V] 



HYDROLYZING ENZYMES 



47 



CHO 



H— C— OH 



I 

 H— C~OH 



I 

 HO— C H 



I 

 CH.OH 



/-Galactose 



CHO 



I 

 H— C OH 



I 

 HO— C- H 



i 

 HO— C— H 



I 

 H— C— OH 



CH.OH 



o?-Galac'ti)se 



CHO 



I 

 H— C— OH 



I 

 H— C- OH 



I 

 H— C— OH 



i 

 HO— C -H 



I 

 CH,,OH 



^Talose 



CHO 



I 

 HO— C— H 



I 

 HO C— H 



I 

 HO— C— H 



I 

 H— C— OH 



I 

 CH.OH 



o?-Talo«e 



CHO 



HO— C— H 



I 

 HO— C— H 



I 

 HO— C— H 



I 

 HO— C— H 



I 

 CH.OH 



CHO 



I 

 H— C— OH 



I 

 H— C— OH 



I 

 H C— OH 



CHO 



I 

 H— C— OH 



I 

 HO— C— H 



HO— C— H 



H— C— OH HO— C— H 



CH2OH CH.OH 



These four unknown 



CHO 

 I 

 HO— C— H 



I 

 H— C— OH 



I 

 H— C— OH 



I 

 H— C— OH 



I 

 CH.OH 



Though many of the above sugars have been synthesized artificially, 

 only three are known to occur naturally, i.e c?-glucose (dextrose or grape- 

 sugar), c?-mannose and cZ-galactose. 



Since compounds containing asymmetric carbon atoms are opticallv 

 active, i.e. can rotate a plane of polarized light, it follows that the sugars 

 under discussion are optically active. 



c?-glucose is dextro-rotatory. 



When either d- or ^glucose is first dissolved in water, it is chemically 

 less active than would be expected of the aldehyde *form depicted above. 

 This is explained by assuming that glucose, when first dissolved in water, 

 exists in the condition of a 7-lactone : 



