Hemoglobin A

This is a conjugated protein, a red pigment whose molecular weight is 68,000. With a molecular formula of (C712H1130O245N214S2Fe) its content of iron is about 0.34%. hemoglobin forms crystal by cooling.

There are more than 30 abnormal hemogolobins. Hemoglobin readily combines with oxygen to form oxyhemoglobin and carbon monoxide to form carboxyhemoglobin, nitric oxide to form nitric oxide hemoglobin and with hydrogen sulphide to from sulphemoglobin. When exposed to air for long it forms methemoglobin.

It is responsible for carrying oxygen in blood and helps the oxygenation of tissues.

Hemoglobins stained red by eosin after formaldehyde fixation. Peroxidase methods are also available for demonstrating hemoglobin. Benzedine method can be used. In the Dunn-Thompson method for localizing hemoglobin, the end result is a greenish black final reaction product. Cholesterol demonstration can be performed by use of perchloric acid napthoquinone. In this reaction, perchloric acid forms insoluble perchlorate with cholester 3, 4 diene which then reacts with 1, 2 napthoqino: ne 4 sulphuric acid to form a blue pigment which must be examined immediately.

            Glycogen can be demonstrated in the RBC with the PAS method and the diastase digestion. Endogenous peroxidase can be demonstrated in RBC by the peroxidase antiperoxidase (PAP) reaction.

            Hemoglobin contained in the RBC consists of a haem (which is a porphyrin) and a protein, globin. There are 4 iron atoms in the centres of 4 protoporphyrin rings. The molecule of hemoglobin is spherical in shape, consisting of two polypeptide chains. The alpha carries 146. Its molecular weight is 66,000 daltons. The haem group of the hemoglobin has the ability to combine with oxygen as well as carbon dioxide and carbon monoxide.

            Several human disorders are recognized in which the hemoglobin molecule is abnormal.

Hemoglobin types

 

 

 

 

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