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.
For instance, the blood protein hemogobin is made up of four polypeptide chains, each of which also contains a heme molecule, which is ring structure with an iron atom in its center. Proteins have different shapes and molecular weights, depending on the amino acid sequence. For example, hemoglobin is a globular protein, which means it folds into a compact globe-like structure, but collagen, found in our skin, is a fibrous protein, which means it folds into a long extended fiber-like chain.