Question 9
Antibodies, hormones such as insulin, and enzymes are all made of what?
The right answer is the one marked above.
All three are made of protein. It is the most versatile of the biological molecules.
Protein also builds the cell membrane, forms collagen in connective tissue and keratin in hair and feathers, and can even be broken down for energy — though only when carbohydrate and fat are not supplying enough.