62 



GENERAL BIOCHEMISTRY 



derivative in aloes and with L-arabinose in the pathological states men- 

 tioned above. See the structural formula below. 



D-Ribose 



This aldopentose occurs in various derivatives of metabolic interest. 

 D-Ribose is one of the components obtained on hydrolysis of the ribo- 

 nucleic acids. These macromolecules contain phosphate and organic 

 bases in addition to the sugar. They are essential to life as we know 

 it, although their function is not well established. Certain viruses 

 contain ribose, once again in the form of ribonucleic acid. 



D-Deoxyribose 



This sugar resembles ribose itself in occurrence. The deoxyribo- 

 nucleic acids occur in some viruses and in all living cells, where they 

 are involved in cell division and carry the hereditary traits. The 

 nucleic acids are discussed more fully starting with page 120. As in- 

 dicated by the prefix, this sugar has no oxgyen atom on carbon two 

 but is otherwise like n-ribose. 



D-Xylose 



This carbohydrate occurs in wood, straw, and other fibrous mate- 

 rials in combined forms from which it is obtained on hydrolysis. Small 



-O 



HO 



I / 



C 



I \ 



H 



H 



1 

 C- 



H 



OH H 



C C 



H 



J 

 C 



OH 



CHoOH 



O 



C 

 H 



H 

 C- 



H 



C 



H 



C 

 OH 



H OH 



^-L-arabinose 

 CH2OH 



o 



/ \ 



c 



r 



H 



H H 



\l 1/ 

 C C 



I I 

 OH H 



a-D-deoxyribose 



H 



G 



'I 

 OH 



H 



L 

 c 



OH OH 



a-D-ribo8C 



H 



I 

 C- 



H 



OH\ 



O 



OH H 



H OH 



a-D-xvlose 



H 



J 

 C 



OH 



