Hemoglobin is made up of small molecules called amino acids. Each hemoglobin molecule is made up of four heme groups surrounding a globin group, forming a tetrahedral structure. All hemoglobins carry the same prosthetic heme group iron protoporphyrin IX associated with a polypeptide chain of 141 (α) and 146 (β) amino acid residues. The porphyrin ring is wedged into its pocket by a phenylalanine of its polypeptide chain.
The heme part is synthesized in a series of steps in the in a series of steps in the mitochondria and the cytosol of immature red blood cells, while the globin protein parts are synthesized by ribosomes in the cytosol.
Hemoglobin increases O2 solubility in blood by about a hundredfold. This means that without hemoglobin, in order to provide sufficient oxygen to the tissues, blood would have to make a complete circuit through the body in less than a second, instead of the minute that it actually takes. Iron must be in ferrous state which can binds to oxygen and form oxy hemoglobin.
Hemoglobin picks up oxygen in the lungs, circulates through the bloodstream to the muscles (and other tissues), and drops off oxygen there. Myoglobin picks up the oxygen and delivers it to the mitochondria, where it is used to oxidize fuel molecules.
Hemoglobin in blood system
