Respiration is important because it produces energy that is essential for the normal functioning of the body. Respiration provides cells with oxygen and expels toxic carbon dioxide. The BBC notes that cells need energy for movement, multiplication, the synthesis of essential molecules and maintaining body temperature.
Physiological respiration occurs across the respiratory system, which includes the upper and lower respiratory tracts. The upper respiratory tract is composed of the nasal cavity, sinuses, pharynx and larynx, while the lower respiratory tract includes the trachea, lungs, bronchi and the diaphragm. Physiological respiration is also known as ventilation and breathing, and it involves inhalation and exhalation processes. Ventilation occurs involuntarily, but a person can modify breathing. Healthline notes that respiration is important because the body cannot store oxygen. The respiratory system also warms, humidifies and filters air during gaseous exchange.
About.com reveals that energy production occurs in cells through the metabolic process of cellular respiration, which produces energy in the form of adenosine triphosphate (ATP). Cells harvest this energy from food in three stages, which are glycolysis, the citric acid cycle and electron transport. Fats contain more energy than proteins and carbohydrates. Wikipedia notes that cells use oxygen to produce energy through the process of aerobic respiration, which releases carbon dioxide as a waste product. Water is also released in metabolic respiration. Anaerobic respiration produces small amounts of energy in the absence of oxygen.