Proteins are a diverse class of biochemical macromolecules, including substances as (apparently) unrelated as silk and sinew, hair and horn, feathers and flagella, enzymes and epidermis, gelatine (jelly) and gluten and gore, spider web, meat and fish muscle. Yet they are unified by being polymers of amino acids. Discovery of the nature of proteins is presented as a classroom exercise, leading to knowledge about the many ways proteins affect us. A simple laboratory experiment demonstrates protein isolation from a wheat-flour dough. The exercise is relevant to the broad range of science-based subjects and can be adapted to any high-school level. (Contains 4 figures and 1 photo.)