Human insulin is a peptide hormone composed of 51 amino acids and has a molecular weight of 5808 Da. The islets of Langerhans in the pancreas produces insulin. The name comes from the Latin "insula" for "island". Insulin's structure varies slightly between species of animals. Insulin from different animal sources has different effects on the human carbohydrate metabolism process. Porcine insulin is especially close to the human version. So, people with diabetes can take in insulin extracted from pigs instead of producing their own insulin.