Hemoglobin Structure

Features

• Hemoglobin A, the most commonly occurring type of hemoglobin in adult humans, consists of four globular protein subunits. These are arranged as two alpha (α) and two beta (β) subunits to form what is known as a tetramer.
  
  

Function

• Each hemoglobin subunit contains an embedded heme group. This consists of an atom of the metallic element iron, held in a flat organic (carbon) ring structure, known as a porphyrin. It is the iron atom to which oxygen binds to allow hemoglobin to perform is oxygen transport function.
  
  

Types

• The structure of the hemoglobin molecule allows oxygen molecules to bind reversibly to it. However, certain other molecules, including carbon monoxide, bind irreversibly to hemoglobin, preventing oxygen transport and causing death by asphyxiation.