1. Biomolecules Survey Part 1: Carbohydrates Lecture Supplement page 81 Sucrose

2. Why Should I Study This? All organisms utilize carbohydrates  important biomolecules Nutrition: “Carbos” are more than just starch and sugar Application of previous concepts: Functional groups Stereochemistry Other structural features } control biological properties Why is this topic important?

3. Origin of “Carbohydrate” Monosaccharide : Cannot be hydrolyzed into simpler sugars Glucose C 6 H 12 O 6 Fructose C 6 H 12 O 6 no change H 2 O, H 3 O + no change H 2 O, H 3 O + Hydrolysis : “Water breaking;” reaction with water, often in the presence of acid or base Sucrose C 12 H 22 O 11 H 2 O, H 3 O + glucose + fructose Cellulose C n H 2n O n H 2 O, H 3 O + many glucose Disaccharide : Saccharide composed of two simpler sugars Polysaccharide : Composed of many monosaccharides Starch C n H 2n O n H 2 O, H 3 O + many glucose

4. Origin of “Carbohydrate” Sugar general formula = C n H 2n O n Confirmation sucrose + H 2 SO 4 C + H 2 O (steam) dehydrating agent = C n (H 2 O) n = carbohydrate = “carbon hydrate” sucrose H 2 SO 4 steam carbon Movie file: sucrose_dehydration.mov

5. an aldohexose C 3 = triose C 4 = tetrose C 5 = pentose C 6 = hexose Monosaccharide Molecular Structure Chain of three to six carbons One aldehyde or ketone -ose = saccharide Example: Glucose, a C 6 aldehyde All common/ important monosaccharides have... aldehyde = aldose ketone = ketose Aldoses more common than ketoses All other carbons are alcohols H-C-OH or CH 2 OH

6. The (D) -Aldose Family The (D) -Aldotrioses One stereocenter  two enantiomers ( L )-(-)- glyceraldehyde ( D )-(+)- glyceraldehyde Stereochemical configuration D = OH above CH 2 OH on the right Configuration of most natural aldoses L -aldoses generally unimportant No correlation of D / L with +/- or with R / S

7. The (D) -Aldose Family Fischer Projections Emil Fischer Determined relative structure of (D) -aldoses Guessed (D) -glyceraldehyde = R configuration (confirmed by x-ray crystallography; 1950) Nobel Prize in Chemistry 1902 (D)-(+)- glyceraldehyde Vertical lines = broken wedges Horizontal lines = solid wedges Fischer projection

8. The (D) -Aldose Family The (D) -Aldotetroses Two stereocenters  four stereoisomers Two (D) and two (L) (D) -(-)-erythrose (D) -(-)-threose Not found in nature

9. The (D) -Aldose Family The (D) -Aldopentoses Three stereocenters  eight stereoisomers Four (D) and four (L) (D) -(-)-ribose in RNA (ribonucleic acid) in DNA (deoxyribonucleic acid) (D) -(-)-arabinose (D) -(-)-lyxose Rare in nature (D) -(+)-xylose

10. The (D) -Aldose Family The (D) -Aldohexoses Four stereocenters  16 stereoisomers  eight (D) and eight (L) (D) -(+)-allose not found in nature (D) -(+)-altrose (D) -(+)-glucose most abundant monosaccharide (D) -(+)-mannose

11. The (D) -Aldose Family The (D) -Aldohexoses Four stereocenters  16 stereoisomers  eight (D) and eight (L) (D) -(-)-gulose not found in nature (D) -(-)-idose (D) -(+)-galactose fairly common (D) -(+)-talose Must I memorize all of these structures? Most important aldoses: Glucose, ribose, galactose Learn by doing problems

12. Midterm 1 1 hour exam (in class on Friday, May 4) Will cover: –Intro & Review up through Carbohydrates (Mass Spectrometry and IR will not be on exam) Last name A-K in CS50 Last name L-Z in Franz 1260 Tools –Pen and/or pencil –Eraser –Model kit –No calculators or cell phone

13. How should I study? Review past “Exam 1”s on Hardinger’s website http://www.chem.ucla.edu/harding/index.html (on left frame, click “Ch14C” then in middle frame click “Current and Past Exam and Keys”) http://www.chem.ucla.edu/harding/index.html

14. Midterm Review Session (Problem Solving Session) Tues, 5/1 YH3069 from 7-9pm (Ray) Will go over past midterms, Thinkbook problems, Vollhardt problems, Klein problems, etc. (at Ray’s discretion)

15. Cyclic Monosaccharides Many acyclic monosaccharides in equilibrium with more stable cyclic isomers (D) -(+)-glucose  - D -glucopyranose  - D -glucopyranose Pyran OH axial Less stable configuration OH equatorial More stable configuration Example: Glucose

