ATP is produced through respiration, and ATP water releases energy for use by human cells. Respiration can be divided into aerobic respiration and anaerobic respiration.

The whole process of aerobic respiration, It can be divided into three stages: In the first stage (called glycolysis), one molecule of glucose is broken down into two molecules of pyruvate. During the decomposition process, a small amount of hydrogen is produced and a small amount of energy is released. This The first stage is carried out in the cytoplasmic matrix; in the second stage (called the tricarboxylic acid cycle or citric acid cycle), pyruvate undergoes a series of reactions and decomposes into carbon dioxide and hydrogen, while releasing a small amount of energy. This stage is In the mitochondria; in the third stage (respiratory electron transport chain), the hydrogen produced in the first two stages undergoes a series of reactions and combines with oxygen to form water, while releasing a large amount of energy. This stage is also in the mitochondria Each chemical reaction in the above three stages is catalyzed by different enzymes. In the organism, after 1 mol of glucose is completely oxidized and decomposed, 2870kJ of energy is released, of which about 977kJ of energy is released. Stored in ATP (32 ATP), the rest of the energy is lost in the form of heat energy.

Anaerobic respiration generally refers to the conversion of glucose, etc. by cells under anaerobic conditions through the catalysis of enzymes. The process in which organic matter decomposes into incomplete oxidation products while releasing a small amount of energy. For higher plants, higher animals and humans, this process is called anaerobic respiration.