What are oligosaccharides and starches?
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Monosaccharides not only serve as building blocks for disaccharides but also for some larger forms of carbohydrates as well. The most recognizable larger carbohydrate is starch. Starch is found in varying degrees in plants and their products (e.g. legumes, vegetables, fruits and grains). It consists of large straight and branching chains of the monosaccharide glucose (see Glycogen Figure). |
Some shorter, branching chains of glucose can be found as well, and foods and food manufactures will also use these in the production of foods. The short, branching chains used by food manufacturers are often called maltodextrins and is typically derived from the partial digestion of corn starch.
In the human diet, we can also find a small amount of carbohydrates, called oligosaccharides, constructed from just a few monosaccharides (three to ten) linked together. Since these are found in relatively small amounts, they are not as essential to discuss. However, a few of these carbohydrates (e.g., raffinose and stachyose) will require mention later on, not only for their nutritional value but for their effects within the digestive tract.
Plants make starch to store energy kind of like mammals store fat. Plant fibers, on the other hand, are not necessarily stored energy but serve more structural roles for plants. Like starch, fiber is composed of straight and branching chains of monosaccharides, but their monosaccharides building block are not limited only to glucose.
What do carbohydrates do in our body?
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Carbohydrates play quite a few roles in the human body, but perhaps none as important as being an energy source for all cells. All cells in the body will use glucose to some degree. Meanwhile, cells of the central nervous system as well as red blood cells and certain other types of cells will exclusively use glucose under normal situations. Carbohydrates also provide limited yet readily available energy store called glycogen. As an energy source, carbohydrate provides 4 calories per gram. Carbohydrates are also a modest yet vital component of cell membranes. Certain carbohydrates are also key portions of indispensable molecules. For example, molecules such as DNA and RNA contain the carbohydrate ribose. Ribose is a monosaccharide that can be made in our cells from glucose. Also, very complex carbohydrates called glycosaminoglycans (GAGs) are important in connective tissue, such as in our joints. The GAGs include chondroitin sulfate and hyaluronic acid, which are popular nutrition supplements for joint inflammatory disorders. |
