haemoglobin/A loose connective tissue

          HAEMOGLOBIN(A LOOSE CONNECTIVE TISSUE)

haemoglobin is the iron containing protein present in red blood cell of all living organism(especially in vertebrates).haemoglobin is red colored pigment which is due to heme(a component of hemoglobin structure)
haemoglobin is made up of two subunits( HEME+GLOBIN). Heme is iron containing pigment part and Globin is protein part of HEMOGLOBIN molecule.
the main function of haemoglobin is to  carries oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs.It also functions as a buffer in the regulation of acid base balance.
A haemoglobin is a  complex substance consisting of  protein and pigment part heme and a protein, globin.The protein portion of each of these chains is called globulin. The globin parts has two chains parts a and b globin chains and they are very similar in structure. The globulin is a conjugated protein and heme contains iron in ferrous state.Haemoglobin contains four polypeptide chains namely two alpha and two beta chains. Each of the four chains unites with a heme group resulting in a haemoglobin molecule. 

SYNTHESIS OF HAEMOGLOBIN MOLECULE:

Haemoglobin (Hb) is synthesized by many series of steps.
 globulin protein parts are synthesized by ribosomes(present in cell cytoplasmor a cell organelle) and the heme part is synthesized in the mitochondria of cell.

FORMATION:

formation of Hb(inside RBC) continues in the cell throughout its early development from the erythroblast,pro-erythroblast to the reticulocyte in the stem cell(continue dividing cell).the site of production of RBC is vary from stage to stage of life like in embryo stage bone marrow,liver is the main site of haemoglobin synthesis then after birth long bones took their duty. in reticulocyte stage, the nucleus is lost in mammalian red blood cells(, but not in birds and many other species. the main purpose of nucleus disintegration is too increase the amount of oxygen carry capacity of RBC, that is why RBC called as enucleated cell(loss of nucleus during it's development)

FACTOR AFFECTING HEMOGLOBIN SYNTHESIS:

The amount of Hb in the blood is influenced by: 

1. Age:Haemoglobin content in young one is high,because of requirement of high nutrition and oxygen to actively dividing cell of body to maintain growth and production, then old one.
   
2.   muscular activity: increase in muscle tension increase oxygen and nutrition uptake, for the good amount of supply, body form high amount of RBC .
   
3.  season: season affect RBC synthesis in term of heat exchange,in cold weather body loose their heat more than hot weather.
   
4. altitude: in high altitude oxygen level is low,to maintain body oxygen level RBC content is increased by multiple fold.
   
5. trauma: any trauma or injury to body lead to loss of blood from body and RBC content of body decline.
   
6. Erythropoietin Hormone: stimulate RBC production by stimulating stem cell of body(bone marow cell)
   
   
   

Types of  hemoglobin :

Based on physiology, the hemoglobins are 2 type, adult hemoglobin and fetal hemoglobin.the Hb are also classified as HbA, HbB, HbC and HbF. Human beings show three types of Hb, HbA (98%), HbA₂ (2%) in the adult and HbF in fetus and new born. HbF has higher affinity for O₂. In human and animal fetal hemoglobin (HbF) is replaced by the adult types with in 4 to 8 weeks after birth. 
 HbS is responsible for sickle-cell anaemia in some race. HbC and HbE cause failure of synthesis of alpha or beta chains thus results in alpha or beta thalassemia.

DERIVATIVE OF HEMOGLOBIN:

• Oxyhemoglobin:

hemoglobin has an important relationship with oxygen. Oxygen forms reversible combination with hemoglobin called oxy-Hb, when RBC passing through lungs, since there are four ferrous atoms in the hemoglobin molecule,and four molecules of oxygen are transported by a molecule of hemoglobin.As blood is transported through the systemic circulation hemoglobin loses its oxygen to the tissues.The oxygen carrying capacity of the hemoglobin is dependent on the pigment it contains which in turn depends on the iron content for oxygen combining capacity.

• Myoglobin:

It is a true hemoglobin and functions to store oxygen in the muscle. It contains only one heme and a polypeptide chain. It contains only one iron atom and can therefore store only one molecule of O_2.

• Carboxyhemoglobin

Hb has 200 times more affinity for carbon monoxide than oxygen.

• Methemoglobin 

It is formed by the oxidation of ferrous iron to ferric iron. During the circulation of blood methemoglobin is formed by the oxidation of ferrous iron to ferric iron. Ferrihemoglobin cannot combine with oxygen, hence is useless as a respiratory pigment in the blood. It produces dark colored blood.