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Disaccharide
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<p>A disaccharide (also called a double sugar or <i>biose</i>) is the <a href="/facts/Sugar/jb5KXRHT">sugar</a> formed when two <a href="/facts/Monosaccharide/yzs2d6Eq">monosaccharides</a> are joined by <a href="/facts/Glycosidic_linkage/xhYwU6sl">glycosidic linkage</a>. Like monosaccharides, disaccharides are simple sugars <a href="/facts/Solubility/kLE9h3Jb">soluble</a> in water. Three common examples are <a href="/facts/Sucrose/7y1ke94L">sucrose</a>, <a href="/facts/Lactose/lBa5ozYk">lactose</a>, and <a href="/facts/Maltose/v43CVtaU">maltose</a>. </p><p>Disaccharides are one of the four chemical groupings of <a href="/facts/Carbohydrate/Geuuzxsf">carbohydrates</a> (monosaccharides, disaccharides, <a href="/facts/Oligosaccharide/5to180o3">oligosaccharides</a>, and <a href="/facts/Polysaccharide/lqXq2cJU">polysaccharides</a>). The most common types of disaccharides—sucrose, lactose, and maltose—have 12 <a href="/facts/Carbon/ukrgQexo">carbon</a> atoms, with the general formula C12H22O11. The differences in these disaccharides are due to <a href="/facts/Isomer/PXlvDVdg">atomic arrangements within the molecule</a>. </p><p>The joining of monosaccharides into a double sugar happens by a <a href="/facts/Condensation_reaction/wMG0F6La">condensation reaction</a>, which involves the elimination of a water molecule from the <a href="/facts/Functional_group/GXkSPsjM">functional groups</a> only. Breaking apart a double sugar into its two monosaccharides is accomplished by <a href="/facts/Hydrolysis/JTvwIHPs">hydrolysis</a> with the help of a type of <a href="/facts/Enzyme/DSI1Fh7y">enzyme</a> called a <a href="/facts/Disaccharidase/TwGJ4y00">disaccharidase</a>. As building the larger sugar ejects a water molecule, breaking it down consumes a water molecule. These reactions are vital in <a href="/facts/Metabolism/WxDrm8k5">metabolism</a>. Each disaccharide is broken down with the help of a corresponding disaccharidase (<a href="/facts/Sucrase/lkaPJf3h">sucrase</a>, <a href="/facts/Lactase/DxrPlfwB">lactase</a>, and <a href="/facts/Maltase/gkHcal0y">maltase</a>). </p>