Hemoglobin is are ion component of red blood cell contain a protein that carried oxygen in the blood. The oxygen carried by hemoglobin is with help of hemoglobin circulated round the body system. The mechanism behind it is that Hemoglobin taken oxygen in the long when partial pressure of oxygen is high, and release the oxygen when the partial pressure is down or low. Each of the oxygen has a gram at which it combine with hemoglobin, each gram of hemoglobin combine with 1.34ml of oxygen. Tissue have lower partial pressure compare to blood cells, in such case, partial pressure in the blood cell has to be reduce to balance that of the tissue partial pressure. When it happen it result to the disassociation of oxygen carried by hemoglobin in the lung and release it to the plasma. The carbon dioxide is transfer from the lung in the mechanism. Carbon dioxide pressure from the tissue is on the high side, while that of the alveolar air of the lung is on the lower side. In a general note hemoglobin carried oxygen we breathe through the nose to the lung, from the lung and circulate it round the body system, and carry unwanted carbon dioxide by the body from the body to the lung and then expel through the nose. When this happen we said respiration has taken place.
Respiration can be define as the exchange of oxygen with carbon dioxide by the body system of animal it environment. In another way plant taken carbon dioxide and release oxygen to the environment of which the animal taken and release carbon dioxide to the environment. By looking at this we can see that and plant are contact exchange of the oxygen and carbon dioxide gas animals.