Oligosaccarides and Polysaccharides

1
Oligosaccarides and Polysaccharides

• Complex
• Carbohydrates

2
Lactose, a disaccharide

• a reducing sugar exhibits mutarotation
• 1,4-acetal linkage between 2 monomeric sugars
• acidic hydrolysis yields galactose and glucose
  (11).

3
Maltose, a disaccharide

• a reducing sugar mutarotates
• acidic hydrolysis yields only glucose
• can be digested by humans fermented by yeast.

4
Cellobiose, a disaccharide

• a reducing sugar mutarotates
• can NOT be digested by humans nor fermented by
  yeast CAN be digested by bacteria in ruminants
  and termites (which have ?-glucosidase enzyme).

5
Sucrose, a disaccharide

• NOT a reducing sugar NOT a hemiacetal
  does NOT
  undergo mutarotation
• hydrolysis yields glucose plus fructose (called
  invert sugar because rotation of polarized
  light changes sign).

6
Cellulose, a polysaccharide

• acid hydrolysis yields only glucose
• can have thousands of monomers linked only one
  anomeric carbon mutarotation occurs, NOT
  observed
• rigid structure hydrolyzed by ?-glucosidase
  enzymes.

7
Starch a mixture of linear and branched
polysaccharides

• energy storage for plants (potatoes)
• hydrolyzed readily by humans yields only glucose.

8
Starch the branched component

• a much larger and more highly branched
  polysaccharide (GLYCOGEN) provides energy storage
  in animals.

9
Ethanol production

• Ethanol can be produced by fermentation of simple
  sugars promoted by yeast.
• Corn and other grains are major sources of
  simple sugars, but much more carbohydrate-containi
  ng biomass is in the form of polysaccharides such
  as cellulose.

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Ethanol production

• Efforts are now underway to utilize the otherwise
  wasted (as a fuel source) polysaccharides by
  hydrolyzing them to their component
  monosaccharides followed by fermentation.
• Other plant sources of both simple and complex
  carbohydrates are being investigated as possible
  sources of ethanol for fuel.
• These include switchgrass, sugar cane, and even
  kudzu.

11
Other important carbohydrates
12
Cell-Surface Carbohydrates Blood Typing

• The surface of human blood cells has proteins
  covalently bound via glycoside bonds to
  oligosaccharides that serve as antigens.
• For a human to accept blood from a donor, their
  blood types must be compatible otherwise,
  agglutination (clotting) occurs.
• Compatibility depends on the identity of the
  sugars in the oligosaccharides bound to the
  surface proteins.

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Type A Blood
14
Type B Blood
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Type O Blood
Recent research has led to isolation of a
bacterial enzyme that cleaves the sugar bonded
to the 3-position of galactose in type A and B
peptides to make O-type