Most oxygen molecules of oxygen consist of two oxygen atoms. Although oxygen is the second largest gas after nitrogen, its volume in the atmosphere is less than 1/4. Animals and plants absorb oxygen directly from the air and rely on it to release the energy stored in food in a usable form. Oxygen has other important uses. Any fuel you can think of, from gasoline in a car to candles on a birthday cake, must rely on oxygen in the burning process. Without oxygen, the fire will go out. The oxygen consumption rate is fast when burning, but it is slow in some oxygen consumption processes. For example, in the process of oxidation and rust of steel on objects such as cars, the oxygen consumption rate is very slow. After a thunderstorm, I sometimes smell a pungent smell, which is the smell of ozone. When lightning reacts with oxygen in the air, ozone is formed. Ozone is a nutrient molecule containing three oxygen atoms. Ozone can strongly absorb the ultraviolet rays of the sun, so that the creatures on the ground are not harmed, and a small amount of ultraviolet rays reaching the surface are beneficial to human beings and most creatures.
Life activities of living things need to consume energy, which comes from the oxidative decomposition of organic substances such as sugars, lipids and protein. The whole process in which organisms undergo a series of oxidative decomposition in cells, eventually producing carbon dioxide or other products, and releasing energy is called respiration!
Breathing can provide energy for the life activities of organisms. Part of the energy released by breathing is converted into heat energy and dissipated, and the other part is stored in ATP. When ATP is decomposed by enzymes, it releases stored energy for various life activities of organisms, such as cell division, plant growth, mineral element absorption, muscle contraction, nerve impulse conduction and so on. Second, the respiratory process can provide raw materials for the synthesis of other compounds in the body. Some intermediate products produced during respiration can be used as raw materials for the synthesis of some important compounds in the body. For example, pyruvate, an intermediate product of glucose decomposition, is the raw material for the synthesis of amino acids.