Breathing and respiration are interrelated biological processes; however, breathing is a physical mechanism, while respiration has many chemical reactions involved.
Breathing is an extracellular process in which the exchange of oxygen and carbon dioxide gases happen using inhalation and exhalation processes. The process of gas exchange occurs in the lungs (or gills of fish), but there are other parts of the respiratory system involved as well. Also, breathing is considered as a voluntary process which can be controlled consciously, but the breathing muscles are controlled automatically from the brainstem. Breathing also produces no energy in the form of ATP and involves no enzymatic reactions or metabolic pathways. Inhalation is an active process which needs energy while exhalation is a passive process in which no energy is needed for pushing air out of the body.
Inhalation allows the intake of oxygen gas in the body via the following route: nasal cavity, mouth, pharynx, trachea, bronchi, bronchioles and alveoli where this inhaled oxygen is absorbed in the blood within the surrounding capillaries. This inhaled oxygen is then delivered to different parts of the body where respiration takes place. Moreover, intercostal muscles and diaphragm contract that flattens the diaphragm and increases the volume in thoracic cavity, leading to a decrease in pressure in the lungs. The rib cage also rises upwards. Hence, oxygen diffuses inside the body. On the other hand, exhalation involves the removal of carbon dioxide (waste product of respiration) from the blood because the air is forced out of the body due to decrease in volume of the thoracic cavity and an increase in the pressure within the lungs. The intercostal muscles relax, and the diaphragm as well due to which it arches upwards, and the rib cage drops downwards.
Respiration is an intracellular process that includes different metabolic pathways and enzymes which play an integral role in its different stages. Respiration takes place in the cytosol and mitochondria of the cells, and releases a lot of energy in the form of ATP which is then utilized by the different bodily processes like muscle contraction for movement, growth and repair of cells. Respiration involves the oxidation of organic compounds like glucose (breakdown of glucose using oxygen), hence producing carbon dioxide and water. Moreover, respiration has different stages, starting from glycolysis in the cytoplasm which is an active process, pyruvate oxidation, Krebs cycle, and oxidative phosphorylation in the mitochondria. Respiration is an involuntary procedure and happens automatically in the body, depending on the availability of the reactants.
There are two main types of respiration: aerobic and anaerobic respiration. Aerobic respiration occurs in the presence of oxygen, while the latter happens in the absence of oxygen due to which incomplete breakdown of glucose happens, and less amount of energy is released. Also, in humans, lactic acid is produced as the product of anaerobic respiration while in yeast ethanol and carbon dioxide is produced.