The fire emoji next to a friend's name means that you and that special, special person in your life have snapped one another within 24 hours for at least two days in a row. You know, like your friendship is on fire? Or...
In adult humans, the most common hemoglobin type is a tetramer (which contains 4 subunit proteins) called hemoglobin A, consisting of two Î± and two Î² subunits non-covalently bound, each made of 141 and 146 amino acid residues, respectively. This is denoted as Î± 2 Î² 2.
At its simplest level, hemoglobin is made up of amino acids stuck together in chains. These chains are polypeptides that are also stuck to a heme molecule, which is where the oxygen will eventually stick. Hemoglobin is different than other proteins because its individual polypeptides, of which there are four, are called globins instead of simply protein subunits.