocytes 69) What occurs to blood vessels in
c. Leukocytes the lungs during hypoxia?
d. Platelets a. Vasodilation occurs
63) What is the effect of chronic b. Vasoconstriction occurs
obstructive pulmonary disease (COPD) c. No change in vessel diameter
on lung function? d. Increased blood flow
a. Increased lung compliance 70) Which lung structures assist in
b. Reduced airflow and gas regulating airflow and resistance?
exchange efficiency a. Alveoli
c. Improved lung elasticity b. Bronchioles
d. Decreased tidal volume c. Trachea
64) What term describes the d. Pleura
maximum amount of air that can be 71) What change occurs in lung
forcibly exhaled after a maximal function due to aging?
inhalation? a. Increased lung elasticity
a. Tidal volume b. Decreased total lung capacity
b. Inspiratory reserve volume c. Enhanced gas exchange
c. Vital capacity d. Improved respiratory rate
d. Expiratory reserve volume 72) During metabolic activities,
65) How does the respiratory system increased levels of CO2 in tissues
utilize feedback mechanisms? influence which response?
a. To stabilize blood pH levels a. Decrease in respiratory rate
b. To maintain arterial blood b. Increase in oxygen uptake
pressure c. Increase in heart rate
c. To regulate heart rate d. No significant change in
d. To alter metabolic rates breathing patterns
66) What happens to oxygen 73) In a state of acidosis, how does
delivery when body temperature rises? the body typically respond
physiologically?

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a. Decreased breathing rate 79) The presence of which condition
b. Increased breathing rate to indicates a need for supplemental
expel carbon dioxide oxygen?
c. Stabilization of blood pH through a. Hypercapnia
metabolic changes b. Hypoxemia
d. Decreased carbon dioxide levels c. Hypocapnia
74) What is the relationship between d. Hypertension
the surface area of alveoli and gas 80) Tidal volume is defined as the
exchange efficiency? amount of air:
a. Direct relationship; larger area a. Exhaled during forced breathing
facilitates better exchange b. Inhaled and exhaled during
b. Inverse relationship; larger area normal breathing
hinders exchange c. Remaining after expiration
c. No significant relationship d. Used for gas exchange
d. Surface area only affects oxygen 81) The primary way through which
levels the body increases ventilation during
75) The effect of gravity on lung exercise is by:
volumes is most pronounced in: a. Decreasing tidal volume
a. The upper lung zones b. Increasing respiratory rate
b. The lower lung zones c. Decreasing airway resistance
c. Both upper and lower equally d. Altering blood pressure
d. No effect of gravity 82) Which respiratory condition is
defined by excessive mucus secretion
due to airway inflammation?
a. Asthma
b. Chronic bronchitis
76) What blood condition can arise c. Emphysema
from prolonged exposure to low oxygen d. Pneumonia
levels?
a. Respiratory alkalosis
b. Metabolic acidosis
83) At high altitudes, the body
c. Polycythemia
responds to lower oxygen levels
d. Anemia
primarily by:
77) Which of the following describes
a. Decreasing cardiac output
the role of the medulla oblongata in
b. Stimulating increased red blood
respiration?
cell production
a. It filters particulates from
c. Enhancing lung compliance
inspired air.
d. Fewer capillary networks
b. It regulates the rate and depth
84) The sound produced during
of breathing.
normal exhalation is primarily caused
c. It produces surfactant.
by:
d. It stores excess oxygen.
a. Closure of the vocal cords
78) What effect does physical
b. Turbulence in the upper airway
exertion have on the blood flow to the
c. Fluttering of the diaphragm
lungs?
d. Movement of air through bronchi
a. Decreases blood flow
85) Increased levels of lactic acid
b. Increases blood flow
during intense activity influence
c. No effect on flow
breathing by:
d. Stabilizes flow
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a. Decreasing respiratory rate a. Arterial blood gas analysis
b. Increasing the elimination of b. Pulse oximetry
carbon dioxide c. Spirometry
c. Reducing oxygen utilization d. CO2 monitors
d. Slowing down metabolism 93) Which factor contributes to the
86) How do the lungs respond to high partial pressure of oxygen within
hypercapnia? alveoli?
a. Increase in bronchial dilation a. Room air composition
b. Stimulation of increased b. Atmospheric pressure
respiration rate c. Ventilation rates
c. Occurrence of respiratory d. All of the above
alkalosis 94) The increased respiratory rate
d. Stabilization of blood pH during exercise is primarily due to:
87) What describes the primary a. Decreased oxygen demand at
exchange function of alveoli? tissues
a. Regulation of blood pressure b. Direct stimulation of the
b. Filtration of pathogens respiratory rate by muscles
c. Gas exchange between air and c. Increased carbon dioxide
blood production
d. Control of respiratory rate d. Reduced blood flow to the lungs
88) The rate of oxygen diffusion is 95) What lung volume measures the
primarily influenced by: air left in the lungs after normal
a. Atmospheric pressure exhalation?
b. Surface area of alveoli a. Tidal volume
c. Thickness of alveolar membrane b. Residual volume
d. All of the above c. Functional residual capacity
89) Which muscle assists with both d. Inspiratory reserve volume
inhalation and forced exhalation? 96) The role of the respiratory
a. Diaphragm system includes which of the following?
b. Rectus abdominis a. Gas exchange
c. External Intercostals b. Regulation of blood pH
d. Pectoralis major c. Humidification of inspired air
d. All of the above

90) What effect does an obstruction

(like in asthma) have on airflow? 97) What physiological change
a. Increased airflow occurs with prolonged exposure to high
b. Normal airflow altitudes?
c. Decreased airflow a. Increase in heart rate
d. No effect b. Decrease in hemoglobin
91) The volume of blood that flows synthesis
through the lungs at rest is known as: c. Survival adaptation through
a. Cardiac output increased red blood cell count
b. Pulmonary blood flow d. Increase in tidal volume
c. Alveolar ventilation rate 98) The primary advantage of a
d. Systemic circulation lower pH in tissues during metabolism
92) Oxygen saturation levels can be is:
accurately measured using:

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a. Facilitating oxygen binding to 10. C
hemoglobin 11. A
b. Promoting carbon dioxide 12. B
retention 13. C
14. C
c. Enhancing oxygen unloading
15. D
from hemoglobin
16. A
d. Increasing aerobic metabolism 17. B
99) What defines the role of 18. B
bronchioles in the respiratory system? 19. B
a. Primary site for gas exchange 20. B
b. Airway resistance regulation 21. B
c. Gas filtration 22. C
d. Oxygen transportation 23. B
24. B
100) Which of the following conditions
25. B
would lead to increased secretion of
26. B
mucus in the airways?
27. B
a. Chronic bronchitis 28. C
b. Normal respiration 29. B
c. Exercise 30. B
d. High altitude 31. C
32. C
33. C
34. B
35. C
36. C
37. B
38. B
39. B
40. B
41. B
42. C
43. B
44. B
45. A
46. A
47. D
48. B
49. B
50. C
51. C
52. B
Correct Answers 53. A
1. B 54. B
2. C 55. D
3. A 56. B
4. B 57. B
5. B 58. C
6. B 59. B
7. C 60. C
8. B 61. B
9. A 62. B

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63. B
64. B
65. A
66. B
67. A
68. D
69. B
70. B
71. B
72. B
73. B
74. A
75. B
76. C
77. B
78. B
79. B
80. B
81. B
82. B
83. B
84. B
85. B
86. B
87. C
88. D
89. B
90. C
91. B
92. B
93. D
94. C
95. C
96. D
97. C
98. C
99. B
100. A

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