Amino Acids and Protein Background Info.
All amino acids have a simple chemical backbone with an amine group (the nitrogen containing part) at one end. At the other end is the acid part. This backbone is the same for all amino acids. The difference between them depends on a distinctive structure, the chemical side chain, that is attached to the backbone. It is the nature of the side chain that gives identity and chemical nature to each amino acid. Twenty amino acids with 20 different side chains make up the proteins of all living tissue.
The amino acids that make up proteins differ from fats and carbohydrates in that they contain the element nitrogen. Proteins differ from each other in the sequence of the amino acids that form a particular chain. They also differ in the way that the protein chain (also called a peptide chain) is linked, coiled, or twisted. (See AMINO ACIDS Transparencies #1 and #2 in Resources.)
Chemically, the backbone of every chain is -C-C-N-. This backbone is also called a peptide chain. If two amino acids join in a chain, it is called a dipeptide. A number of amino acids in a chain are called polypeptide. Molecules of water bind to both the backbone and polar groups of proteins. Polypeptide and proteins are formed from amino acids by a condensation reaction in which one amino acid loses -OH from -COOH and another loses -H from -NH2 to form a peptide bond. Repetition of this reaction (polymerization) converts dipeptide to polypeptide and these in turn to proteins. A strand formula for an amino acid, with the variable group R, has been used in the diagram. Breakdown of proteins to polypeptide to amino acids is the reverse process, an enzyme-catalyzed hydrolysis. (See POLYPEPTIDES AND PROTEINS transparency in Resources.)
There are 30 to several thousand amino acids contained in different proteins. All amino acids are similar in shape, but each one contains a unique side chain that allows formation of different...