Practical Carbohydrates PDF

# Understand & Enjoy Bio Carbohydrates ## [1st Year: Foundation Module - practical] ### TESTS - **Q: Is the solution CHO or protein?** - **Test:** Biuret test (2 ml solution + 2 ml NaOH, 2 drops of CuSo4, mix). - **Blue** - **CHO** - **Violet** - **Pep...

# Understand & Enjoy Bio Carbohydrates ## [1st Year: Foundation Module - practical] ### TESTS - **Q: Is the solution CHO or protein?** - **Test:** Biuret test (2 ml solution + 2 ml NaOH, 2 drops of CuSo4, mix). - **Blue** - **CHO** - **Violet** - **Peptide bond** - **Protein** - **Principles:** - detect the presence of peptide bonds. - In the presence of peptides, copper(II) ion forms violet‐colored coordination complexes in an alkaline solution. - This test is given by all proteins containing more than 2 peptide bonds - **Q: Is the solution CHO or not?** - **Test:** Molisch test (2 ml solution + 2 drops of naphthol, concentrated H2So4). - **CHO** - **Violet ring between two solutions** - **Not CHO** - **No violet ring** - **Principles:** - Sugars are dehydrated by H2So4 forming Furfural (in pentoses) or (hydroxy methyl furfural) (in hexoses). - Which condenses with a.naphthol giving colored product. - **Q: Is the solution simple or complex sugar?** - **Test:** iodine test (2 ml solution + 2 ml iodine yellow). - **Simple sugar** - All mono or disaccharide - (No change in yellow color) - **Complex sugars** - Starch - (Change yellow to deep blue color) - **Q: Is the sugar reducing or non‐reducing?** - **Test:** Benedict test - **Other test:** Fehling test - **Benedict test: ** (Benedict reagent, CuSo4) - **Red ppt.** - **Sugar is reducing** - Maltose, Lactose, Mono. - **No red ppt** - **Sugar is non reducing** - only sucrose. - **Principles:** - 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. - **NB** - Benedict is more sensitive than Fehling - **Q: Is the solution mono or disaccharide?** - **Test:** Barfoed test (Barfoed reagent: CuSO4 in acetic Acid) - **Red Ring/ppt** - **Monosaccharide give** - **Red ppt before 5 minutes** - **No red ppt** - **Disaccharide** - **Principles:** - 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. - **Q: Does the sugar contain ketone bodies or not?** - **Test:** Ketose test (Acid: conc. HCI) - **Ketose test** - **Other test:** Seliwanof test - **Same as ketose** - **Deep red** - **Sugar is fructose (contain Ketone group)** - **No deep red color** - **Not contain Ketone group** - Ex: Glucose. - **Principles:** - They detect the presence of ketone group. - **Q: Is this protein coagulable or not?** - **Test:** heat coagulation test. - **White opacity in upper tube** - **Coagulable protein** - Ex:Albumin - **No opacity** - **Non coagulable** - Ex Casein or Peptone - **Test:** hellers test Reagent: Nitric acid - **White ring at junction of 2 solution** - **If coagulable protein (Albumin & globulin)** - **If no:** Casein and peptone - **Q: It is casein or peptone?** - **Test:** Acidification test - **Acid:** acetic acid - **White ppt** - **Casein** - **No white ppt** - **Peptone** - **Q: Yellow tube + paper (Litmus paper)** - **Is it casein or peptone?** - **Blue paper:** Casein - **As casein (alkaline convert litmus paper from red to blue).** - **Use:** differentiate between casein, peptone ## Dr. Mostafa El-Fallaha ## 4