THE CONSTITUENTS OF BIOSPHERE 



19 



HO H 



\ / 



C 



H— C— OH 



I 

 HO— C— H 



I 

 H— C— OH 



H— C 



O 



CH.OH 



j3-D-glucose 



H— C=0 



H— C— OH 



I 

 HO— C— H 



H— C— OH 



H— C— OH 



I 

 CH.OH 



D-glucose chain molecules 

 (traces) 



H OH 



\ / 

 C 



H— C— OH 

 HO— C— H 

 H— C— OH 

 H— C 



O 



CHoOH 



a-D-glucose 



In the above formulae the ring is made up of five carbon atoms and an 

 oxygen atom, but in addition the presence has been demonstrated in 

 solutions of the sugars of molecules in which the ring is made up of four 

 carbon atoms and one oxygen atom, and derivatives of these forms have 

 been prepared. Because these rings correspond to those of furan and pyran, 

 Haworth has proposed a terminolog}^ in which the sugars are considered as 

 derivatives of these structures. 



O 



/\ 

 HC CH 



II II 



HC CH 



\/ 

 C 



Pyran 



o 



/ \ 



HC CH 



\ // 



c— c 



H H 



Furan 



The pyranose and furanose formulae are drawn in perspective looking 

 down on the ring, each of the corners representing a carbon atom. 



The atoms whose symbols are written above the ring are situated above 

 the plane of the ring and those whose symbols are written below are 

 situated below the plane of the ring. These formulae contain an asymmetric 

 carbon atom additional to those present in the linear formulae and this is 

 the one which, in D-glucopyranose, for example, is in position 1. 



