How Primary Structure Determines Protein Function
Proteins are everywhere. As enzymes, they catalyse chemical reactions. There are many different types of proteins: carrier and channel proteins which transport substances, receptor proteins which are recognition site for antibodies and hormones, structural proteins which support cells and tissues, and hormones which transmit information. Proteins are big molecules with large molecular masses that are made up of many amino acids; they’re, essentially, polymers of amino acids. There are only about 20 different types of amino acids but they make up millions of proteins. There are four elements that make up amino acids: carbon, oxygen, hydrogen and nitrogen. However, some amino acids such as cysteine also contain sulphur and phosphorous. All amino acids have the same basic structure: NH2CHOOHR, where NH2 is the amine group, COOH is the carboxyl group and R relates to the variable group, which differs from one amino acid to another. When two amino acid molecules bond, a peptide bond is formed; peptide bonds are created by enzyme catalysed condensation reactions and can only be broken by enzyme catalysed hydrolysis reactions. The breaking down of proteins in the body is very important. For example, in hormone regulation, cells that are targeted by hormones contain enzymes to break down those hormones. This stops the effects from being permanent and allows them to be controlled. Primary Structure
Most amino acids can be added to each other to form a polypeptide. Each amino acid that joins the chain is joined by a peptide bond. A polypeptide chain always has an amino group at one end of the molecule and a carboxyl group at the other end. A polypeptide chain contains hundreds of amino acids. When a polypeptide bonds with another, it forms a protein that contains thousands of amino acids. These proteins have a structure that consists of four different levels: primary structure, secondary structure, tertiary structure...
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