Three of the four classes of macromolecules—carbohydrates, proteins, and nucleic acids—form chainlike molecules called polymers. A polymer is a long molecule consisting of many similar or identical building blocks linked by covalent bonds. The repeated units are small molecules called monomers.
Tastes are detected on the tongue through cells called gustatory cells. Gustatory cells have a variety of taste receptors. When bitterness is detected, the brain receives a message from these cells.
