Respiration is the process by which living organisms convert food into energy. This process occurs in cells, where oxygen is used to break down glucose, a type of sugar. The result is energy, which powers various activities in the body, and carbon dioxide, which is a waste product that needs to be expelled. In humans and many animals, respiration involves breathing in air through the lungs. The oxygen from the air is absorbed into the bloodstream, while carbon dioxide is released when we exhale. This exchange of gases is essential for maintaining life and is closely linked to the function of the heart and circulatory system.