CARBOHYDRATES 39 



single disaccharide molecule to split into two monosaccharide (hexose) 

 molecules. The products of the hydrolysis of the more common di- 

 saccharides are as follows: 



Maltose = glucose -{-glucose. 

 Lactose = glucose -f-galactose. 

 Sucrose = glucose + fructose. 



All of the more common disaccharides except sucrose have the power 

 of reducing certain metallic oxides in alkaline solution, notably those 

 of copper and bismuth. This reducing power is due to the presence 

 of the aldehyde group ( CHO) in the sugar molecule. 



MALTOSE, Ci 2 H 22 On 



Maltose or malt sugar is formed in the hydrolysis of starch through 

 the action of an enzyme, vegetable amylase (diastase), contained in sprout- 

 ing barley or malt. Certain enzymes in the saliva and in the pancreatic 

 juice may also cause a similar hydrolysis. Maltose is also an intermedi- 

 ate product of the action of dilute mineral acids upon starch. It is 

 strongly dextro-rotatory, reduces metallic oxides in alkaline solution 

 and is fermentable by yeast after being inverted (see Polysaccharides, 

 page 43) by the enzyme maltase of the yeast. In common with the other 

 disaccharides, maltose may be hydrolyzed with the formation of two 

 molecules of monosaccharide. In this instance the products are two 

 molecules of glucose. With phenylhydrazine maltose forms an osa- 

 zone, maltosazone. The following formula represents the probable 

 structure of maltose: 



CH 2 OH CHO 



I I 



CHOH CHOH 



Maltose. 



EXPERIMENTS ON MALTOSE 



1-6. Repeat Solubility, Fehling's, Nylander's, Phenylhydrazine, Barfoed's 

 and Fermentation tests as given under Glucose, pages 21-31. 



