The protein we chose to look at was insulin.  Insulin is a signalling hormone that indicates levels of sugar in the blood.  It is synthesized in the pancreas, and the distributed through the body to have an effect on  many systems.  Insulin is a relatively small molecule, measuring aproximately 25x16x18 angstroms.  As such, cells actually synthesized as a larger molecule, and 2 chains are cut off.  Insulin is a great molecule to use to study protein structure, because it has multiple chains held together by disulfide bonds.  This image shows an insulin monomer, the A and B chains are in different colors, and the three disulfide bonds are shown with yellow sticks.