General Discussion 

Hemoglobin (Hb) is a protein that can be found inside red blood cells, blood cells. Its main function is to transport oxygen from the lungs to the tissues of the human body and, at the same time, transport carbon dioxide from the tissues to the lungs, where it will be eliminated. 

You may have already asked why human blood is red. The explanation is precisely the presence of hemoglobin in red blood cells, which are also called red blood cells or erythrocytes.  

However, red blood is not common to all living beings. Some invertebrate animals, mainly crustaceans, have bluish blood due to the presence of the protein hemocyanin in the red blood cells.

The hemoglobin 

Hemoglobin, whose molecular formula is C2952H4464N3248O812S8Fe4 is a protein responsible for transporting oxygen in the human body. Its fibers measure about 7 to 8 μm and they are the main substance that stores the ferrous ion in our organism.

The word hemoglobin is related to its chemical structure: four globin chains (protein part) linked to a heme group (prosthetic group). The heme group has a ring structure (porphyrin), formed by four units associated with an iron ion (Fe2+). 

Globins can be of types "a" (alpha), "ß" (beta), "" (gamma), "d" (delta) and "e" (epsilon), but in adult humans only two of the alpha type and two beta type. In addition to the structural function, they make it possible to reverse the connection between iron and oxygen. 

Regarding its chemical and physical properties, the protein has molecular formula C2952H4664O832S8Fe4, pH 7, measures from 7 to 8 µm and in the blood it acquires a colloidal form, being found from 4.5 to 5.5 million/mm³.

Types of Hemoglobin 

• Hb A: consisting of two alpha and two beta chains, it is predominant in adults and represents 95% to 98% of total hemoglobin production; 

• Hb A2: composed of two alpha and two delta chains, it represents about 2% to 3% of total Hb in adults; 

• Hb F: consisting of two alpha and two gamma chains, being the main type of Hb produced by the fetus during pregnancy and reduced after birth. In adults, it accounts for only 2% of total hemoglobin. 

There are also some common hemoglobin variants: 

• Hb S: occurs in people with sickle cell anemia; 

• Hb C: causes hemolytic anemia and a small enlargement of the spleen; 

• Hb H: causes mild hemolytic anemia, microcytosis, and slight enlargement of the spleen.

Changes in Hemoglobin Levels 

Below are reference values ​​for the presence of Hb in the body, which can be verified through laboratory tests: 

• Newborns (full term): 13.5 to 19.6 (g/100ml) 

• Children (three months): 9.5 to 12.5 (g/100ml) 

• Children (one year): 11.0 to 13.00 (g/100ml) 

• Children (10 to 12 years): 11.5 to 14.8 (g/100ml) 

• Pregnant women: 11.5 to 16.00 (g/100ml) 

• Normal women: 12.00 to 16.5 (g/100ml) 

• Men: 13.5 to 18.00 (g/100ml)