The partial pressure of oxygen in the alveoli of the lungs is -
- equal to that in the blood
- more than that in the blood
- less than that in the blood
- less than that of carbon dioxide
The Correct Option is B
Approach Solution - 1
Partial Pressure of Oxygen in Alveoli and Blood
The partial pressure of oxygen (\( PO_2 \)) in the alveoli of the lungs is less than that in oxygenated blood. In normal conditions, the \( PO_2 \) in the alveoli is about 104 mmHg, while the \( PO_2 \) in oxygenated blood is approximately 95 mmHg.
Alveolar Oxygen Partial Pressure:
The partial pressure of oxygen in the alveolar air is 104 mmHg. This refers to the oxygen pressure in the air present within the alveoli of the lungs. This pressure is the average \( PO_2 \) in the alveoli where oxygen is exchanged with carbon dioxide during respiration.
Variation in Partial Pressure:
The partial pressure of oxygen in the alveoli can vary depending on factors such as changes in altitude and specific conditions (e.g., respiratory diseases, lung function, or atmospheric conditions).
Approach Solution -2
Answer: more than that in the blood
Explanation:
The partial pressure of oxygen in the alveoli is higher than in the blood because oxygen is constantly being diffused from the alveoli (where the partial pressure of oxygen is higher) into the blood. This is the process of oxygenation that occurs during respiration.
- In the alveoli, the partial pressure of oxygen is typically around 100 mmHg, while in the venous blood returning from the body, the partial pressure of oxygen is around 40 mmHg.
- This difference in partial pressures allows oxygen to diffuse from the alveoli into the blood, where it binds to hemoglobin in red blood cells for transport to tissues.
- The partial pressure of oxygen in the alveoli being higher than that in the blood is crucial for the efficient exchange of gases during respiration.
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Concepts Used:
Partial Pressure
Partial Pressure is defined as if a container filled with more than one gas, each gas exerts pressure. The pressure of anyone gas within the container is called its partial pressure.
Dalton’s Law of Partial Pressure:
According to Dalton’s law of partial pressures, the total pressure exerted by the mixture of gases is the sum of the partial pressure of every existing individual gas, and every gas is assumed to be an Ideal gas.
Ptotal = P1 + P2 + P3 …
Where P1, P2, P3 are the partial pressures of gas 1, gas 2, and gas 3. Since every gas has an independent behavior, the ideal gas law is used to find the pressure of that gas if its number of moles, the volume of container and temperature is known.