What is a protein?

A protein is a sequence of many amino acids. All proteins are made of amino acids. Humans have 20 distinguished amino acids that can arrange in thousands of different combinations and this means that they can create an incredibile variety of proteins. Proteins are made frome genes through the processes of transcription and translation which allow to transform a sequence of genes (DNA) in a sequence of amino acids. Proteins are complex structures. Amino acids are held together by peptide bonds, that link the carboxyl group of one amino acid (-COOH) to the amino group (NH3-) of the next one. This amino acid squence forms the primary structure of the protein. The sequence then folds and arranges in different shapes to give the secondary and tertiary structures. When peptide bonds form, a condensation reaction occurs and a molecule of H20 is produced. On the other hand, when peptide bonds are broken, an hydrolysis reaction occurs and amino acids take up one molecule of H2O to restore the carboxyl and amino groups.