Hemoglobin is a spherical molecule. It is composed of iron called heme and protein called globin. 100 cc of blood contains 15.8 grams of hemoglobin in men and 13.7 grams in women. Heme and globin ratio in hemoglobin is 1:25. 33.33% of Heme is iron. Adult human blood contains only 4-5 grams of iron. Its chemical symbol is (C712H1130O245N214S2Fe)4 and molecular weight is 64,450 daltons. Heme is ferrous iron and globin is a polypeptide protein. Each hemoglobin contains 4 heme and 4 globin proteins. Hence it is written as Hb4.