A Level Biology Practice Exam

What biological process is primarily associated with the respiratory system?

1. Digestion of food

2. Breathing and gas exchange

3. Blood circulation

4. Nutrient absorption

The correct answer is: Breathing and gas exchange

The biological process primarily associated with the respiratory system is breathing and gas exchange. This process involves taking in oxygen from the environment and expelling carbon dioxide, which is a byproduct of cellular metabolism. The respiratory system includes structures such as the lungs, trachea, and alveoli that facilitate this exchange of gases. During inhalation, air enters the lungs and oxygen diffuses across the alveolar walls into the bloodstream, where it binds to hemoglobin in red blood cells. Conversely, carbon dioxide diffuses from the blood into the alveoli to be exhaled. This essential function supports cellular respiration throughout the body, providing the necessary oxygen for aerobic metabolism and removing carbon dioxide to maintain homeostasis. While the other processes listed, like digestion, blood circulation, and nutrient absorption, are critical biological functions, they are not primarily associated with the lungs or respiratory processes. Instead, these processes are managed by different organ systems in the body, such as the digestive and circulatory systems.