The name carbohydrate comes from the dark days of science when all they knew was that the chemical formula added up to the same number of H20s as Cs, thus a "Hydrated" Carbon. Actually, a carbohydrate is one or more sugars in a chain. The simplest sugar, a monosaccharide is a circle of carbons with hydroxy (-OH) groups attached to each carbon. Most of the sugars in our foods are hexoses (six carbon) sugars. Glucose and galactose are hexoses and very easily broken down by the glycolytic enzymes in our body. The next level is a disaccharide, two sugars. Glucose+galactose is sucrose (I think, I don't have any reference books in front of me.) Lactose and Fructose are also disaccharides and your body must use a special enzyme to break the bond between the two sugar rings before the free monosaccharides can enter the glycolytic pathway in the body. (Imagine a chain of two rings, each ring being made up of six beads. In order to get the beads, you have to separate the links, then take the beads apart one by one.) Starches have dozens of sugar units and enzymes are required to break these chains down into individual sugar links. Breads, grains, pasta, rice, all have starches in them that can be broken down by human beings into the component sugars and digested. Yet another type of carbohydrate is cellulose--a plant polysaccharide. We can't break cellulose down into simple sugars because we lack the enzyme to break the bonds between the sugars. The monosaccharides in starch are connected by a different bond than the monosaccharides in cellulose, thus, the cellulose passes through our system essentially unchanged. Cows culture microorganisms in their guts that break up the cellulose for them so they can get the simple sugars out of it. However, when we eat celery, we get very few calories out of it. An enzyme is a special protein that does work for you in your body by catalyzine chemical reactions. What we can use for food an cannot is dictated by our enzymes, which differ from ferret enzymes and bacterial enzymes, etc. In sum, carbohydrates are all kinds of sugar, from the very simplest, to the long, complex chains of sugars which we call "fiber." -Catherine the off-topic biochemist [Posted in FML issue 1911]