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Carbohydrate 1


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Carbohydrate 1

  1. 1. CarbohydratesDr. Khalid Hussain
  2. 2. Introduction• Chemically: Polyhydroxy aldehydes and ketones• Have hydrogen and oxygen in a ratio of water (2:1) Ribose (C5H10O5) and Glucose (C6H12O6)
  3. 3. • General formula Cn(H2O)n.Hence, also called hydrates of carbon• Substances which are converted into polyhydroxy aldehydes and ketones after hydrolysis
  4. 4. Importance of carbohydrates• Provide major source of energy (4.1C)• Serve also as stored forms of energy as glycogen in liver and muscles• Protein sparing action• Reduce breakdown of fatty acids and preventing ketosis• Involved in biological recognition processes of immunoglobulin
  5. 5. Contn’d• Flavoring and Sweetening agents• Dietary fiber (Cellulose)• Important components of brain cells as neuraminic acids, cerebrosides (Glycolipids) and gangliosides• Important component of nucleic acids as pentose sugars - ribose and deoxyribose
  6. 6. Contn’d• Function as physiological anticoagulant (Heparin)• Plasma expanders (Dextran)• Parenteral nutrition• Binders in tablets• Disintegrators in tablets• Analytical techniques: Agar agar and starch• Diagnostic markers
  7. 7. Classification• Have been classified into 4 main groups – Monosaccharides – Disaccharides – Oligosaccharides – Polysaccharides
  8. 8. Monosaccharides• Carbohydrates which can’t further be broken down into simpler units by acid hydrolysis• Classified according to the number of carbon atoms present in them – For example trioses, tetroses and hexoses
  9. 9. • Usually have 3-9 carbon atoms• Further sub-classified into aldoses and ketoses• Exact name is based on – number of carbons atoms – presence of aldehyde or ketone groups – i.e aldotriose or ketotriose
  10. 10. Aldotrioses/ C3 H 6 O 3 Glyceraldehyde and dihydroxyketotrioses acetoneAldotetroses/ C4 H 8 O 4 Erythrose, ErythruloseketotetrosesAldopentoses/ C5H10O5 Ribose , RibuloseketopentosesAldohexoses/ C6H12O6 Glucose, Fructoseketohesoses Erythrose Ribose Ribulose
  11. 11. • Monosaccharides also include derivatives of above mentioned monosaccharides e.g. amino sugars, sugar alcohols, sugar acids and esters of sulfuric acid and phosphoric acid
  12. 12. Disaccharides• Biose• Formed when two monosaccharides undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only Sucrose
  13. 13. Oligosaccharides• Greek word oligos, meaning "a few", and sacchar which means "sugar“• Saccharide polymers containing a small number (typically three to ten) of component sugars- Monosaccharides For example Raffinose
  14. 14. Polysaccharides• Polymeric carbohydrate structures, formed by repeating units (either mono- or di- saccharides) joined together by glycoside bond• Such structures are often linear, but may contain various degrees of branching• Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit
  15. 15. • When all the monosaccharides in a polysaccharide are of same type the polysaccharide is called a homopolysaccharide: starch and glycogen, but when more than one type of monosaccharides are present, they are called heteropolysaccharides: pectin, lignin• Polysaccharides have a general formula of (C6H10O5)n• Not sweet, hence called non-sugars
  16. 16. CH2OH 6CH OH CH2OH CH2OH CH2OH 2 O 5 O H O H O H H O HH H H H H H H H H H OH H 1 4 OH H 1 OH H OH H OH H O O O O OHOH 2 3 H OH H OH H OH H OH H OH amylose CH2OH 6CH OH CH2OH CH2OH CH2OH 2 O 5 O O H O H O OH H H H H H H H H OH H 1 O 4 OH H 1 O OH H O OH H O OH H OH H H H H 2 H 3 H OH H OH H OH H OH H OH cellulose Upon acid hydrolysis produce monosaccharides
  17. 17. Significance• Key role in maintaining energy balance in the biosphere• Building blocks and source of energy• Used as excipients in pharmaceuticals Dusting Powders, disintegrant, mucilage• Bio-markers• As Medicine –heparin, glucose, dextran etc.• Chromatography and electrophoresis
  18. 18. Oxidation of glucose• Mild oxidizing agents such as bromine water convert glucose to gluconic acid, which is single step reaction• This reaction is used to differentiate sugars having – CHO (reducing) group or those yielding such group
  19. 19. Example is Fehlings solution test• Fehlings solution is composed of equal parts of two solutions:1-Fehlings solution A 69.28 grams copper sulfate pentahydrate dissolved in 1 litre of distilled water2-Fehlings Solution B 346 grams potassium sodium tartrate and 120 grams sodium hydroxide in 1 litre of distilled water
  20. 20. Fructose also give positive test• Under alkaline conditions fructose is converted to glucose and mannose
  21. 21. Tollens reagent test "silver mirror"• Tollens reagent: when silver nitrate solution is treated with sodium hydroxide(NaOH) till it forms precipitate and then NH4OH is added till the precipitate is dissolved- Ag(NH3)2]+• The diammine silver complex is an oxidizing agent, which is itself reduced to silver metal