Free Respiration MCQs with Answers

51. The Bohr effect describes

• A. O2 binding to hemoglobin
• B. Effect of CO2/pH on O2 affinity
• C. CO2 transport
• D. Lung compliance

Explanation: The Bohr effect states that increased CO2/decreased pH reduces hemoglobin's affinity for O2, facilitating O2 release to tissues.

52. Most CO2 is transported as

• A. Dissolved in plasma
• B. Carbaminohemoglobin
• C. Bicarbonate ions
• D. Free CO2

Explanation: About 70% of CO2 is transported as bicarbonate (HCO3-) in plasma, formed by carbonic anhydrase in RBCs.

53. Tidal volume is approximately

• A. 500 mL
• B. 3000 mL
• C. 1200 mL
• D. 6000 mL

Explanation: Tidal volume (air in normal breath) is about 500 mL at rest in healthy adults.

54. The respiratory center is located in the

• A. Cerebrum
• B. Cerebellum
• C. Medulla oblongata
• D. Hypothalamus

Explanation: The respiratory center in the medulla oblongata controls breathing rate and depth.

55. Hemoglobin has highest affinity for O2 when

• A. pH is low
• B. CO2 is high
• C. pH is high
• D. Temperature is high

Explanation: Hemoglobin has highest O2 affinity at high pH, low CO2, and low temperature (in the lungs).

56. The chloride shift occurs to

• A. Maintain electrical neutrality
• B. Increase O2 transport
• C. Decrease CO2
• D. Activate enzymes

Explanation: As HCO3- leaves RBCs, Cl- enters to maintain electrical neutrality (chloride shift or Hamburger shift).

57. Asthma is characterized by

• A. Emphysema
• B. Bronchoconstriction and inflammation
• C. Lung cancer
• D. Pneumonia

Explanation: Asthma involves bronchoconstriction, airway inflammation, and excess mucus production, causing wheezing and dyspnea.

58. The primary function of larynx is:

• A. Humidifying air
• B. Filtering dust
• C. Gaseous exchange
• D. Voice production

Explanation: The larynx houses the vocal cords, and air forced between them makes them vibrate to produce sound, which is why it is called the voice box. Humidifying and filtering the air are done earlier, in the nasal cavity and the ciliated mucous lining of the airways. Gaseous exchange happens only in the alveoli, since no other part of the tract has walls thin enough.