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disaccharides

disaccharides. +. alcohol. aldehyde. hemi-acetal. unstable. +. + H 2 O. hemi-acetal. alcohol. acetal. stable. condensation. disaccharides.  - D - galactose  - D - glucose. condensation. D-lactose. HO. CH 2 OH. CH 2 OH. 4. HO. OH. HO. 1. 2. HO. OH. 1. OH. 3. OH.

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disaccharides

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  1. disaccharides + alcohol aldehyde hemi-acetal unstable + + H2O hemi-acetal alcohol acetal stable condensation

  2. disaccharides -D-galactose -D-glucose condensation D-lactose HO CH2OH CH2OH 4 HO OH HO 1 2 HO OH 1 OH 3 OH -D-galactose -D-glucose C1galactose + C4 of glucose D-glucose D-galactose - 1,4 glycoside bond

  3. O + H2O -D-galactose -D-glucose -1,4-glycoside lactose milk sugar can’t be absorbed by intestines hydrolyzed by enzyme lactase stable Is this a reducing sugar? acetal hemi-acetal unstable reducing sugar

  4. 1 2 3 4 5 6 O sucrose -D-glucose -D-fructose condensation CH2OH HO HO HO OH OH 6 4 -D-glucose OH CH2OH 3 - - 1,2- glycoside HO 2 5 sucrose 1 HOH2C - D-fructose

  5. Reducing disaccharides  4 1 1   2 - 1,4- glycoside glycoside ,  - 1,2- lactose sucrose lactose = head -to-tail sucrose = head -to-head one hemi-acetal no hemi-ketal reducing sugar non-reducing sugar all monosaccharides are reducing

  6. Polysaccharides 2 glucose molecules 1 -1,4-glycoside  4 maltose hemi-acetal homo-polysaccharide only glucose -1,4-linkages starch amylose 4,000 glucose

  7. Starches amylose helical -1,4-linkages alternating axial and equatorial 4000 glucose  4 amilopectin 1 24 - 30 glucose 6  “branching” -1,6-linkages 1 carbohydrate in animals glycogen smaller “chain” more highly branched

  8. Cellulose homo-polysaccharide of glucose -1,4 linkages 1 1 4  4 equatorial-equatorial linkages long, straight chains -1,4 linkages difficult to hydrolyze structural saccharides

  9. Cellulose H-bonds between adjacent chains form fibers cotton and flax are cellulose

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