Proteins are large, complex molecules made up of long chains of amino acids. They perform a vast array of functions in cells, including:

* Enzymes: Catalyze biochemical reactions

* Structural components: Provide support and shape to cells and tissues

* Hormones: Act as chemical messengers

* Antibodies: Defend the body against infection

* Transport proteins: Carry molecules across cell membranes

* Contractile proteins: Enable muscle movement