Methods of Carbohydrate Detection Flashcards
Is Molisch’s Test quantitative or qualitative?
Qualitative
State the principle of Molisch’s Test.
Reaction of CHO with H2SO4 occurs. Glycosidic bonds in polysaccharides are broken to form monosaccharides. A dehydration reaction and formation of furfural occurs. The reaction of furfural with a phenolic compound (alpha-naphthol) produces a purple or violet condensation product
True or false: the Anthrone Test is qualitative.
False
What is the principle and procedure of the Anthrone Test?
Similar to Molisch’s test, but the phenolic compound in this instance is anthrone, and quantitative determination can be obtained using the spectrophotometer. A positive result will produce a blue-green complex that absorbs at 620nm, and the intensity indicates the quantity. Standards are required for this method.
Fehling’s Test examines for ________ sugars.
Reducing
What colour is the precipitate of a positive Fehling’s test?
Brick-red
Benedict’s Test and Barfoed’s Test are _______ tests.
Qualitative
The Nelson-Somogyi Assay is a _______ test.
Quantitative
What test can be used to detect starch, and other polysaccharides?
Iodine test
What is the principle of the Nelson-Somogyi Assay?
Cu2+ ions are reduced to Cu+ by reducing sugars. Further reaction occurs. Cu+ ions are reacted with a mixture of acidic ammonium molybdate and sodium arsenate (an arsenomolybdate complex).
This results in a blue solution, absorbing at 520nm.
What results should be observed when the iodine test is performed on suspected amylose, amylopectin, and glycogen?
Amylose - incorporation of I3- ions into long amylose helix forms a blue black colour
Amylopectin - no reaction, and forms a yellow colour
Glycogen - does not fully incorporate, and forms a reddish-brown colour
True or false: aldehyde groups are unable to participate in redox reactions.
False
Reducing sugars have a free ______ group.
Aldehyde
