Emergency Medical Technician (EMT) Intermediate Practice Exam

During pulmonary respiration, which of the following process occurs?

1. Oxygen diffuses into the bloodstream

2. Carbon dioxide diffuses into the alveoli

3. Carbon dioxide is converted to bicarbonate

4. Oxygen is entirely consumed

The correct answer is: Carbon dioxide diffuses into the alveoli

The process of pulmonary respiration primarily involves two key gas exchanges that occur in the alveoli of the lungs. When air reaches the alveoli, oxygen present in the inhaled air diffuses across the alveolar membrane and into the bloodstream. Concurrently, carbon dioxide, which is a waste product of cellular metabolism, diffuses from the blood into the alveoli to be exhaled. This exchange ensures that oxygen is delivered to the tissues while carbon dioxide is removed. The correct answer identifies that carbon dioxide diffuses into the alveoli, which is a crucial aspect of respiratory function. This removal of carbon dioxide is essential for maintaining the body's acid-base balance and preventing respiratory acidosis. While the other options mention aspects of respiration, they do not accurately capture this specific mechanism occurring during pulmonary respiration. For instance, while oxygen diffusion into the bloodstream does occur, it does not represent the unique process highlighted in the question. Similarly, the conversion of carbon dioxide to bicarbonate is a separate metabolic process mainly occurring in the blood rather than during pulmonary respiration, and the idea that oxygen is entirely consumed is misleading, since there is often residual oxygen remaining in the blood after gas exchange has taken place. Thus, the identified diffusion of carbon dioxide into the alveoli stands out