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
NOTE: : Sugars are less reactive in acid than in alkaline media : Disaccharides are less reactive than monosaccharides
Monosaccharide (from Greek monos: single, sacchar: sugar) are the most basic units of biologically important carbohydrates.
They are the simplest form of sugar and are usually colorless,water-soluble, crystalline solids Some monosaccharides have a sweet taste
add 10 drops of solution to 3 ml Barfoed’sReagnet, place in a boiling bath for 5 min Remove and allow to cool
Observe the results at once after 15 minutes of boiling.
NOTE: To ensure correct reading inspect carefully the presence of small amount of brick red precipitate.
Negative result Positive Result
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
The Barfoed’s Test is a chemical test carbohydrate that can be used to identify the existence of monosaccharides in the sample.
Heating the tubes beyond 10 minutes can result in hydrolysis of disaccharides to monosaccharides, thus producing a “false-positive” reaction.
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.
RCHO +2Cu2+ -> RCOOH + 4H+ +2H2O +Cu2O↓
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
Mucic Test Hear the sound of the Galactose
A test specifically useful in the identification of GALACTOSE
Mucic acid is another name of galactaric acid. Mucic acid test is named for the product of the reaction.
Galactose (from Greek γάλακτος galaktos "milk"), sometimes abbreviated Gal is a type of sugar that is less sweet than glucose. It is considered a nutritive sweetener because it has food energy. It is a C-4 epimer of glucose.
Galactose is a monosaccharide. When combined with glucose, through a dehydration reaction, the result is the disaccharide lactose.
Galactose and glucose are the two monosaccharide sugar components that make up the disaccharide sugar, lactose
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
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
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
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
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
A person with galactosemia doesn't have one of these enzymes. This causes high levels of galactose in the blood or urine.