We have IGD we have IGA IgM IgG and we have Ige And each one of these five different types of antibodies carry out a different type of mechanism. They function in a slightly different way to basically carry out the function of defending our human cells, our body cells, from these pathogenic invasions. Now, what about the structure of these antibodies? So antibodies consist of four polypeptide subunits that basically bind together via disulfide bridges, disulfide bonds which are covalent bonds between sulfur atoms. And they bind in such a way to form a Y shaped structure as shown in the following diagram. Now, two of these polypeptides are heavy chains.