تسجيل الدخول

تسجيل

Classification of Carbohydrates

المؤلف:  ..................

المصدر:  LibreTexts Project

الجزء والصفحة:  .................

3-12-2019

2360

Classification of Carbohydrates

Carbohydrates are the most abundant class of organic compounds found in living organisms. They originate as products of photosynthesis, an endothermic reductive condensation of carbon dioxide requiring light energy and the pigment chlorophyll.

nCO₂+nH₂O+Energy→C_nH_2nO_n+nO₂

As noted here, the formulas of many carbohydrates can be written as carbon hydrates, Cn(H2O)n , hence their name. The carbohydrates are a major source of metabolic energy, both for plants and for animals that depend on plants for food. Aside from the sugars and starches that meet this vital nutritional role, carbohydrates also serve as a structural material (cellulose), a component of the energy transport compound ATP/ADP, recognition sites on cell surfaces, and one of three essential components of DNA and RNA.

Carbohydrates are called saccharides or, if they are relatively small, sugars. Several classifications of carbohydrates have proven useful, and are outlined in the following table.

Complexity Simple Carbohydrates monosaccharides Complex Carbohydrates disaccharides, oligosaccharides & polysaccharides

Size Tetrose C4 sugars Pentose C5 sugars Hexose C6 sugars Heptose C7 sugars etc.

C=O Function Aldose sugars having an aldehyde function or an acetal equivalent. Ketose sugars having a ketone function or an acetal equivalent.

Reactivity Reducing sugars oxidized by Tollens' reagent (or Benedict's or Fehling's reagents). Non-reducing sugars not oxidized by Tollens' or other reagents.