Four important roles in living organisms:
1) provide energy through their oxidation
2) serve as stored form of energy
3) supply carbon for biosynthesis
4) form a part of the structural components of some cells and tissues
Anomeric carbon- original aldehyde of ketone carbon in non-ring form
Anomers- saccharides that differ in configuration only at the anomeric carbon
Epimers- saccharides that differ in configuration at only one carbon other than the anomeric
Mutarotation- change in specific rotation as anomers interchange via free aldehyde or ketone form in solution
Reducing sugars- yield positive Tollens, Benedict or Fehlings tests; must be hemiacetal or hemiketal
Hemiacetal- 1o ether/alcohol
Acetal- 1odi-ether
Hemiketal- 2o ether/alcohol
Ketal- 2o di-ether
Important Monosaccharides (reducing)
Glucose, aldohexose, blood sugar (dextrose)
Galactose, aldohexose , component of milk sugar, cerebrosides, blood antigens A & B
Fructose, ketohexose, fruit sugar (levulose)
Ribose, aldopentose, RNA component
2-Deoxyribose, aldopentose, DNA component lacks -OH at carbon # 2
Important Disaccharides
Cellobiose, [glucose-O-glucose -1,4] (from cellulose), reducing
Maltose, [glucose-O-glucose -1,4] (malting hops), reducing
Lactose, [galactose-O-glucose -1,4] (milk sugar), reducing
Sucrose, [glucose-O-fructose] , (table sugar), non-reducing
Important Polysaccharides
Cellulose ,glucose polymer, -glycosidic bond, plant structure
Amylose , glucose polymer, -glycosidic bond, plant starch
Amylopectin, glucose polymer, -glycosidic bond, cross linked every 20-30 units, plant starch
Glycogen, glucose polymer, -glycosidic bond, cross linked every 8-12 units, animal starch
Property................Mono- & di-saccharides....................... Polysaccharides
Molecular mass............................ low ....................................... high
Taste ........................................... sweet ......... ........................... tasteless
Soluble in water?......................... yes .......................................... no
Size ......................... small, can pass through membranes ........... large, cannot pass
Reducing? ................................ yes, except sucrose ..................... no
Mutarotation? ......................... yes, except sucrose ....................... no