: 250
Carbohydrates are polyhydroxy aldehydes/ketones classified by size: monosaccharides (cannot be hydrolyzed — glucose, fructose, ribose), disaccharides (yield 2 monosaccharides — sucrose, maltose, lactose), polysaccharides (yield many monosaccharides — starch, cellulose, glycogen). By functional group: aldoses (-CHO: glucose, galactose, mannose) and ketoses (C=O: fructose). By carbon count: triose (C3), tetrose (C4), pentose (C5, ribose), hexose (C6, glucose/fructose). D/L designation based on highest-numbered chiral center (C5 for hexoses): OH right = D, OH left = L. All naturally occurring sugars are D-form. Cyclic structures: aldohexoses form pyranose (6-membered ring, glucose), ketohexoses form furanose (5-membered ring, fructose). Anomers differ at the anomeric carbon (C1 for aldoses, C2 for ketoses): alpha (OH axial in chair) vs beta (OH equatorial). Epimers differ at one specific chiral center: glucose/mannose are C2 epimers, glucose/galactose are C4 epimers. Reducing sugars have a free anomeric carbon (can open to free CHO): glucose, fructose (via enediol), maltose, lactose. Non-reducing: sucrose (both anomeric C locked in glycosidic bond). Key tests: Molisch (universal), Tollens/Fehling (reducing sugars), Seliwanoff (ketoses fast), Barfoed (monosaccharides fast vs disaccharides slow), iodine (starch = blue). This classification hierarchy is the framework for solving all JEE carbohydrate questions.