Since amino acids have both a carboxylic acid group which tends to give up a hydrogen ion and an imino which tends to take up a hydrogen ion, they can end up with both a negative charge on the carboxyl group and a positive charge on the imino group. ThatвЂ™s why glycine is not optically active and it does not rotate the plane of polarized light. It has a carboxyl group, an amino group, a hydrogen and another hydrogen atom. So, glycineвЂ™s alpha carbon does not have four different things bonded to it. In the Glycine molecule, the side chain is just another hydrogen atom. This means the molecule is chiral which means that it would be optically active and it will rotate the plane of polarized light. The carboxyl group, an amino group, a hydrogen and a side chain. In other words, the alpha carbon has four different things bonded to it. In most alpha amino acids, the alpha carbon is a chiral center. So, proline is an exception to that rule. That is because its amino group is attached not only to the alpha carbon but also to another carbon to form a ring called an imino ring. The amino acid proline is not considered an alpha amino acid. This means that most biologically significant amino acids are alpha amino acids. When you look at an amino acid, youвЂ™ll see that the carboxylic acid group and the NH3 group are attached to a carbon atom called the alpha carbon. glycine, alanine, valine, leucine, isoleucine, phenylalanine, methionine, aspartic acid, asparagine, glutamic acid, glutamine, lysine, arginine, histidine, serine, threonine, tyrosine, tryptophan, cysteine, and proline. So, listen to these names but donвЂ™t try to memorize them. You should be somewhat familiar with them.

There are about 20 different amino acids that are important in building proteins. To do that, we would have to put in a molecule of water. Now if we started with a protein and wanted to get amino acids out of it, we have to break the peptide bonds. We said that each peptide bond involves the removal of one molecule of water. Amino acids can link together with peptide bonds to form very long chains called polypeptide chains or proteins. The link between two amino acids is called a peptide bond. They do this by linking the carboxyl carbon of one amino acid to the nitrogen of another and in the process a molecule of water is lost. You need to know how two amino acids link themselves together. A protein is a chain of amino acids linked together. An amino acid is basically a carboxylic acid with an amino group attached somewhere on the carbon chain.ДЄmino acids are important because they form proteins. Another important derivative of ammonia is the amino acid.

Mcat list of hydrophobic amino acids