Biochemistry- Ch 11. Carbohydrates 阮雪芬 NTUT Nov 4, 2002
Monosaccharides The simplest carbohydrates (C-H 2 O) n Carbon hydrate
enantiomers Trioses
D-Aldoses Containing Three, Four, Five, and Six Carbon Atoms
D-Ketoses Containing Three, Four, Five, and Six Carbon Atoms
Pyranose Formation
Furanose Formation
Ring Structures of Fructose : hydroxyl group attached to C-1 is below the plane of the ring. : hydroxyl group attached to C-1 is above the plane of the ring.
Conformation of Pyranose and Furanose Rings Pyranose and Furanose Rings are not planar.
Chair and Boat Forms of - D - glucopyranose The chair form is more stable.
1 2 3 Envelop Conformations of - D -ribose Four atoms are nearly coplanar and the fifth is about 0.5Å away from this plane
O-glycosidic bond and N-glycosidic bond NR 2 : N-glycosidic bond
Modified Monosaccharides
Maltose, a disaccharide
Common Disaccharides (1) glucose fructose Sucrase
Common Disaccharides (2) Lactase: in human beings -galactosidase: in bacteria galactose glucose
Common Disaccharides (3) glucose Maltase
Electron Micrograph of a Microvillus
Polysaccharides Large polymeric oligosaccharides Play vital roles in energy storage and in maintaining the structural integrity of an organism. If allof the monosaccharides are the same,these polymers are called homopolymers. In animal cells: Glycogen In plants: Starch Amylose: the unbranched type Amylopectin: the branched type
Branch Point in Glycogen Once in 10 units (glycogen) Once in 30 units (starch)
Starch and Glycogen Starch:
Cellulose One of the most abundant organic compounds in the biosphere. The major structural polymer of plants Consists of linear chains of glucose units
Glycosaminoglycans A different kind of repeating polysaccharide is present on the animal cell surface and in the extracellular matrix. Many glycosaminoglycans are made of disaccharides repeating units containing a derivative of an amino sugar, either glucosamine or galactosamine
Repeating units in Glycosaminoglycans