Proteins consist of one or more long chains of amino acids that fold up into a specific arrangement, and each is presumably capable of some kind of biological function (though we don’t know for sure that every protein has a biological function—the function of each protein is one thing many biochemists are still working hard to figure out). Some proteins act to protect an organism from invading pathogens, some help to carry messages between different areas of the body, some are responsible for movement of muscles, and some provide structural support for cells. Many proteins also fall into a class called enzymes, which is a name for proteins that catalyze specific chemical reactions in biological systems.