Final answer:
Amino acids have both amine and carboxyl groups, enabling them to form peptide bonds and function as buffers. The distinct side chains of amino acids determine their properties and how they interact within proteins.
Step-by-step explanation:
Amino acids are fundamental building blocks of proteins, characterized by the presence of both an amine group (-NH2) and a carboxyl group (-COOH) attached to the same carbon atom, known as the alpha (a) carbon. They are unique because they can exist in a form known as a zwitterion, which has separate positive (amine group) and negative (carboxyl group) charges. One of the critical reactions involving amino acids is the formation of peptide bonds, where the amine group of one amino acid reacts with the carboxyl group of another, releasing a molecule of water and creating an amide linkage. This process is essential for building the polypeptide chains that form proteins.
Amino acids also serve as buffers in biological systems, helping to maintain the acid-base balance in the body. Each of the 20 common amino acids has a distinctive side chain, or R group, which defines its properties and how it interacts with other amino acids within a protein structure. These R groups can vary in size, polarity, and composition, such as in the sulfur-containing side chains of cysteine and methionine, which influence the properties of the proteins they are part of.