CHAPTER 4CHAPTER 4

CHEMICAL CHEMICAL COMPOSITION OF THE COMPOSITION OF THE

CELLCELL

4.2 CARBOHYDRATES4.2 CARBOHYDRATES

Nur amni syazanaNur amni syazana

CARBOHYDRATES• Source of energy• Build cell walls of plants• Form external skeleton of insects• As food storage• Consists of carbon,hydrogen and oxygen• Ratio of hydrogen atoms to oxygen atoms

molecule is 2:1

TYPES OF CARBOHYDRATES

MONOSACCHARIDES

POLYSACCHARIDES

DISACCHARIDES

MONOSACCHARIDESThe basic building blocks of carbohydrates

(monomers of carbohydrates) Known as simple sugarReducing sugars

EXAMPLE:Glucose ~ in plants and fruitsFructose ~ in sweet fruits and

honeyGalactose ~ in milk

DISACCHARIDESReducing sugars except sucroseConsist of two monosaccharidesComplex sugars

EXAMPLE:GLUCOSE + GLUCOSE -> Maltose (malt sugar)GLUCOSE + FRUCTOSE -> Sucrose (cane sugar)GLUCOSE + GALACTOSE -> Lactose (milk sugar)

GLUCOSE + GLUCOSE ------------------->MALTOSE + WATER condensation

GLUCOSE + GLUCOSE <-------------------MALTOSE + WATERhydrolysis

POLYSACCHARIDESCombination of hundreds of monosaccharidesFormed by the condesation of glucose monomersDo not taste sweet and do not crystalliseInsoluble in water

EXAMPLE:Glycogen ~ in animal and yeast

~ known as animal starch

Starch ~ stores in plants (rice,corn,bread,wheat)Cellulose ~ form cell wall in plants

GLUCOSE + GLUCOSE ------------------->MALTOSE + WATERhydrolysis