Announcements & Agenda (04/11/07)

1. Announcements& Agenda(04/11/07) • New Extra Credit Assignment Due Monday • Pick Up Old Graded Stuff • Pick Up Flowchart if you were absent Monday • Quiz Friday (13.4, 13.5, & Ch 14) • Exam Fri 04/20 (Ch 13,14,15) • Will Post Practice Exam Soon! • Today • Finish Cyclic Monosaccharides • Reactions of carbohydrates • Disaccharides • Polysaccaharides

2. What sugar is this? • Mannose • Glucose • Fructose • Galactose

3. Is this the L- form or the D-form? • L • D • B

4. Which Structure is Correct? • A • B • C • D

5. Last Time: Formation of Cyclic Glucose Two “anomers” possible: a and b; this one is alpha b/c the –OH is opposite the -CH2OH group!

6. C H O H C H O H C H O H 2 2 2 H O O O O H O C O H O H O H H O H O H O H O H O H O H O H Mutarotation: Interconversion of Anomers • cyclic structures open and close. • -D-glucose converts to β-D-glucose & vice versa. • at any time, only a small amount of open chain forms. -D-glucose D-glucose (open) β-D-glucose (36%) (trace) (64%)

7. C H O H 2 C H O H C H O H C H O H O H 2 2 O O C O 2 H O C H O H O H H C O H O H C H O H 2 H C O H O H O H C H O H 2 Cyclic Structure of Fructose • is a ketohexose. • reacts the -OH on C-5 with the C=O on C-2 α-D-fructose D-fructose -D-fructose -OH from C5 attaches to C from C=O!

8. Chemical Properties of Monosaccharides (14.4)

9. Reducing Sugars • are monosaccharides that oxidize to give a carboxylic acid. • undergo reaction in the Benedict’s test. • include the monosaccharides glucose, galactose, and fructose. • many disaccharides can also oxidize • but only if one monosaccharide can ring open! (see later slides)

10. Oxidation of D-Glucose [O] QUESTION: WHY CAN FRUCTOSE (A KETONE) BE OXIDIZED??? ANSWER: ISOMERIZATION TO AN ALDEHYDE…

11. One Test for Glucose in Urine:Benedict’s Test

12. Reduction of Monosaccharides • involves the carbonyl group. • produces sugar alcohols, or alditols. • such as D-glucose gives D-glucitol also called sorbitol. D-Glucitol

13. Learning Check Write the products of the oxidation and reduction of D-mannose. D-mannose

14. Solution D-mannitol D-mannose D-mannonic acid

15. Disaccharides (14.5)

16. Important Disaccharides: Know These 3 A disaccharideconsists of two monosaccharides. Monosaccharides Disaccharide glucose + glucose maltose + H2O glucose + galactose lactose + H2O glucose + fructose sucrose + H2O

17. Maltose • A.K.A. “malt sugar” • obtained from starch hydrolysis • used in cereals, candies, and brewing • linked by an -1,4-glycosidicbond formed from the  −OH on C1 of the 1st glucose and −OH on C4 of the 2nd glucose • found in both the - and β - forms Free α-OH

18. Lactose • a disaccharide of β-D-galactose and α- orβ-D-glucose. • contains a β -1,4-glycosidic bond. • is found in milk and milk products. α-form α-form

19. Sucrose Sucrose or table sugar • is obtained from sugar cane and sugar beets. • consists of α-D-glucose and β-D-fructose. • has an α,β-1,2-glycosidic bond. α-D-glucose β-D-fructose Is a non-reducing sugar. Why?

20. Learning Check Write the structures of the two monosaccharides that form when sucrose is hydrolyzed.

21. Solution

22. Polysaccharides • often polymers of D-glucose. • include amylose & amylopectin, starches made of α-D-glucose. • include glycogen (animal starch in muscle), which is made of α-D-glucose. • include cellulose (plants and wood), which is made of β-D-glucose. α-D-Glucose

23. Starch: Structures of Amylose & Amylopectin

24. Amylose • a polymer of α-D-glucose molecules. • linked by -1,4 glycosidic bonds. • a continuous (unbranched) chain.

25. Amylopectin • also a polymer of α-D-glucose molecules. • is a branched-chain polysaccharide. • has α-1,4-glycosidic bonds between the glucose units. • has α-1,6 bonds to branches.

26. Glycogen • is the polysaccharide that stores α-D-glucose in muscle. • is similar to amylopectin, but is more highly branched.

27. Cellulose • a polysaccharide of glucose units in unbranched chains. • has β-1,4-glycosidic bonds. • cannot be digested by humans because humans cannot break down β-1,4-glycosidic bonds.

28. Learning Check Identify the polysaccharides and types of glycosidic bonds in each of the following. A. B. C.

29. Solution A. Cellulose -1,4-glycosidic bonds B. Amylose -1,4-glycosidic bonds Amylopectin -1,4-and -1,6-glycosidic bonds C. Glycogen -1,4-and -1,6-glycosidic bonds (more branched than amylopectin)

30. 0 Other cool sugars… • Chitin (glucose w/ amide) = insect exoskeleton. • Similar to that in bacterial cell wall; makes bacterial cells hard to break open. Lysozyme – defense protein to break down cell walls • Cell surface, including ABO blood groups.

31. You are responsible for the Health Note on Page 485!

32. More Interesting Info: Sweetness of Sweeteners • Sugars differ in sweetness. • are compared to sucrose (table sugar), which is assigned a value of 100. 60 000

33. History of Artificial Sweeteners • Saccharin: http://en.wikipedia.org/wiki/Saccharin • 1879 Ira Remsen and Constantin Fahlberg at JHU • Monsanto Chemical Company in Saint Louis became profitable in manufacturing and selling saccharin. • Aspartame (Nutrasweet) was originally patented by GD Searle in Chicago. 1985 Monsanto bought GD Searle and created the NutraSweet Company. • Neotame (an analog of Aspartame) is 5 times sweeter than Aspartame. See http://www.neotame.com/

34. Chapter 15: Lipids… mmm…Fat… 15.1 Lipids 15.2 Fatty Acids