Macromolecules Essay

The Different Roles of Macromolecules in Biology.There are four types of macromolecules that I am going to describe: Proteins, carbohydrates, lipids and nucleic acid. I will also describe the functions and why they are important in our bodies. Proteins Proteins are polymers of amino acids that are joined head-to-tail in a long chain that is then folded into a three-dimensional structure unique to each type of protein. The covalent linkage between two adjacent amino acids in a protein (or polypeptide) chain is called a peptide bond. There are twenty amino acids that make up proteins. Each amino acid has a typical generic structure as depicted in the diagram 1, the only variance in each amino acid lies in a unique side chain (R group). Most of the amino acids have a carboxyl group and an amino group as shown above. At physiological pH the natural amino acids exist as zwitterions, with a negatively charged carboxyl group and a positively charged amino group. The side chains vary greatly in their complexity and properties. Amino acids are classified by the chemical nature of their side chains. Five of the 20 amino acids have side chains that can form ions in solution and thereby can carry a charge. The others are uncharged: some are polar and hydrophilic and some are non-polar and hydrophobic. Proteins are not linear molecules as suggested when we write out a "string" of amino acid sequence, etc., for example. Rather, this "string" folds into an intricate three-dimensional structure that is unique to each protein. It is this three-dimensional structure that allows proteins to function. Thus in order to understand the details of protein function, one must understand protein structure. Protein structure is broken down into four levels. Primary structure refers to the "linear" sequence of amino acids. Proteins are large polypeptides of defined amino acid sequence (diagram 2). The sequence of amino acids in each protein is determined by the gene that encodes it. The gene