Proteins, together with carbohydrates and fats, are one of the three major nutrients. Proteins are an important component making up our body's organs and muscle as well as hormones and enzymes. Proteins make up about 20% of our bodies. 500 amino acids have been discovered in the natural world. However, different arrangements of just 20 of these amino acids make hundreds of thousands of types of proteins.
In 1953, the English biochemist Frederick Sanger studied the pancreas of a cow and found and sequenced insulin (a hormone, made of 51 amino acids, that our bodies use to process sugar). Different animals, such as cows, pigs and sheep also have insulin in their bodies. Their insulin is also made up of the same 51 amino acids, but in different sequences.