IB Biology B1.2 Notes

The next molecular group to cover is proteins. Proteins are a group of molecules composed of carbon, hydrogen, oxygen, nitrogen, and sometime sulfur. For the SL curriculum, you are expected to only understand it has three levels of structure: amino acids, dipeptides, and polypeptides.

It is easier to think of these levels in comparison to carbohydrates. Just as monosaccharides are the monomers of carbohydrates, amino acids are the monomers of proteins. There are twenty different amino acids, each containing a central carbon bonded to an NH₂ (amine) group, a COOH (carboxyl) group, a hydrogen, and an R-group. The R-group is variable, meaning it could be anything from just a hydrogen to a complex side group, and its structure determines the type of amino acid formed.