Types of hemoglobin

Hemoglobin is an oxygen carrying pigment which is composed of a protein and prosthetic group.

The protein part of hemoglobin is a globin protein, which is made up of four chains.Two of them are alpha chains but the other two may be beta, gamma, delta or epsilon depending on the types of hemoglobin.

Hemoglobin is one of the most important molecule of life because it is associated with the transfer of oxygen.Abnormality in its structure leads to various disorders and diseases.

It has various types.All of them have its own role in different periods of life.Like feotal hemoglobin is the only oxygen carrying molecule in fetus while hemoglobin A is the major hemoglobin after birth.

Functions of hemoglobin:

Hemoglobin has various functions and different types have different functions, which are discussed later.Here are all of the functions of hemoglobin:

• First of all hemoglobin helps in the transport of oxygen.
• Hemoglobin keeps the pH in narrow range by its buffer action.
• The red color of the blood is due to hemoglobin.
• Glycosylated hemoglobin attaches sugar which can be used to determine sugar level of past.
• It is a modulator of erythrocyte metabolism.
• It is a molecular heat transducer because of its oxygenation and De-oxygenation cycle in the body.

Read about structure and functions of hemoglobin in detail.

Classification of hemoglobin:

Normal haemoglobin is of various types depending on its function and the age of human.Like in fetus it is called foetal hemoglobin while after birth it is called Hemoglobin A.Here is the list of all normal hemoglobin:

• Hemoglobin A1 (Hb-A1)
• Foetal hemoglobin (Hb-f)
• Hemoglobin A2 (Hb-A2)
• Embryonic hemoglobin
• Hemoglobin A3 (Hb-A3)
• Gycosylated hemoglobin (Hb-A1c)

Now all the types of hemoglobin are discussed one by one:

Varieties of hemoglobin in normal human:

Here is a list of hemoglobin types that are normally present in human blood:

Hemoglobin A1:

Hemoglobin A1 (Hb-A1) among the normal hemoglobin is found in the largest amount in human after birth.It is not produced till birth instead, another hemoglobin called foetal hemoglobin is present which is described later.

Hb A1 is made up of two alpha and two beta chains.It is present 90-95 percent in adult human while in new born babies its amount is usually about 85 percent and before birth, it is absent.

Foetal hemoglobin (Hb-f):

It is called feotal hemoglobin because it is present is fetus.It is made up of two alpha and two gamma chains.It is only hemoglobin in fetus, while after birth it is reduced to 15 percent, while after some days of birth it is reduced to 2-3 percent and in adult it is present 2-3 percent in blood.

Here are the differences between hemoglobin A1 and feotal hemoglobin.

Hemoglobin A2:

It is present in less amount in adults.Usually about 2.5 percent.It is made up of two alpha and two delta chains.

Embryonic hemoglobin:

It is present in up to three months intrauterine life.It is present in embryo and is made up of two alpha and two epsilon chains.After three months of intrauterine life it is replaced by foetal  hemoglobin.

Hemoglobin A3:

It is the altered form of hemoglobin A and is chiefly found in old red blood cells.It is present between 3 to 10 of the total hemoglobin in body.

Glycosylated hemoglobin Or Hb-A1c:

It is also present in minor quantity in normal human adult about 3-5 percent.It is important for the diagnosis of diabetes and is present 6 to 15 percent in diabetic patient.

Importance:

Sugar can attach to glycosylated hemoglobin due to presence of valine.Therefore the past history of diabetic patient can be easily calculated from this hemoglobin