Carbohydrates

This and the following pages conform the content included in :
Science Education Key Learning Area, Biology Curriculum and Assessment Guide (Advaned Level), Jointly prepared by the Curriculum Development Council and the Hong Kong Examination Authority 2002

1.1.1

*	The chemical structure of glucose .
*	The type of carbohydrates, monosaccharides (hexose and pentose), disaccharides (sucrose and maltose) and polysaccharides (cellulose, starch and glycogen).
*	The formation of glycosidic bond.
*	The function of carbohydrates as an energy source: glucose as an immediate energy source, starch and glycogen as storage compounds.
*	The function of carbohydrates as structural materials : cellulose as component of cell wall.
*	The functions of starch and cellulose in relation to their molecular structures, with a brief reference to a- and b- linkages.

Suggested Reading :

(1)	Advanced-level Biology for Hong Kong, by Y.K. Ho, SNP Manhattan Press (H.K.) Ltd. Bk 1, pp. 2-13
(2)	BIOLOGY for Advanced Level, 4th ed.,by Glenn and Susan Toole,Stanley Thornes : p.12 - 20
(3)	A-level Biology,by Phillips and Chilton,Oxford University Press : p. 11 - 16
(4)	Advanced Biology, principles and applications, ISE, by C.J. Clegg with D.G. Mackean, John Murray, pp 118 -130
(5)	Biology : Principles and Processes, by Roberts, Reiss and Monger, Nelson International Edition, pp.125 - 132

Carbohydrates is a type of organic compounds. Normally, they have backbones formed by carbon atoms.

Carbohydrates are so named for they contain hydrogen atoms and oxygen atoms besides the carbon atoms. Furthermore, the ratio between the hydrogen atoms and oxygen atoms is the same as that in water. So, it is regarded as the complexes of carbon and water.

Some simple carbohydrate molecules can serve as monomers in polymerization reactions. Then, these simple carbohydrate molecules are called monosaccharides. Glucose, fructose and galactose, all are monosaccharides.

Two monosaccharides can join together to form a dimer. The dimer is called a disaccharide. Sucrose, maltose and lactose are disaccharides.

Numerous monosaccharides can join together to form a polymer. The polymer is called a polysaccharide. Starch, cellulose, glycogen are examples of polysaccharides.

(28.08.2006)

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