Carbohydrates

Carbohydrates

1. Functions

   • Energy Storage
   • Structural
   • Extenders of protein function
   • Informational Molecules

2. Monosaccharides: one sugar cannot be hydrolysed

   • Triose (3C)
     • Glyceraldehyde one chiral Carbon
     • Dihydroxyacetone no chiral Carbon
   • Tetrose (4C)
     • Aldotetrose two chiral carbons (diasteromers)
     • Ketotetrose one chiral carbon (enatiomers)
   • Pentose (5C)
     • Aldopentoses three chiral carbons (8 stereoisomers)
     • Keytopentose two chiral carbons (4 stereoisomers)
   • Hexose (6C)
     • Aldohexoses four chiral carbons (16 stereoisomers)
     • Keytohexose three chiral carbons (8 stereoisomers)

3. Disaccharides: 2 monosachharides joined by a glycosidic bond

   • Maltose
     • 2 D-Glucose joined by glycosidic bond
     • Major component of glycogen
     • Bond linking 2 glucose units is called alpha 1-4 glycosidic bond
   • Lactose
     • Insoluble and occurs naturally in milk
     • Beta 1-4 glycosidic bond
     • Composed of D- galactose and D-glucose
   • Sucrose
     • Main component of table sugar
     • Composed of glucose and fructose
     • Glycosidic bond is between C1 of glucose and C2 of fuctose. It is different to maltose and lactose as anomeric carbon atoms are involved in bond formation and no alpha beta isomers

4. Polysaccharides

   • Homopolysaccharides: only single type of monosaccharide
     • Starch 'energy storage of plants'
       • Amylose: water soluble, linear, linked at 1-4 C
       • Amylopectin: insoluble, linear at 1-4 C, branched at 1-6 C
     • Glycogen 'main storage of polysaccharides of animal cells'
       • 1-4 C linear
       • 1-6 C branched
     • Cellulose
       • linear consisting of glucose
       • Difference with amylose is the 1-4 linkages are B1-4 linkages which give rise to extended chains opposed to loose helices
       • Parallel chains are linked by hydrogen bonds which makes it strong
   • Heteropolysaccharides: two or more monosachharides and can be branched or unbranched
     • Peptidoglycans
       • Peptide linked polysaccharides in the cell wall of bacteria
     • Proteoglycans
       • glycosaminoglycans (GAGS) covalently linked to core proteins
     • Glycoproteins
       • Protein linked polysaccharides

5. A compound with three or more carbon atoms which has an aldehyde or keytone functional group and two or more functional groups