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what are the different types of haemoglobin and their functions?

Hemoglobin is present in red blood cells and is an essential chemical which carries oxygen from lungs to other parts of the body. It is metalloprotein having quarternary structure which contains iron and performs the important function of transporting oxygen via RBCs in blood in mammals as well as other animals. It also fulfills different effect modulation and gas transport duties, although which differ from species to species. Some oxygen is dissolved in blood while some bound to hemoglobin. But the more amount of oxygen molecules bounded to hemoglobin, the more oxygen in reached to every part of the body. Hence this pack of chemicals known as hemoglobin performs the most vital duty of binding oxygen to it so that it reaches each and every body part.
The name hemoglobin is made from the blend of heme and globin. Globin is the globular protein in which heme-an iron atom is embedded which is the main chemical binding oxygen. The common type of hemoglobin consists of four subunits:

    Two alpha (?) subunits or globins
    Two beta (?) subunits or globins

All these units are made up of long protein stretch which usually is coiled in the form of eight alpha helices. The heme group is a ring of carbon atoms having an iron atom embedded in the center. This iron atom is safely protected in the centre because this atom is capable of holding the oxygen by forming chemical bond. Iron ion binds to six different things whereas, the oxygen forms a coordinate covalent bond with it and gets released in blood at the right place. Iron is a transition metal having red color and  is the reasonfor the blood red colour.
 Functions:
The hemoglobin molecules with the help of external chemical factors take up oxygen molecules in the lungs and then send them to the various tissues of our body. The biggest regulator of oxygen affinity in the hemoglobin is the oxygen itself. (If in lungs, the oxygen levels are high the hemoglobin shows greater affinity towards the oxygen molecules and as it bounds to more oxygen, this property of affinity increases and vice versa. When the oxyhemoglobin binds to the maximum capacity, it becomes saturated but its affinity towards oxygen increases whereas when this binding loose oxygen molecule the affinity decreases.) This regulation activity is called as cooperativity and is an important function as it allows maximum amount of hemoglobin to be carried to the tissues and also allows deoxyhemoglobin which is releasing the oxygen tissue. The external chemical factors which help in regulation of oxyhemoglobin affinity includes pH, DPG (2, 3-diphosphoglycerate) and carbon dioxide.

 


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