What is the partial pressure of oxygen and carbon dioxide in atmospheric air ?

Options

A. `p_(O_(2))` 159 mm Hg, `p_(CO_(2))`0.3 mm Hg
B. `p_(O_(2))` 104 mm Hg, `p_(CO_(2))`40 mm Hg
C. `p_(O_(2))` 40 mm Hg, `p_(CO_(2))`45 mm Hg
D. `p_(O_(2))` 95 mm Hg, `p_(CO_(2))`40 mm Hg

Answer

To determine the partial pressure of oxygen (O2) and carbon dioxide (CO2) in atmospheric air, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Partial Pressure**:
- Partial pressure refers to the pressure exerted by a single type of gas in a mixture of gases. It is a crucial concept in understanding how gases diffuse in the respiratory system.

2. **Atmospheric Air Composition**:
- Atmospheric air is composed of approximately 78% nitrogen, 21% oxygen, and about 0.03% carbon dioxide, along with trace amounts of other gases.

3. **Calculating Partial Pressure of Oxygen (PO2)**:
- The total atmospheric pressure at sea level is approximately 760 mmHg.
- To find the partial pressure of oxygen, we can use the formula:
\[ PO2 = (Percentage \ of \ O2) \times (Total \ Atmospheric \ Pressure) \]
- Substituting the values:
\[ PO2 = 0.21 \times 760 \ mmHg \approx 159 \ mmHg \]

4. **Calculating Partial Pressure of Carbon Dioxide (PCO2)**:
- Similarly, we can calculate the partial pressure of carbon dioxide using its percentage in the atmosphere:
\[ PCO2 = (Percentage \ of \ CO2) \times (Total \ Atmospheric \ Pressure) \]
- Substituting the values:
\[ PCO2 = 0.0003 \times 760 \ mmHg \approx 0.23 \ mmHg \]

5. **Summary of Results**:
- The partial pressure of oxygen (PO2) in atmospheric air is approximately **159 mmHg**.
- The partial pressure of carbon dioxide (PCO2) in atmospheric air is approximately **0.23 mmHg**.

### Final Answer:
- **Partial Pressure of Oxygen (PO2)**: 159 mmHg
- **Partial Pressure of Carbon Dioxide (PCO2)**: 0.23 mmHg

---