disaccharides + alcohol aldehyde hemi-acetal unstable + + H2O condensation

disaccharides D-lactose condensation -D-galactose -D-glucose HO CH2OH CH2OH 4 HO OH HO 1 2 HO 1 OH OH 3 OH -D-galactose -D-glucose C1 galactose + C4 of glucose D-glucose D-galactose glycoside bond - 1,4

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

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

Reducing disaccharides  4 1 1   2 - 1,4- glycoside ,  - 1,2- glycoside 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

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

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

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

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