This story is a supplement to the feature "Magnifying Taste: New Chemicals Trick the Brain into Eating Less" which was printed in the August 2008 issue of Scientific American.

Contrary to old models (below left), the tongue does not have regions that detect one type of flavor. Instead taste buds embedded in papilla (bumps) across the tongue sense all flavors. Each bud contains elongated taste cells that respond to sweet, salty, sour, bitter or umami (savory). Receptors on the surface of a sweet cell, for example, bind to sugar molecules.

If only a few sugars are bound, the bud sends a weak signal to the brain (left); if more sugars are present, more binding will cause a stronger signal of “sweet”(middle). Taste enhancer molecules, which do not prompt a signal on their own, strengthen the likelihood that sugar molecules and receptors will bind, intensifying the sweet sensation even when only a few sugar molecules are present (right). —M.W.

Few sugar molecules present; weak taste

Many sugars present; strong taste

Few sugars plus enhancers; strong taste

Illustrations: Alice Y. Chen