Proteins embedded in the plasma membrane have varied enzymatic and transport functions. Polarity of the peptide bond permits hydrogen bonding between parts of a polypeptide. Amino acids differ in nature of R group, ranging from single hydrogen to complicated ring compounds. There are 20 different amino acids commonly found in cells. A peptide is two or more amino acids joined together.
Polypeptides are chains of many amino acids joined by peptide bonds.
Both temperature and pH can change polypeptide shape. When such proteins lose their normal configuration, the protein is denatured. Once a protein loses its normal shape, it cannot perform its usual function. The sequence of amino acids, therefore, forecasts the protein's final shape. Final 3-D shape of a protein determines function of the protein in the organism.