Model rendering

We will start studying the most simple amino acid: glycine; this is the smallest amino acid, since its sidechain (R) is just a hydrogen atom. We can render the molecule in several styles:

• The model does not convey the real size and shape of the molecule, but allows to clearly perceive the different atoms and bonds.
• A model, or spheres, shows the size and shape the molecule really has, but makes it hard to assess the structure.
• In the model only the bonds are displayed. This model is adequate for studying the structure of large molecules.

In addition to glycine, in proteins there are other 19 kinds of amino acid, which differ on their sidechain. It is common to classify them according to the nature of that sidechain: aliphatic, aromatic, uncharged polar, positively or negatively charged.