Proteins are specific types of amides and are made in living systems at low temperatures using enzymes. Low molecular weight proteins, referred to as polypeptides, can also be man-made. An amide is a compound conforming to the structure in Figure 1.
Amides are made by the reaction of an acid, ester or triglyceride with an amine. Alkanolamides are used to shift the salt curve in shampoos, allowing for a higher viscosity with less salt necessary to modify the bubble structure. A specific example of a reaction is MEA alkanolamide (Figure 2).
A protein is a polyamide compound, generally natural, made by reacting amino acids. Amino acids contain both an amino group and a carboxyl group in the same molecule. An example is glycine (Figure 3).
Proteins are special types of amides and the bonds in them are referred to as peptide bonds. The amino group reacts with the carboxyl group, releasing water and creating a polypeptide. As more and more amino acids are added to the chain, a protein results (Figure 4).