2. A biochemical test to detect monosaccharide (reducing) sugars in solution Disaccharides will also respond to the test with prolonged heating and under proper conditions of acidity leading to hydrolysis of the disaccharides
3. NOTE: : Sugars are less reactive in acid than in alkaline media : Disaccharides are less reactive than monosaccharides
13. Discussions Barfoed's Test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of copper(II) acetate to copper(I) oxide (Cu2O), which forms a brick-red precipitate
15. Heating the tubes beyond 10 minutes can result in hydrolysis of disaccharides to monosaccharides, thus producing a “false-positive” reaction.
16. Barfoed's reagent consists of a 0.33 molar solution of neutral copper acetate in 1% acetic acid solution. The reagent does not keep well and it is therefore advisable to make it up when it is actually required.
18. application Lactose Intolerance- Congenital disorder consisting of an inability to digest milk and milk products; absence or deficiency of lactase results in an inability to hydrolyse lactose
26. THREE principal derivatives of Aldoses Aldonic Acids(alcohol Acids)- the aldehyde is oxidized Uronic Acid- those in which the primary alcohol group is oxidized Saccharic acids- both the aldehyde and primary alcohol groups are oxidized
28. Place 2ml of the test solution in a large test tube Add to 5ml of concentrated Nitric Acid Place the tube in the boiling water bath for one Hour Scratch the inner wall of the tube with glass rod Let it stand for 30-45 min or overnight if no crystals were formed. Examine the crystals on the microscope
31. DISCUSSIONS The aldehyde and primary alcohol groups are oxidized to CARBOXYL groups in the reaction of galactose with HNO3 forming Saccharic Acid The saccharic acid formed from the free or combined glucose is insoluble and seperates out as colourless crystals in the cold
35. Galactose is a component of the antigens present on blood cells that determine blood type within the ABO blood group system Determining Galactose present on urine
36. Galactosemia- A genetic in which an enzyme needed to metabolize galactose is deficient or absent; typically develops shortly after birth A galactosemia test is a blood test (from the heel of the infant) or urine test that checks for three enzymes that are needed to change galactose sugar that is found in milk and milk products-into glucose, a sugar that your body uses for energy
37. A person with galactosemia doesn't have one of these enzymes. This causes high levels of galactose in the blood or urine.
Notas do Editor
The test as performed is used to diffrentiate monosaccharides from disaccharides. It is not a specific test for glucose serving simply to detect monosaccharides.Barfoeds test is unsuited for the detetion of sugar in urine or in any fluid containing chlorides.
GOING BACK to the concepts in Biochemistry. Three principal derivatives of aldoses derived by appropriate oxidation to carboxylic acids.The oxidation of the aldehyde and primary alcohol groups are practically useful in the identification of galactose.
In the reaction of galactose with the oxidizing agent HNO3 the aldehyde and primary alcohol groups are oxidized to carboxyl groups.While sacc