Carbohydrates are among the most numerous compounds on earth, and they are generally divided into five main classifications of carbohydrates. Learn more about other names or carbohydrates.
Monosaccharides
The word monosaccharide is derived from mono, which means “one.” Each sugar has a cyclic structure and is composed of carbon, hydrogen, and oxygen in a ratio of 1: 2: 1, respectively. Although each sugar exists mainly as a cyclic compound, it must be in equilibrium with its linear shapes to a small degree.
Glucose
Glucose is the most important sugar that is metabolized by the body for energy. The D-isomer of glucose dominates in nature, and it is for this reason, the enzymes in our body have adapted to bind only this form. Sources of glucose include starch, the main form of storage for carbohydrates in plants.
Galactose
Galactose is almost identical to glucose in structure except for a hydroxyl group on carbon number four in the hexagonal sugar. Galactose is not usually found in nature in large quantities, but it is combined with glucose to form lactose in milk.
Fructose
Fructose is a structural isomer of glucose, which means that it has the same chemical form. Upon ingestion, fructose is absorbed and converted to glucose by the liver in the same way as lactose. Sources of fructose include fruit, honey, and high fructose corn syrup.
Disaccharides
Disaccharides, meaning “two sugars,” are often in nature as sucrose, lactose, and maltose. They are formed by a condensation reaction in which one molecule of water condenses or is released by combining two monosaccharides. The type of bond that is formed between the two sugars is called a glycoside bond.
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