Hemoglobin – Functions, Structure, Mutations

Hemoglobin which is sometimes abbreviated as Hb or Hgb, is the iron-containing oxygen-transport component of the Red Blood Cells or RBCs of all vertebrates. Hemoglobin a type of metalloprotein carries oxygen from the respiratory organs (lungs) to the rest of the body (i.e., the tissues) where it releases the oxygen. This oxygen is then used to burn nutrients to provide energy to power the functions of the organism. Later it collects the resultant carbon dioxide to bring it back to the respiratory organs to be released out from the organism.

Functions of Hemoglobin

  • Carry oxygen
  • Carry Carbon Dioxide
  • Carry Nitric Oxide

Hemoglobin has an oxygen binding capacity and on average hemoglobin molecule can bind (carry) up to four oxygen molecules. Sometimes Hemoglobin is involved in the transport of other gases: it carries some of the body’s respiratory carbon dioxide as carbaminohemoglobin, in which CO2 is bound to the globin protein. The molecule also carries the important regulatory molecule nitric oxide bound to a globin protein thiol group, releasing it at the same time as oxygen.

Structure of Hemoglobin

  • Hemoglobin is made of protein
  • Protein is made of amino acid or polypeptide
  • Polypeptide sequence depends on DNA

Hemoglobin is primarily made of protein or the “globin” chain. These proteins are folded chains of a large number of different amino acids called polypeptides. The sequence of this polypeptide is determined by the stretches of DNA called genes.

Mutations of hemoglobin

  • Sickle Cell diseases
  • Thalassemias

Mutations in the genes for the hemoglobin protein may result in hemoglobin variants, however many of these mutant forms of hemoglobin cause no disease. But some of these mutant forms of hemoglobin do result in a group of hereditary diseases termed the hemoglobinopathies. The best known hemoglobinopathy is sickle-cell disease, which was the first human disease whose mechanism was understood at the molecular level. Another set of disease called thalassemia is also a result of underproduction of normal and sometimes abnormal hemoglobins. All these diseases produce anemia.