Biochemistry-Ch 11. Carbohydrates

阮雪芬NTUT

Nov 4, 2002

Monosaccharides

The simplest carbohydrates (C-H2O)n

Carbon hydrate

enantiomers

Trioses

D-Aldoses Containing Three, Four, Five, and Six Carbon Atoms

D-Aldoses Containing Three, Four, Five, and Six Carbon Atoms

D-Aldoses Containing Three, Four, Five, and Six Carbon Atoms

D-Aldoses Containing Three, Four, Five, and Six Carbon Atoms

D-Aldoses Containing Three, Four, Five, and Six Carbon Atoms

D-Ketoses Containing Three, Four, Five, and Six Carbon Atoms

D-Ketoses 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.

12

3

Envelop Conformations of -D-ribose

Four atoms are nearly coplanar and the fifth is about 0.5Å away from this plane.

4

5

1

23

4

5

O-glycosidic bond and N-glycosidic bond

NR2: N-glycosidic bond

Modified Monosaccharides

Modified Monosaccharides

Modified Monosaccharides

Modified Monosaccharides

Maltose, a disaccharide

Common Disaccharides (1)

glucose fructoseSucrase

Common Disaccharides (2)

Lactase: in human beings-galactosidase: in bacteria

galactose glucose

Common Disaccharides (3)

glucose glucoseMaltase

Electron Micrograph of a Microvillus

Polysaccharides

Large polymeric oligosaccharides Play vital roles in energy storage and in maintainin

g the structural integrity of an organism. If allof the monosaccharides are the same,these p

olymers 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

Repeating units in Glycosaminoglycans

Repeating units in Glycosaminoglycans

Repeating units in Glycosaminoglycans

Repeating units in Glycosaminoglycans