How does gaseous exchange take place at blood level ?

Explanation

(1)The relative amount of gases and their combining capacity with haemoglobin and other substances in blood determine their transport via blood in the body.
(2)When oxygen present in the air is within normal limits , almost all of it is carried in the blood by binding to haemoglobin.
(3) Haemoglobin, a protein which has iron , is present in red blood cells .
(4)When oxygen is diffused in the blood , it quickly combines with the haemoglobin to form oxyhaemoglobin.
`Hb + 4O_2 to underset"(Oxyhaemoglobin)"(Hb(O_2)_4)` (in lungs)
(5)Haemoglobin in reverse , can also happen to yield a molecule of haemoglobin and oxygen.
`Hb(O_2)_4 to Hb + 4O_2` ( in tissues )
(6)Carbon dioxide is usually transported as carbonate. Some amount of `CO_2` is combines with haemoglobin and rest is dissolved in blood plasma.