Which insulin source is derived from animals and resembles human insulin, historically used before synthetic forms?

• A. Porcine insulin
• B. Human insulin
• C. Recombinant insulin
• D. Bovine insulin

Answer: (A)

The main idea is understanding where insulin used to come from before modern synthetic forms and which animal source most closely resembled human insulin. Porcine insulin, derived from pig pancreas, is structurally very similar to human insulin, differing by only a single amino acid. That close likeness made its biological action and potency resemble human insulin closely, and it tended to provoke fewer immune reactions than other animal sources. Because of this compatibility, porcine insulin was widely used historically before recombinant, genetically engineered insulin became available. Recombinant insulin is produced in microorganisms and is identical to human insulin, eliminating the need for animal-derived sources. Bovine insulin is also animal-derived but differs a bit more from human insulin, so porcine insulin was preferred when an animal-based option was used.