A Level Biology Practice Exam

The lungs are the primary organs involved in respiration. They play a crucial role in the process of gas exchange, which is essential for supplying oxygen to the blood and removing carbon dioxide from the body. During inhalation, the lungs expand, allowing oxygen-rich air to enter, and during exhalation, they contract to expel carbon dioxide-rich air. This exchange takes place in tiny air sacs called alveoli, where oxygen diffuses into the blood while carbon dioxide diffuses out to be exhaled.

In contrast, the heart is vital for circulating blood throughout the body but does not directly participate in gas exchange. The liver is involved in metabolism and detoxification rather than respiration, and while the kidneys help regulate the body's fluids and remove waste products, they do not play a direct role in the respiratory process. Thus, the lungs are specifically adapted for respiration, making them the primary organs involved in this vital function.