breakdown of oxyhaemoglobin takes place in tissues or tissue capillaries. please explain properly

The capacity of hemoglobin to bind oxygen depends on the presence of a bound prosthetic group called heme. The heme group is responsible for the distinctive red color of blood. The heme group consists of an organic component and a central iron atom. The organic component, called protoporphyrin, is made up of four pyrrole rings linked by methene bridges to form a tetrapyrrole ring. Four methyl groups, two vinyl groups, and two propionate side chains are attached to it.

As stated above, protoporphyrin has got 4 pyrrole rings to which one molecule of oxygen combines.

*At the level of alveoli *-

When the partial of Oxygen is high, hemoglobin binds with Oxygen molecule leading to the formation of a compound called Oxyhaemoglobin. This effect is called as HALDANE'S EFFECT.

When the blood circulates and reaches the tissues,the tissues are site of active metabolism. Due to the result of respiratory processes,a high amount of Carbon Dioxide accumulates at the site.Here,the partial pressure of Carbon Dioxide becomes high which leads to dissociation of Oxyhaemoglobin.

At the tissue level,high amount of oxygen is required due to which Oxyhaemoglobin dissociates. Here,large amount of hydrogen ions and Carbon Dioxide is produced. Both these factors are responsible for the breaking of Oxyhaemoglobin(due to decrease in pH)

The regulation of oxygen binding by hydrogen ions and carbon dioxide is called the Bohr effect.