I came across this today in my chemistry book, and as someone who really likes tasting things, I found this really interesting. The reason some artificial sugars are calorie-free is because our cells don't metabolize them (metabolize is a word we use all the time when talking about diet but I've learned that it really just means chemical reactions happening in cells). They just pass through our bodies unchanged. Sugar, however, is used by our bodies and is metabolized by oxygen to produce energy, CO2, and H20.
But taste is independent of metabolism. Our taste buds or taste receptor proteins have a little space where a food molecule can fit in snugly. When a sugar shaped molecule fits into the sugar receptor protein, the protein splits apart and causes a series of events that result in a nerve signals that tell the brain that you are tasting something sweet.
But what I found to be really interesting is that artificial sugars taste sweet simply because they fit into these receptor proteins. These molecules are similar enough in shape that they taste almost the same. We just metabolize them differently or not at all.
