Ch-2 | L-3 | Polysaccharides, qualitative test and biological role of Carbohydrates | D.Pharm 2nd yr

#carbohydrates #polysaccharides #qualitativetestforcarbohydrates #biologicalroleofcarbohydrates Notes, PYQ, MCQ, EXIT Exam Preparation, Pharmacist exam prepartion availbale in "MIND NURTURE" app Link for app: https://play.google.com/store/apps/de... Chemical Nature of Starch and Glycogen 1. Chemical Nature of Starch • Starch is a homopolysaccharide made up of α-D-glucose units. • It contains two polymers: o Amylose – linear/unbranched. o Amylopectin – branched. • General formula: (C₆H₁₀O₅)ₙ. • Glucose units are mainly joined by α-1,4 glycosidic bonds, while α-1,6 bonds occur at branching points. Amylose • About 15–20% of starch. • Long, unbranched chain of about 200–1000 glucose units. • Has α-1,4 linkages and forms a helical structure. • It is the water-soluble component. Amylopectin • Major branched component of starch. • Contains α-1,4 linkages in chains and α-1,6 linkages at branches. • Branching occurs approximately every 24–30 glucose residues. Properties of starch • White, tasteless and odourless powder. • Insoluble in cold water but forms a colloidal starch paste in hot water. • Gives a blue/blue-black colour with iodine. 2. Chemical Nature of Glycogen • Glycogen is a homopolysaccharide of α-D-glucose and is the main carbohydrate storage form in animals and fungi. • It is stored particularly in the liver and muscles and is built around a protein core called glycogenin. • Formula: (C₆H₁₀O₅)ₙ. • It is highly branched, with α-1,4 bonds forming chains and α-1,6 bonds forming branches. • Branches occur every 8–12 glucose units, making glycogen more highly branched than amylopectin. • Its compact, tree-like structure allows rapid mobilization of glucose. • Glycogen is white, amorphous, tasteless and water-soluble. It is more soluble than starch and gives a reddish-brown colour with iodine. 3. Biological Roles of Carbohydrates • Provide energy: 1 g carbohydrate = 4 kcal. • Stored as glycogen in animals and starch in plants. • Provide structural materials such as cellulose and chitin. • Have a protein-sparing action. • Help in fat metabolism and prevent excessive ketone-body formation. • Ribose and deoxyribose are components of RNA and DNA. • Glycoproteins and glycolipids participate in cell recognition and communication. • Mucopolysaccharides provide lubrication and protection. • Dietary fibre supports bowel movement and helps reduce cholesterol. 4. Important Qualitative Tests • Molisch's test: Purple/violet ring → confirms carbohydrates. • Benedict's test: Green, yellow, orange or brick-red precipitate → reducing sugar. • Barfoed's test: Red precipitate within 2–3 minutes → monosaccharide. • Seliwanoff's test: Cherry-red colour → ketose sugar such as fructose. • Iodine test: Blue-black → starch; reddish-brown → glycogen/dextrins. • Bial's test: Blue-green colour → pentose sugars. • Non-reducing sugar test: Hydrolysis followed by Benedict's test identifies sugars such as sucrose. 5. Sequence for Identifying an Unknown Carbohydrate Molisch → Iodine → Benedict → Barfoed → Seliwanoff → Hydrolysis + Benedict's test. #Starch #Glycogen #Polysaccharides #Carbohydrates #ChemicalNatureOfStarch #ChemicalNatureOfGlycogen #Amylose #Amylopectin #QualitativeTests #MolischTest #BenedictsTest #BarfoedsTest #SeliwanoffTest #IodineTest #BialsTest #ReducingSugars #CarbohydrateChemistry #PharmaceuticalChemistry #DPharm #PharmacyStudents