Artificial Sweeteners Fooled by Molecular Shape

Artificial sweeteners, such as aspartame (NutraSweet), taste sweet but have few or no calories. Why Because taste and caloric value are independent properties of foods. The caloric value of a food depends on the amount of energy released when the food is metabolized. For example, sucrose (table sugar) is metabohzed by oxidation to carbon dioxide and water  

When your body metabohzes a mole of sucrose, it obtains 5644 kJ of energy. Some artificial sweeteners, such as saccharin, for example, are not metabolized at all they just 

Chapter 10 Chemical Bonding II Molecular Shapes, Valence Bond Theory, and Molecular Orbital Theory 

The taste of a food, however, is independent of its metabolism. The sensation of taste originates in the tongne, where specialized taste cells act as highly sensitive and specific molecular detectors. These cells can discern sugar molecules from the thousands of different types of molecnles present in a mouthful of food. The main factors for this discrimination are the sngar molecnle s shape and charge distribution. 

The lock-and-key fit between the active site of a protein and a particular molecule is important not only to taste but to many other biological functions as well. Immune response, the sense of smell, and many types of drug action all depend on shape-specific interactions between molecules and proteins. In fact, our ability to determine the shapes of key biological molecules is largely responsible for the revolution in biology that has occurred over the last 50 years. 

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