Qualitative Tests for Carbohydrates PDF

 Carbohydrates which are called as saccharides are biological molecular compounds consisted of three elements which are carbon(C), hydrogen(H) and oxygen(O). The term generated from carbon and hydrate; though some also contain nitrogen, phosphorus, or sulfur. General formula of c...

 Carbohydrates which are called as saccharides are biological molecular compounds consisted of three elements which are carbon(C), hydrogen(H) and oxygen(O). The term generated from carbon and hydrate; though some also contain nitrogen, phosphorus, or sulfur. General formula of carbohydrate is Cn(H2O)n. Importance of Carbohydrates; Carbohydrates perform numerous roles in living organisms; 1. Carbohydrates are a major source of metabolic energy  Glycog en 2. They provide energy storage such as starch in plant and glycogen in animal. 3. Another role is structural supporting such as; cellulose in plants chitin in exoskeleton of arthropods and cell walls of fungi. 4. They are components of some important molecules such as DNA, ATP and RNA etc. 5. Carbohydrates are linked with proteins forming glycoproteins and with lipids as glycolipids---these molecules are one of the major components of plasma membranes. «unique fingerprint»  One classification method for carbohydrates is according to number of their monomers which are; monosaccharides, disaccharides, oligosaccharides and polysaccharides.  Monosaccharides are simple form which has a role as being building block. It can be classified as trioses, pentoses and hexoses according number of carbon. Pentoses and hexoses are found in form of cyclic or non-cyclic. Non-cyclic form gives information about groups in structure which are ketone and aldehydes. Besides, a monosaccaride which contains aldehyde in structure is named as aldoses whereas which contains ketone in structure is named as ketoses. A: Pentoses B: Hexoses  Two monossaccharides give condensation reaction meaning releasing of water molecule. By this reaction disaccharides are formed. Glycosidic linkage occurs in formation of disaccharides. Oligosaccharides contain 3-10 monomer units whereas polysaccharides contain more than 10 monomer units. Polysaccharides  Molisch’s Test: is used to detect that whether sample is carbohydrate or not. Working principle is this test that pentoses and hexoses are dehydrated with presence of sulfuric acid. Indicator gives purple color by forming ring. Iodine Test: is used to detect that sample is starch or not. The combination of starch and iodine is intensely blue-black Barfoed’s Test: is 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 Benedict’s Test: It is used to detect the presence of reducing sugars. Seliwanoff’s Test: is a chemical test which distinguishes between aldose and ketose sugars. Ketoses give a red color is formed rapidly. In Aldoses, a slower forming light pink is observed. s Test: is a chemical test for the presence of pentoses