A Level Biology Practice Exam

Which blood gas is primarily measured to assess respiratory function?

1. Nitrogen

2. Hydrogen

3. Oxygen

4. Carbon Dioxide

The correct answer is: Oxygen

Measuring oxygen levels is crucial for assessing respiratory function because oxygen is essential for cellular respiration, which generates the energy needed for various bodily functions. The primary site of oxygen exchange occurs in the alveoli of the lungs, where oxygen from the inhaled air diffuses into the blood. A well-functioning respiratory system ensures adequate oxygen delivery to tissues. While other gases like carbon dioxide are also important in respiratory assessments, they are primarily measured to evaluate ventilation effectiveness and acid-base balance. In contrast, assessing oxygen levels directly indicates how well the lungs can oxygenate blood, making it a key factor in evaluating respiratory health.