Study Guide for Test II

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Study Guide for Test II

• Chapter 6 pp159-196
• Chapter 7 pp203-221
• Chapter 8 pp243-288
• Chapter 9 pp 293-307

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Carbohydrates

• Most abundant biomolecules on Earth.
• Part of the diet in most of parts of the World.
• Oxidation of carbohydrates is the central
  energy-yielding pathway in non-photosynthetic
  cells.
• Insoluble carbohydrate polymers serve as a
  structural and protective elements in bacteria,
  plants and in connective tissue of animals.
• Participate in recognition and adhesion between
  cells.
• Complex carbohydrates attached to proteins and
  lipids participate in signaling.

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Carbohydrates

• Monosaccharides-simple sugars single polyhydroxy
  aldehyde or ketone unit.
• Oligosaccharides-short chains of monosaccharides
  joined by glycosidic bonds.
• Polysaccharides-sugar polymers of more then 20
  monosaccharides.

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Monosaccharides have chiral centers.

• By convention they are designated D-isomer and
  L-isomer.
• Molecules with n chiral centers can have 2n
  stereoisomers.
• Stereoisomers of monosaccharides of each carbon
  chain length can be divided in to two groups
  which differ in configuration about the chiral
  center of the MOST DISTANT carbon from the
  carbonyl carbon.
• Those with configuration at that carbon similar
  to D-glutaraldehyde are called D- and those
  similar to L-glutaraldehyde called, L-().

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Carbohydrate nomenclature cont.

• When the OH group of the carbon in question is
• on the right D-isomer
• on the left L-isomer
• Of 16 possible aldohexoses 8 of D-form and 8 of
  L-form.
• Most of the hexoses found in nature are of D-
  form.

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Two sugars that differ in the configuration of
one carbon atom are called epimers.
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Monosaccharides have cyclical structures.
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Pyranoses and Furanoses
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Chair forms of Pyranoses
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Hexose derivatives important in biology
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Polysaccharides

• Disaccharides and polysaccharides have a reducing
  end, free anomeric carbon (carbon not involved in
  a glycosidic bond).
• Homopolysaccharides-made up from the same
  subunit.
• Heteropolysaccharides-made up of different
  subunits

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Polysaccharides
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