Hemoglobin is a main component in mammalian blood. Although it does not have an exact molecular formula, all hemoglobins can be represented by the empirical formula C₇₃₈H₁₁₆₆N₈₁₂O_{203_S2}Fe. Hemoglobin is more accurately described by the series of amino acids that create it. In the case of hemoglobin, each amino acid has an Fe ion at its core.