GED Science Practice Test: Carbohydrates

Carbohydrates, as a group, include sugars, starches, and cellulose.  They are important to living things mainly as a source of energy.  Carbohydrates, or “carbs,” as they are colloquially called, can be found in cookies, chips, bread, and other substances that you think of that contain sugars or starches.  Cellulose is a carbohydrate that is not digested by humans, but can be used metabolically by other mammals.  Animals can store carbohydrates in the liver as glycogen.  Plants can store carbohydrates as starch.

Chemically, carbohydrates are made up of carbon, hydrogen, and oxygen atoms.  The term “carbohydrate” reveals the chemical structure of the molecules; carbohydrates are hydrates of carbon, meaning they are carbon atoms with water added (or the constituent parts of water). The word “saccharide” is a synonym for carbohydrate that one finds in terms describing the structures of the different carbohydrates:

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