CHAPTER V 



CARBOHYDRATES 



The carbohydrates which occur in plants may be classified as follows : 



Pentoses, C5H10O5 — Arabinose, xylose. 

 Methyl pentoses, C5H9O5 * CH3 — Rhamnose,. 



isorhamnose. 

 Hexoses, CeHigO^ — Glucose, galactose, 



mannose, laevulose. 



Disaccharides (Sucrose, maltose, CiaHgaOn . 



Trisaccharides (Raffinose and others. 



Tetrasaccharides (Stachyose. 



Monosaccharides . 



Polysaccharides 



Pentosans, (C6H804)n — Araban, xylan. 

 Starches, (CeHioOs),^ — Starch, dextrin, inulin. 

 Mannans, galactans, gums, mucilages, 



pectic substances. 

 Celluloses, (C6Hio05)n. 



The carbohydrates are widely distributed in plants and form most 

 important parts of their structure. Those most commonly found are : 

 cellulose, starch, pentosans, dextrin, glucose, sucrose, laevulose, and 

 maltose. Other sugars, especially trisaccharides, are known in addition 

 to those mentioned above, but they are somewhat restricted and specific 

 in their distribution. 



As in the case of the proteins, so with the carbohydrates, the molecules 

 of the more simple and soluble crystalline compounds, such as the mono- 

 saccharides, are synthesized into more complex molecules which exist, 

 either in the colloidal (dextrin), or insoluble state (starch, cellulose). 

 The last-mentioned build up parts of the solid structure of the plant. 

 The resolution of the solid complex substances into simple ones is known 

 in many instances to be brought about in the plant by enzymes, and it 

 is highly probable that the synthesis of the complex from the simple is 

 also controlled by these enzymes. 



