In: Biology
**Biochemistry**
Clearly explain how the structure of hemoglobin is intricately connected to its function, using the principle listed below as the outline.
Every protein has its unique folding leads to make its unique 3D structure so that only specific ligand can pass through and reach to active domain or site and bind to catalytic site and form product.
Same things happens with hemoglobing where its structure uniquly attached with heme molecule which reside at centre of protein and surrounded by specific His amino acids located at very specific site which allow only its natural ligand O2 to pass while restrict CO, NO or CO2 which are inhibitor of hemoglobin.
Here CO, NO or CO2 are having high affinity for heme which is attached to hemoglobing but even then hemoglobin binds only to oxygen and the reason behind this is protein unique 3D structure in which Histidine located at 93rd position plays an important role as this distal His does not allow NO, CO and CO2 to pass inside to catalytic site while allow oxygen freely to pass and binds to catalytic site.
Another reason that proteins breathing concept which state that protein continous chnages its state after interecting with its ligand. If protein binds to its natural ligands then there is positive conformation change which allow next molecule of oxygen to bind much faster and easier which if CO/NO/CO2 is interecting with these amino acids then there is negative conformational changes and hence next molecule of CO/NO/CO2 does not binds as its binding affinity decreases.
Also Hemeglobin are 4 subunit protein 2 alpha dn 2 beta and all four can bind with oxygen. All subunit shows positive cooperation for binding with oxygen while negative cooperation with CO/NO/CO2.
hope its clear.. thanks