Carbohydra tes : What do you need to know?

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

2. 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

3. 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

4. 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

5. 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)

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

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

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

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

11. 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

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

13. cyclic hemiacetalforms ofD-glucose:intramolecular reaction betweencarbonyl group&hydroxyl groupon carbon #5.

14. 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 beacrossD or L CH2OH group • will bebesideD or L CH2OH group

15. 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 • FischerHaworth • -OH on right = -OH down • -OHon left = -OH up

16. 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

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

18. Glycoside Formation • 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

19. 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