The document is about respiration and contains the following key points: 1. Respiration is the process the body uses to release energy from digested food, mainly glucose. It occurs through aerobic respiration, which uses oxygen, and anaerobic respiration, which does not use oxygen. 2. The circulation system, including the blood, heart, blood vessels and lungs, transports oxygen and glucose to cells and removes waste products like carbon dioxide. 3. The breathing system, including inhalation and exhalation, takes in oxygen and expels carbon dioxide to support aerobic respiration in cells.