78 THE ACTION OF ENZYMES 



termed dextrose), and fructose^ or fruit-sugar (sometimes 

 called laevulose). Both have the empirical formula, 

 C 6 H 12 O 6 . A mixture of these two sugars are formed 

 when the cane-sugar is " inverted " by boiling with acids, 

 or by the action of certain enzymes. 



(a) Glucose or Grape-sugar is found in company with 

 an equal amount of fructose in most ripe fruits, and can 

 be produced by the hydrolysis of starch, cellulose, and 

 other polysaccharoses, the change being effected by 

 boiling with dilute sulphuric acid. It is not very sweet. 



(b) Fructose or Fruit-sugar is met with in fruits along 

 with grape-sugar, as stated above, and in " invert-sugar." 



(c) Galactose is another monosaccharose of the same 

 empirical composition as the two preceding compounds, 

 and is prepared by boiling milk-sugar or certain gums 

 with dilute sulphuric acid. 



These sugars reduce Fehling's solution, and are directly 

 fermentable by yeast and certain species of bacteria. 



Ex. 44. Dissolve 35 grams of copper sulphate in 500 c.c. of 

 water, label this solution A: then dissolve 160 grams of caustic 

 potash and 173 grams of sodium potassium tartrate in 500 c.c. 

 of water and label the solution B. By mixing equal quantities 

 of A and B, Fehling's solution is produced. (The solution A 

 and B should be kept separate and only mixed when needed, as 

 the mixture does not keep long.) 



Squeeze a few drops of grape juice into a test-tube containing 

 10 c.c. of the Fehling's solution : heat over a Bunsen flame and 

 note the reddish precipitate of cuprous oxide (Cu 2 O). 



Test the juice of ripe plums and other fruits in^the same way. 



2. Fats and Oils : Lipase. Fats and oils contain 

 the same elements as carbohydrates, namely, carbon, 

 hydrogen, and oxygen, but the oxygen is in smaller pro- 

 portion to the hydrogen than in the latter compound. 



