OXYGEN.In the process of respiration, the component of air USED is oxygen. Respiratory System:Respiration is a catabolic process in which the respired oxygen is used in the oxidation of food resulting in the release of ENERGY. The overall passage of air in humans is as follows: Nostrils–Pharynx–Larynx–Trachea–Bronchi– Bronchioles – Alveoli–Cells–Blood.Humans inhale oxygen and give out Carbon dioxide.Types of Respiration:Aerobic RespirationThe respiration which takes place in the presence of oxygen is known as aerobic respiration.In this process, in fact, each glucose MOLECULE is converted into two molecules of pyruvic acid by the process, called glycolysis.Anaerobic RespirationThe respiration which takes place in the absence of oxygen is known as anaerobic respiration.In this process, the respiratory substances are incompletely oxidized to carbon dioxide and alcohol.For artificial respiration mixture of oxygen and helium gas cylinder used.It is called Heliox. Plants take carbon dioxide and give out oxygen, EXACTLY opposite to humans.