General Carbohydrate Scheme PDF

Department of medical biochemistry and molecular biology Faculty of medicine menoufia university By the end of this section students must know: 1- Must be able to classify carbohydrate. 2- Be able to differentiate between different sugars of carbohydrate. 3- Perform chemi...

Department of medical biochemistry and molecular biology Faculty of medicine menoufia university By the end of this section students must know: 1- Must be able to classify carbohydrate. 2- Be able to differentiate between different sugars of carbohydrate. 3- Perform chemical tests to identify the sugar. Volume: random sample Taste: sweety Aspect: clear (except starch turbid) Odour: odourless Reaction: neutral Colour: colourless (except starch greyish white)  Carbohydrates Simple sugars complex monosaccharaides disaccharides polysaccharides  2m1 of 0.5% of the sugar solution in a test tube + 2 drops of - naphthol and mix well. 2ml of conc. H2SO4 Violet ring between 2 solutions  Principle:  In the presence of conc. H2SO4 sugars are dehydrated forming furfural (in pentoses) or hydroxymethylfurfural (in hexoses) which condense with -Naphthol giving colored condensation products  this test is given by all carbohydrates It is used to differentiate between simple sugars (mono and disaccharides) and polysaccharides. A few drops of iodine + 2 ml of the carbohydrate solution. No change in yellow colour blue-black colour of iodine Simple sugar polysaccharide (starch)  It is used to differentiate between reducing and non reducing sugars  All mono and disaccharides are reducing except sucrose.  Polysaccharides are non reducing.  Procedure: 1 ml of CHO solution + 5 ml of benedict reagent No red ppt Red ppt Non reducing sugar Reducing sugar  Principle: Reducing sugars reduce soluble blue copper sulphate, containing Cu2+ ions in the benedict reagent to insoluble red-brown copper oxide containing Cu+ which is seen as a precipitate. N.B. benedict is more sensitive than Fehling  It is used to differentiate between mono and disaccharides  Procedure: 1 ml of the sugar solution + 3ml of Barfoed’s reagent then heat in a boiling water- bath for 5 minutes. Monosaccharide disaccharide (before 5 min) (after 5 min)  Principle: - Barfoed’s reagent is composed of a solution of cupric acetate in dilute acetic acid. - In acidic medium, barfoed's reagent reacts with monosaccharides to produce cuprous oxide at a faster rate than disaccharides.  They are used to differentiate between ketoses (fructose, sucrose) and aldoses (glucose).  Principle: They detect the presence of ketone group.  Pocedure: 1 ml of CHO solution + 3ml of seliwanof reagent then boil in water- bath. No change in colour cherry red colour Glucose fructose/sucrose  Pocedure: 2 ml of CHO solution + 2 ml of conc. HCL then boil. No change in colour deep red colour Glucose fructose/sucrose