Question

1. Which of the following pressures must always be lower than the others in order to ensure proper lung ventilation?

• Atmospheric
• Intrapleural
• Alveolar
• Intrapulmonary

2. When blood leaves tissues that are more metabolically active than when at rest, the saturation of the hemoglobin would be:

• Exactly 75%
• 100%
• 0%
• Less than 75%

3. Hemoglobin can carry both oxygen and carbon dioxide because ---------------------

• When oxygen binds to hemoglobin, the oxygen molecule is chemically altered, making it possible for carbon dioxide to bind to the oxygen molecule.
• They bind to different sites on the hemoglobin molecule.
• Both oxygen and carbon dioxide can bind to the same site on hemoglobin at the same time.
• Actually, they can’t both be carried at the same time on hemoglobin because they compete for the same binding site.

4. Which of the following is NOT likely to increase in activity in red blood cells as they travel through pulmonary capillaries in the lungs:

• Proton (H⁺) release from hemoglobin
• Carbon dioxide binding to amino acids of hemoglobin
• Bicarbonate ion movement into the cell
• Carbonic acid conversion to carbon dioxide and water

Answer 1

1) B) Intrapleural

explanation:

Mechanics of breathing :

Following three types of pressures are observed in breathing mechanics.
1) Intrapleural pressure:
It is the pressure in the space between lungs and chest wall.
Normally it is negative around - 2.5 mmHg at the start of inspiration.

2) Intra alveolar pressure:
It is the pressure inside the alveoli.
It becomes negative during inspiration resulting in sucking of the air in the lungs and become positive during expiration resulting I exhalation of air out.

3) Transpulmonary pressure :
It is the pressure difference between intra alveolar pressure and Intrapleural pressure.

During inspiration :
- Intra alveolar pressure decreases to - 1 mmHg at the end of inspiration.

- Intrapleural pressure reaches - 6 mmHg at the end of inspiration

- Transpulmonary pressure is highest at the end of normal inspiration

- Air flows into the lungs

During Expiration :

- Intra alveolar pressure increases to + 1 mmHg at the end of expiration.

- Intrapleural pressure reaches the Normal value of -2.5 mmHg

- Air flows out of the lung

2) d) Less than 75%

explanation: metabolically more active cells utilizes more oxygen hence less oxygen remains in the blood vessels leaving the tissue.

3) D) Actually, they can’t both be carried at the same time on hemoglobin because they compete for the same binding site.

4) C) Carbon dioxide binding to amino acids of hemoglobin

explanation: Carbon dioxide binding to amino acids of hemoglobin decreases in the pulmonary capillaries