mucic and barfoeds test
TRANSCRIPT
BARFOED’S TEST
Knowing who’s Lonely ;)
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
PROCEDURE
add 10 drops of solution to 3 ml Barfoed’s
Reagnet,
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
RESULTS
Barfoeds
Test
Test solutions (1% W/V)
Galactose Glucose Fructose Maltose Sucrose Xylose
:first 5
minutes
+ Low
precipitate
+ Low
precipitate
+low
precipitate
- No
precipiate
+low
precipitate
+ low
precipitate
:next
15
minutes
+High
precipitate
+High
precipitate
+High
precipitate
+High
precipitate
+High
precipitate
+High
precipitate
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 TESTHear 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
PROCEDURE
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
RESULTS
Test solutions (1% W/V)
Galactose Glucose Fructose Maltose Sucrose Xylose
Mucic
Test
Positive
-presence
of crystals
None None None None None
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
HC=O-(CHOH)4-COOH (aq) + 2 HNO3 (aq)
------>
HOC=O-(CHOH)4-COOH (s) + H2O (l) + 2 NO2
OHCH2OH
O
OHOH
OH
HNO3
OHCOOH
OH
OHOH
COOH
APPLICATION
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.