8 Questions
Which test can differentiate between monosaccharides and disaccharides based on the speed of the reaction?
Barfoed's Test
What is indicated by the formation of a silver mirror or a reddish-brown precipitate in a test?
Presence of ketoses
Which test shows a positive result by changing color to green, yellow, orange, or brick-red?
Barfoed's Test
Which test is used to detect the presence of all types of carbohydrates by observing the formation of a violet ring?
Molisch Test
What distinguishes ketoses from aldoses in the Seliwanoff's Test?
Cherry-red color formation
Which crystals formed are described as a 'bundle of hay'?
Glucosazone crystals
What does a positive result in the Iodine Test indicate?
Presence of starch
Which test helps in identifying reducing sugars by observing crystalline derivatives under a microscope?
Osazone Formation
Study Notes
Carbohydrate Tests
- Benedict's Test detects reducing sugars, indicated by a color change from blue to green, yellow, orange, or brick-red, depending on the concentration of reducing sugars.
Detection of Monosaccharides and Disaccharides
- Barfoed's Test differentiates between monosaccharides and disaccharides, with monosaccharides giving a positive result (reddish-brown precipitate) faster than disaccharides.
Aldoses and Ketoses
- Seliwanoff's Test differentiates between aldoses and ketoses, with positive results for ketoses showing a rapid formation of a cherry-red color.
Starch Detection
- Iodine Test detects the presence of starch, indicated by a change from yellow-brown to blue-black in the presence of starch.
Reducing Sugars
- Tollen's Test identifies reducing sugars, indicated by the formation of a silver mirror or a reddish-brown precipitate.
Carbohydrate Detection
- Molisch Test detects the presence of all types of carbohydrates, indicated by the formation of a violet ring at the interface of the two liquids.
Osazone Formation
- Osazone Formation (Phenylhydrazine Test) identifies reducing sugars, observed by the formation of osazones (crystalline derivatives) under a microscope.
- Glucosazone crystals, formed by glucose, are often described as a "bundle of hay".
- Lactosazone crystals, formed by lactose, are described as a "powder puff".
This quiz covers the principles and results of three common laboratory tests for carbohydrates: Benedict's test for reducing sugars, Barfoed's test for differentiating between monosaccharides and disaccharides, and Seliwanoff's test for distinguishing between aldoses and ketoses.
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