Proteins
Proteins are the cell's 'workers'. You have many thousands of different proteins in your body. Some are used as building blocks: your hair and nails contain the protein keratin, while your muscles contain actin and myosin. Other kinds of proteins carry oxygen around your body, fight infections and detect the light entering your eyes. A vital group of proteins - enzymes - controls the rate of the chemical reactions in your body that make all the other molecules you need.
