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Ma Jasmin Magsumbol

on 11 December 2015

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Hydrolysis of Starch with Acid
3 mL of 1% Potato Starch + 2 gtts of Lugol's Solution
1mL of glycogen solution+ 3 gtts of Lugol's sol.
Result: Reddish brown solution
One test for reducing sugars involves Fehling’s reagent, which contains Cu2+ ions in an aqueous basic solution.
If a reducing agent is present, the Cu2+ is reduced to Cu+ and forms a red precipitate of Cu2O. Therefore, if Fehling’s solution is added to a solution containing a reducing sugar, a red precipitate will form.
Schweitzer's test
Schweitzer's reagent+filter paper+distilled water+acetic acid
Iodine test for Cellulose
Lugol's Solution+shreds of cotton

If a blue color is developed. That means there is cellulose present
This test is based on the conversion of cellulose into amyloid, which gives a blue color with Lugol's iodine.
Test for Glycogen
Test for cellulose
Laboratory Equipments:
Laboratory Equipments:
Wire gauze
Water bath
Test tubes
Test tube rack
Mortar and Pestle
Test tube brush
Muslin cloth
Bunsen burner
Chemical Reagents:
Lugol's Solution
50% NaOH Solution
Fehling's Reagent
Concentrated HCl
Ethyl Alcohol
Dilute HCl
Acetic Acid Solution
Expected result: Blue Solution
Heated 3 mL of 1% Potato Starch + 2 gtts of Lugol's Solution
Obtained result: Colorless liquid
Experimental result: Blue Solution
Heating the mixture can cause the breaking of hydrogen bonds. Thus, the color will disappear but will reappear if cooled.
Reagents used:
Starch Solution
50% NaOH
dilute HCL
Fehling's Solution
Result: Red precipitate
Fehling's Solution is used for testing reducing sugars. The 5% glucose solution reacted with the Fehling's solution and resulted to red precipitate
++++ (Strongly positive)
+++,++,+ (Succeeding intensities of positive result)
- (negative result)
Heating of starch in the presence of conc. HCl causes its hydrolysis into glucose. because glucose have free Aldehyde group, therefore it is a strongly reducing monosaccharide, and hence Benedict’s, Selivanoff’s and Osazone tests become positive.
Other sources of Starch:
Some fruits
With Fehling's Solution: The mixture turned to blue
Other sources of glycogen:
Glycogen is the molecule which functions as the secondary short term energy storage in animal cells. It is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach.
End product of hydrolysis of glycogen: glucose-1-phosphate
Difference between starch and glycogen:
Glycogen consists of a single molecule and its structure is branched purely. Starch is made of two molecules and their structure is composed of a chain and branch
Achromatic Point
It is the point where starch does not give a colored solution during the iodine test.
Produced: copper-ammonium silk
Cellulose molecule (C 6 H 10 O 5) n or [C 6 H 7 O 2 (OH)3 ] n is built from a large number of interconnected residues of D-glucopyranose each of them has three hydroxyl groups, hydrogen atoms from these groups at the adding of Schweitzer’s reagent are replaced on the copper atom (as in a polyhydric alcohols) and form a water soluble complex of copper cellulosate.
At the dissolution of cellulose in copper-ammonium complex two hydrogen atoms of hydroxyl groups are replaced by copper atom and hydrogen atom of the third OH-group is ionized. Therefore glucose residues in cellulose keep their linkages and form anions (C 6 H 7 O 5 Cu) -, which combine with ammonia. This leads to the dissolution of cellulose.


S.C., Nigam. Experimental Animal Physiology and Biochemistry. p.15





Group 4 (BSPh-2A)
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Mendez, Rizza Mae
Reyes, Sherilyn Lovely
Tamayo, Trisha
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