CHAPTER 20: Carbohydrates General, Organic, & Biological Chemistry Janice Gorzynski Smith

1. CHAPTER 20: Carbohydrates General, Organic, & Biological Chemistry Janice Gorzynski Smith

2. CHAPTER 20: Carbohydrates • Learning Objectives: • Identify carbohydrates • Describe properties and types (monosaccharides to polysaccharides) • Draw Fischer projections of carbohydrates • Classify as D or L • ID multiple chiral center and draw enantiomers • Draw common monosaccharides: glucose, galactose, fructose • Draw cyclic monosaccharides & identify hemiacetal •  &  isomers • draw Haworth projections • Draw ketohexose • Reduction & oxidation of monosaccharides • Describe & draw disaccharides • Polysaccharides: types and structures • Describe blood types • CH 20 Homework: • End of Chapter problems: 30, 34, 36, 38, 40, 42, 46, 52, 56, 58, 62, 66, 68, 74, 76, 82, 84 Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

3. Carbohydrates Definition • Carbohydrates, called sugars and starches, are • polyhydroxy aldehydes or ketones, or compounds • that can be hydrolyzed to them. • The simplest carbohydrates are monosaccharides. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

4. Carbohydrates Monosaccharides Aldehyde monosaccharides are aldoses ketone monosaccharides are ketoses. generally have 3 to 6 C atomsin a chain with an aldehyde or ketoneending and many –OH groups. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

5. Carbohydrates Disaccharides Disaccharidesare composed of two mono-saccharide units joined together by forming an acetal. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

6. Carbohydrates Definition Polysaccharides are composed of three or more monosaccharide units joined together. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

7. Carbohydrates Monosaccharides • The simplest aldose is glyceraldehyde. • The simplest ketose is dihydroxyacetone. A monosaccharide is characterized by the number of C atoms in its chain: • A tetrose has 4 C’s. • A triose has 3 C’s. • A pentose has 5 C’s. • A hexose has 6 C’s. The terms are then combined with the words aldose and ketose: • Glyceraldehyde is an aldotriose. • Dihydroxyacetone is a ketotriose. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

8. Carbohydrates Monosaccharides • Monosaccharides are sweet tasting, but their • relative sweetness varies greatly. • They are polar compounds with high melting • points. • The presence of so many polar functional groups • capable of hydrogen bonding makes the • monosaccharides very water soluble. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

9. Carbohydrates Monosaccharides: Chirality • The prefix D is used when the –OH group is drawn • on the right side of the carbon chain. • The prefix L is used when the –OH group is drawn • on the left side of the carbon chain. • The wedged and dashed lines can be re-drawn in • a Fischer projection formula: Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

10. Carbohydrates Monosaccharides: Chirality Glucose has four chirality centers and is drawn as: Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

11. Carbohydrates D vs L Monosaccharides The configuration of the chirality center farthest from the carbonyl group determines whether a monosaccharide is D or L. All naturally occurring sugars are D sugars. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

12. Carbohydrates Common Monosaccharides • Glucose (dextrose) is blood sugar and the most abundant monosaccharide. • Normal blood glucose levels are 70-110 mg/dL. • Excess glucose is stored as the polysaccharide glycogen or as fat. • Fructose is one of the components of the disaccharide sucrose. • Galactose is one of the components of the disaccharide lactose. • Patients with galactosemia lack an enzyme needed to metabolize galactose, which accumulates and causes cataracts and cirrhosis. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

13. Carbohydrates Cyclic Monosaccharides When the aldehyde and alcohol are on the same molecule, a stable cyclic hemiacetal is formed: Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

14. Carbohydrates Cyclic Monosaccharides The C atom that is part of the hemiacetal is a new chirality center, called the anomer carbon. Haworth projections Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

15. Carbohydrates Mutarotation The cyclization reaction exists in an equilibriumcalled mutarotation. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

16. Carbohydrates Haworth Projections HOW TO Draw a Haworth Projection from an Acyclic Aldohexose Draw both anomers of D-mannose in a Haworth projection. Example

17. Carbohydrates Haworth Projections HOW TO Draw a Haworth Projection from an Acyclic Aldohexose Place the O atom in the upper right corner of a hexagon, and add the CH2OH group to the right of the O atom. Step [1]

18. Carbohydrates Haworth Projections HOW TO Draw a Haworth Projection from an Acyclic Aldohexose Place the anomeric C on the first C clock- wise from the O atom. Step [2]

19. Carbohydrates Haworth Projections HOW TO Draw a Haworth Projection from an Acyclic Aldohexose Add the other substituents to the remaining carbons, clockwise around the ring. Step [3]

20. Carbohydrates Cyclic Fructose Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

21. Carbohydrates Reduction of Monosaccharides The carbonyl group of an aldose is reduced to a 1o alcohol using H2 with Pd. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

22. Carbohydrates Oxidation of Aldoses • The aldehyde group is easily oxidized to a • carboxylic acid using Benedict’s reagent. • Aldoses can be oxized, while ketones cannot. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

23. Carbohydrates Disaccharides When acetal formation occurs between two mono- saccharides, the bond that joins them together is called a glycosidic linkage. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

24. Carbohydrates Disaccharides Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

25. Carbohydrates Hydrolysis of Disaccharides • Hydrolysis cleaves the C—O glycosidic linkage • and forms two monosaccharides. • Hydrolysis of maltose yields 2 glucose molecules. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

26. Carbohydrates Disaccharide Sweeteners Sucrose (table sugar) is a disaccharide consisting of 1 glucose ring and 1 fructose ring Artificial Sweeteners: Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

27. Carbohydrates Polysaccharides Cellulose makes up the insoluble fiber in our diets, which is important in adding bulk to waste to help eliminate it more easily. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

28. Carbohydrates Polysaccharides • Starch is a polymer made up of repeating glucose • units joined by alpha glycosodic linkages. • Starch is present in corn, rice, wheat, and potatoes. • The first main type of starch is amylose: Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

29. Carbohydrates Polysaccharides • The second type of starch is amylopectin. • Amylose is an unbranched polymer linked by 14-a-glycosidic linkages. • Amylopectin is a branched polymer linked by 14-a and 16-a-glycosidic linkages. • Both starch molecules can be digested by humans using the enzyme amylase. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

30. Carbohydrates Polysaccharides • Glycogen is the major form of polysaccharide • storage in animals, similar in structure to • amylopectin. • It is stored mainly in the liver and in muscle cells. • When glucose is needed for energy, glucose • units are hydrolyzed from the ends of the glycogen • polymer. • Because glycogen is highly branched, there • are many ends available for hydrolysis. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

31. Carbohydrates Polysaccharides Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

32. Carbohydrates Blood Type • There are four blood types—A, B, AB, and O. • Blood type is based on 3 or 4 monosaccharides • attached to a membrane protein of red blood cells. • Each blood type has the monosaccharides below: Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

33. Carbohydrates Blood Types • Type A blood contains a fourth monosaccharide: • Type B contains an additional D-galactose unit. • Type AB has both type A and type B carbohydrates. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

34. Carbohydrates Blood Types Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

35. Carbohydrates Blood Types Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

36. Carbohydrates Blood Types • The blood of one individual may contain antibodies • to another type. • Those with type O blood are called universal • donors, because people with any other blood type • have no antibodies to type O. • Those with type AB blood are universal recipients • because their blood contains no antibodies to • A, B, or O. Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.