Carbohydrates Essay

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Revision – Carbohydrates Carbohydrates are made from monosaccharides * Carbohydrates are long and complex molecules made of long chains of monosaccharides. * Single monosaccharides are also called carbohydrates. * Glucose is a carbohydrate composed of 6 carbons. There are two forms of glucose, α glucose β glucose Glucose is soluble so it can be easily transported. Monosaccharides join together to form disaccharides * Monosaccharides are joined together by glycosidic bonds. * During a condensation reaction, the hydrogen from one monosaccharide joins to the hydroxyl group on another monosaccharide releasing a molecule of water forming a glycosidic bond. The reverse of this is hydrolysis reaction where a water molecule is used up to break the bond. * A disaccharide is formed when two monosaccharide join together. Two α glucose molecules join together by a glycosidic bond to form maltose. * A polysaccharide is formed when more than two monosaccharide join together. Lots of α glucose molecules are joined together by glycosidic bonds to form amylose. Starch – Main energy storage materials in plants * Cells get energy from glucose; excess glucose is stored as starch. When a plant needs more glucose, it breaks down the starch into glucose. * Starch is a mixture of 2 polysaccharides of α glucose – amylose and amylopectin.Amylose – Long, unbranched chain of α glucose. The angles of the glycosidic bonds give it a coiled structure. This makes it compact, so it’s good for storage.Amylopectin – Long, branched chain of α glucose. Its side branches allow the enzymes that break down the molecules to get at the glycosidic bond easily. This means the glucose can be released quickly. * Starch is insoluble in water so it doesn’t to enter cells by osmosis. This makes it good for storage. | Glycogen – The main energy
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