Put simply, a carbohydrate is a compound consisting only of carbon, hydrogen, and oxygen. \u00a0The ratio between the three is roughly 1:2:1. \u00a0“Hydrate” suggests water (H2<\/sub>O): note that in carbohydrates, the same 2:1 ratio exists between hydrogen and oxygen. Sugar, starch, and glycogen are all carbohydrates.<\/p>\n In biology 12, sugars are either monosaccharides or disaccharides. \u00a0A monosaccharide is a simple sugar. Technically, it can have three to seven carbon atoms. \u00a0However, in Bi-12, we mainly think of glucose (6 carbons), fructose (6 C), galactose (found in milk, 6 C as well), or ribose (5 C). \u00a0All are single-ring structures.<\/p>\n A disaccharide is two monosaccharides fused together; hence, it’s a two-ring structure. Sucrose is an example: \u00a0it comes from the union of glucose and fructose. \u00a0Bond two glucoses together and you get maltose. Lactose is glucose plus galactose.<\/p>\n If you bond many monosaccharides together, you get a polysaccharide. \u00a0Three instances of polysaccharides are starch, glycogen, and cellulose. \u00a0All are polymers of glucose molecules – meaning that they consist of large numbers of glucose molecules strung together. \u00a0(Glucose is the monomer, whereas starch, for example, is the polymer.) \u00a0Starch is the molecule that plants use to store glucose; glycogen is what animals use. \u00a0In cellulose, the glucose molecules are joined so as to be indigestible; cellulose gives plants their erect, rigid structure.<\/p>\n There’s the “skinny” on carbohydrates:)<\/p>\n Sources:<\/p>\n Inquiry into Life<\/em>, Eleventh Edition, by Sylvia S. Mader. \u00a0McGraw-Hill: 2006.<\/p>\n Biology 12, Module I: Cell Biology I<\/em>. \u00a0Open School BC: 2007.<\/p>\n