16. Cyclic Monosaccharides  and  : Anomeric Carbon Stereochemistry  - D -glucopyranose  - D -glucopyranose Was carbon of carbonyl in acyclic form Point of attachment to other monosaccharides If anomeric group = OH, stereochemistry shifts   If anomeric group = OR, stereochemistry fixed as  or  Anomeric carbon  = trans CH 2 OH, anomeric OH  = cis CH 2 OH, anomeric OH cis trans

17. Cyclic Monosaccharides Haworth Projections  - D -glucopyranose  - D -glucopyranose

18. Cyclic Monosaccharides Furanoses Which ribose OH becomes ribofuranose ether? X = OH:  - D -ribofuranose (RNA) X = H:  - D -2-deoxyribofuranose (DNA) anomeric carbon X = OH: D -ribose X = H: D -2-deoxyribose furan  furanose 1 2 3 4 5 1 23 4 5

19. Cyclic Monosaccharides Furanoses in DNA A short segment of the DNA double helix  or  ?

20. Disaccharides Disaccharide: A carbohydrate composed of two monosaccharides An acetal C-O-C-O-C A hemiacetal C-O-C-O-H Useful vocabulary: Two carbohydrates linked by an acetal functional group Other anomeric carbon = hemiacetal functional group Fixed  or   /  mixture

21. Disaccharides Carbohydrate Ring Numbering Anomeric carbon receives lowest number: Carbon 1 in aldoses Carbon 2 (rarely 3) in ketoses All other carbons numbered in order

22. Disaccharides Maltose 1,4’-  - D -glucopyranosyl- D -glucopyranose  /  mixture H 3 O + /H 2 O hydrolysis Starch H 3 O + /H 2 O hydrolysis 2 Glucopyranose Product of partial hydrolysis of starch Anomeric carbon has  -linkage; easily digested by mammals (we have enzymes that can split  linkages)

23. Disaccharides Lactose 1,4’-  - D -galactopyranosyl- D -glucopyranose Present in mammalian milk (up to 8 % by weight; varies with species) Readily digested by infant mammals; requires enzyme lactase Adults often less tolerant due to low levels of lactase Lactaid milk is pre-treated with lactase enzyme Lactose H 3 O + /H 2 O hydrolysis + Glucopyranose Galactopyranose

24. Disaccharides Sucrose 2,1’-  - D -fructofuranosyl-  - D -glucopyranoside Unusual structure: Anomeric carbon-O-anomeric carbon Easily digested by mammals:  -linkage at anomeric carbon Most common disaccharide in nature Produced only by plants such as sugar cane, sugar beets World production 2008: 158.8 x 10 9 kg (~5 x 10 13 sugar packets) Sucrose H 3 O + /H 2 O hydrolysis Glucopyranose Fructofuranose A ketose +

25. Polysaccharides Polysaccharide: Hydrolysis yields many monosaccharide molecules Most important are glucose polymers: Cellulose and starch

26. Polysaccharides Cellulose Linear 1,4'-  - D -glucopyranose polymer ~5,000 - 10,000 glucopyranose molecules per cellulose molecule – high molecular weight Repeating subunit: Glucopyranose Most abundant organic substance in nature Main function: Structural H 3 O + /H 2 O hydrolysis Many glucopyranose Not easily digested by mammals Wood is ~50% cellulose by weight Strength due to intermolecular hydrogen bonding Cellulose chains lie by side in bundles and twist together to form fibers

27. Polysaccharides Chitin Linear 1,4'-  - D -glucopyranose polymer Found in shells of crustaceans (crab, shrimp, lobster) and also insects Repeating subunit: N-Acetyl Glucosamine Major component: Glucosamine, which is used to treat symptoms of arthritis H 3 O + /H 2 O hydrolysis Many N-Acetyl Glucosamine units

28. Polysaccharides Amylose STARCH Two forms: Amylose, amylopectin Amylose 30% of starch Linear polymer containing 300 to 3,000 glucopyranose Amylopectin 70% of starch Branched polymer with a branch every 20-25 glucose units Containing 2,000 to 200,000 glucopyranose 1,4’-  - D -glucopyranose polymer Main function: Energy storage Hydrolysis yields glucopyranose Easily digested by mammals Helical shape (as opposed to cellulose tightly packed, linear structure) Water can penetrate into the helical coils (starch is water-soluble, while cellulose is not) GLYCOGEN Storage polysaccharide in animals Branching every 10 glucose units

29. Napoloen’s Buttons p. 82 Amylose, amylopectin, and glycogen all feature  linkages (which are readily digestible by mammals), but they differ in the extent of branching. Remember: glycolytic (sugar-cleaving) enzymes can clip off sugars only at the ends of chains. More branched chains are therefore metabolized at a faster rate than less branched chains, which is especially advantageous for animals, which need sudden spurts of energy.