σακχαρων Greek “ sakcharon” = sugar

Carbohydrates – polyhydroxyaldehydes or polyhydroxy- ketones of formula (CH 2 O) n, or compounds that can be hydrolyzed to them. (aka sugars or saccharides) Monosaccharides – carbohydrates that cannot be hydrolyzed to simpler carbohydrates; eg. Glucose or fructose. Disaccharides – carbohydrates that can be hydrolyzed into two monosaccharide units; eg. Sucrose, which is hydrolyzed into glucose and fructose. Oligosaccharides – carbohydrates that can be hydrolyzed into a few monosaccharide units. Polysaccharides – carbohydrates that are are polymeric sugars; eg Starch or cellulose.

Aldose – polyhydroxyaldehyde, eg glucose Ketose – polyhydroxyketone, eg fructose Triose, tetrose, pentose, hexose, etc. – carbohydrates that contain three, four, five, six, etc. carbons per molecule (usually five or six); eg. Aldohexose, ketopentose, etc.

Reducing sugar – a carbohydrate that is oxidized by Tollen’s, Fehling’s or Benedict’s solution. Tollen’s: Ag +  Ag (silver mirror) Fehling’s or Benedict’s: Cu 3+ (blue)  Cu 2+ (red ppt) These are reactions of aldehydes and alpha-hydroxyketones. All monosaccharides (both aldoses and ketoses) and most * disaccharides are reducing sugars. * Sucrose (table sugar), a disaccharide, is not a reducing sugar.

Glucose (a monosaccharide) Plants: photosynthesis chlorophyll 6 CO H 2 O C 6 H 12 O O 2 sunlight (+)-glucose (+)-glucose starch or cellulose respiration C 6 H 12 O O 2 6 CO H 2 O + energy

Animals plant starch (+)-glucose (+)-glucoseglycogen glycogen(+)-glucose (+)-glucosefats or aminoacids respiration (+)-glucose + 6 O 2 6 CO H 2 O + energy

(+)-glucose? An aldohexose Emil Fischer (1902) Four chiral centers, 2 4 = 16 stereoisomers

Ruff degradation – a series of reactions that removes the reducing carbon ( C=O ) from a sugar and decreases the number of chiral centers by one; used to relate configuration.

Kiliani-Fischer synthesis. A series of reactions that extends the carbon chain in a carbohydrate by one carbon and one chiral center.

Epimers – stereoisomers that differ only in configuration about one chiral center.

Exists only in solution. There are two solids: α-glucose m 146 o [α] = β-glucose m 150 o [α] = In water each mutarotates to an equilibrium with [α] = (63.6% β / 36.4% α)

Addition of alcohols to aldehydes/ketones:

Disaccharides: (+)-maltose “malt sugar” two glucose units (alpha) (+)-cellobiose two glucose units (beta) (+)-lactose “milk sugar” galactose & glucose (+)-sucrose “table sugar” glucose & fructose

Polysaccharides starch cellulose Starch20% amylose (water soluble) 80% amylopectin (water insoluble) amylose + H 2 O  (+)-maltose (+)-maltose + H 2 O  (+)-glucose starch is a poly glucose (alpha-glucoside to C-4)

Amylopectin + H 2 O  (+)-maltose (+)-maltose + H 2 O  (+)-glucose Also a polyglucose, but branched every units:

Cellulose is a polyglucose with a beta-linkage: