Polymers are the most important molecules in living systems.
Proteins function in many ways. But perhaps their most important role is to orchestrate the thousands of chemical reactions that are going on in cells. Enzyme can distinguish among many different compounds, and bind only to certain ones. This specific binding arises from the fact that the proteins have pockets on their surface into which only complementary substances fit. To form these complementary pockets, proteins have to assume a highly convoluted shape.