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2.3.3. Pentoses


They are carbohydrates made up of chains of five carbon atoms.

The aldopentoses have three asymmetric carbons (C2 ,C3 and C4), so there are eight possible molecular structures (23 = 8). Only four are found in nature:

  • D-ribose, in ribonucleic acid .
  • D-2 -deoxyribose, in deoxyribonucleic acid .
  • D-xylose, a component of the wood xylan polysaccharide .
  • L-arabinose, forming the polysaccharide arabana , which is one of the components of gum arabic.

Among the ketopentoses, mention should be made of D-ribulose, which plays a fundamental role in photosynthesis, since it binds to the carbon dioxide (CO2) molecule, introducing it into organic matter.

Pentosas: ribosa y desoxirribosa.

Fundamental ideas about pentoses

The most important aldopentoses are ribose and deoxyribose. The difference between ribose and deoxyribose is that deoxyribose lacks an oxygen and at carbon 2.

Its function is fundamentally structural, ribose being part of RNA and deoxyribose, of DNA.