Carbohydrates: What do you need to know? Characteristics of Carbohydrates Structural & functional Chirality & Isomerism Fischer projections Stereoisomers: Enantiomers vs. Diastereomers Monosaccharides Important ones to know (trioses-hexoses) Haworth projections Reactions Disaccharides Polysaccharides Characterisitics & types Biological Issues Cells Diet

Carbohydrates Carbo (carbon) hydrate (water) - Cn(H2O)n Carbohydrates are produced in plants through Photosynthesis CO2 + H2O + --> carbohydrates + O2 cellulose (structural components) starch (energy reserve) Carbs in Humans Carbohydrate oxidation --> chemical & heat energy Carbohydrate storage = glycogen (energy reserve) Carbohydrates provide C atoms for synthesis of proteins, nucleic acids & lipids Carbohydrates are important in structure of DNA & RNA Carbohydrates can be linked with lipids & proteins

Types of Carbohydrates All carbohydrates are polyhydroxy aldehydes (PA - ex: glucose) or ketones (PK - ex: fructose) or compounds that hydrolyze to produce them. Monosaccharides Composed of ONE PA or PK unit Monomers for larger carbohydrates that are formed by condensation reactions Simplest- Trioses: 2,3-dihydroxypropanal & dihydroxypropanone Disaccharides - 2 monomer units Oligosaccharides Composed of 3 - 10 monosaccharide units Humans can’t digest most of these; bacteria in colon do (producing large quantities of CO2 gas) Polysaccharides Composed of “many” monosaccharide units aldohexose ketohexose

Dietary Carbs Dietary Carbs: glucose (m), fructose (m), sucrose (d), starch (p) Simple (sugars) vs. Complex (starch) eat less eat more relatively pure obtained from nutrient rich foods quickly digested gradually digested 1900 vs. 2000 cal = 2 starch : 1 sugar cal = 1 starch : 1 sugar commercial food = 25% sugar eaten commercial food = 70% sugar eaten

Monosaccharides Most common in nature have 3-7 C atoms Trioses - Heptoses Aldoses vs. Ketoses Sugars - many are sweet-tasting Stereoisomers Nearly all naturally occurring are D L isomers cannot be used by the body. # of isomers/aldose - dependent on # of chiral centers # of isomers/ketose - 1/2 the number possible for aldoses (= # of C atoms)

Fischer projections and common names for D-aldoses three, four, five, and six carbon atoms.

Fischer projections and common names for ketoses containing three, four, five, and six carbon atoms.

SIX biochemically important monosaccharides All are D enantiomers Two Trioses One pentose Three hexoses Know their structures!!

Trioses D-glyceraldehyde Dihydroxyacetone Intermediate in glycolysis 2,3-dihydroxypropanal Intermediate in glycolysis Chiral molecule Dihydroxyacetone Dihyroxypropanone Intermediate in glycolysis Achiral molecule

Pentose D-ribose An important component of nucleic acids Found in energy rich compounds (ie. ATP) D-ribose: in RNA 2-deoxy-D-ribose: in DNA

Cyclic Monosaccharides Common in pentoses & hexoses Open chain <==> cyclic Method of cyclization Carbonyl group reacts with hydroxyl group Hemiacetal formation Ring to Chain conversion

cyclic hemiacetal forms of D-glucose: intramolecular reaction between carbonyl group & hydroxyl group on carbon #5.

Haworth projection formulas: Cyclic monosaccharide Count C # clockwise from O atom in ring Highest # C shows D or L form (D form sticks up from the ring) Alpha or beta shown by #1C’s -OH group  will be across D or L CH2OH group  will be beside D or L CH2OH group

Haworth Projection Formulas Specifications D vs. L: determined by position of terminal CH2OH group Up = “D” Down = “L” determined by position of -OH on C#1 relative to CH2OH opposite directions : both same direction If  &  doesn’t matter, attach -OH with wavy line Specific identification of compound is determined by positions of other -OH groups Fischer Haworth -OH on right = -OH down -OH on left = -OH up

Reactions of Monosaccharides Oxidation (product is acidic sugar) Aldose --> aldonic acid Weak oxidizing agent (ex.:Fehling’s or Tollens) causes oxidation at the aldehyde end Ketoses turn into aldoses due to basic solution Aldose --> aldaric acid Strong oxidizing agent causes oxidation at both ends Aldose --> alduronic acid Enzymes at certain lab conditions can cause oxidation at the 1˚ alcohol end only The glucose content of urine can be determined by dipping a plastic strip treated with oxidizing agents. Blue Benedict’s solution makes a red precipitate when reducing sugar (glucose) reacts

Reactions of Monosaccharides Reduction (product is sugar alcohol) Reaction takes place at the carbonyl group

Glycoside Formation Cyclic Aldose/ketose + alcohol --> glycoside Remember: hemiacetal + alcohol --> acetal Acetals have two –OR groups attached to same C atom Cyclic Aldose/ketose + alcohol --> glycoside (monosaccharide acetal) Naming: Indicate  or  form List alkyl or aryl group on O Then monosaccharide name Finally add -ide suffix

Giant Hogweed (Heracleum mantegazzianum) Native to Caucasus Mountains in Asia A problem weed recently found in Oregon. Clear, watery sap contains a glucoside, which causes phyto-dermatitis. Skin contact with sap, then exposure to sunlight produces painful, burning blisters which may develop into purplish or blackened scars Giant Hogweed (Heracleum mantegazzianum) Background: Giant hogweed grows as a native in the Caucasus Mountains, a region of Asia between the Black and Caspian seas. Planted as a curiosity in arboretums and private gardens in Europe and North America early in the twentieth century, soon escaped and naturalized in surrounding areas, especially riparian and urban sites. It is reported to be a problem weed in Europe, England, Scotland, Scandinavia and Germany. In North America it grows in Ontario, British Columbia, Maine, Maryland, New York, Washington and now in Oregon. Giant hogweed constitutes a public health hazard. Its clear, watery sap contains a glucoside, which causes phyto-dermatitis. Skin contact with sap followed by exposure to sunlight can produce painful, burning blisters that may develop into purplish or blackened scars. Identification: Giant hogweed is a member of the carrot or parsley family and its most impressive characteristic is its massive size. It looks very similar to cow parsnip, which is a common native plant in the northwest and grows in riparian areas and roadsides.