* Proteins: Proteins are made up of long chains of amino acids linked together. This is their primary function.

* Enzymes: Enzymes are proteins that catalyze (speed up) biochemical reactions.

* Hormones: Some hormones, such as insulin and growth hormone, are proteins.

* Antibodies: Antibodies are proteins that help the immune system fight off infections.

Let me know if you'd like more detail on any of these!