Why do sweeteners taste different to sugar?

Chris - We talked about Aspartame last week, and that's about 200 times sweeter than sugar. The reason that we use it, of course, is to make things taste much sweeter without having to add additional sugar - because the sweetener molecule has got virtually no calories in it compared to the large amount of calories that are in sugar. It fools the tongue into thinking things taste sweet because it locks on to the same chemical receptor - the docking station that recognizes sugar - making it taste sweet. In reality it doesn't actually impart any caloric contribution. The reason that it also has other tastes is because it doesn't just recognize the receptor for sugar, it also binds to other flavour receptors as well.