Revision Biology - Carbohydrates

Revision for Biology - carbohydrates. Spec: OCR

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  • Created on: 17-05-10 17:26
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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,
glucose 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
A disaccharide is formed when two monosaccharide join together.
Two glucose molecules join together by a glycosidic bond to form maltose.
A polysaccharide is formed when more than two monosaccharide join together.
Lots of 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 glucose ­ amylose and amylopectin.
Amylose ­ Long, unbranched chain of 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 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
Glycogen ­ The main energy storage material in animals

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Cells get energy from glucose. Animals store excess glucose as glycogen ­ another
polysaccharide of glucose.
Long, branched, lots of side branches ­ lots of side branches means that stored glucose can
be released quickly, which is important for energy release in animals.
Very compact molecule ­ good for storage.
Cellulose ­ Major component of cell walls in plants
Long, unbranched chains of glucose.
The bonds between the sugars are straight, so the cellulose chains are straight.…read more


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