Although Dr. Krebs’s research on protein metabolism was important, he is best known for his discovery of the cellular reactions involving the substances formed from the breakdown of carbohydrates, fats, and proteins in the body. Specifically, in 1937, Dr. Krebs discovered the existence of a cycle of chemical reactions that combines the end product of carbohydrate breakdown (this product was later named acetyl-CoA) with oxaloacetic acid to from citric acid.