Announcements & Agenda (04/16/07)

1. Announcements& Agenda(04/16/07) • Pick up Quizzes • Extra Credit Assignment Due NOW! • Exam Fri 04/20 (Ch 13,14,15) • REVIEW @ 5 pm Wed!!! • exam will not include pp. 520-524 • BTW, “Forms of Carbohydrates” tutorial on CD good for looking at carbohydrate structures • Today • Finish fatty acids (15.2) • Triglycerides & reactions (15.3, 15.4) • Glycerophospholipids (15.5) • Cholesterol (15.6)

2. Last Time: 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

3. The monosacharides in glycogen in are linked by… • a-1, 4 glycosidic bonds only • b-1, 4 glycosidic bonds only • a-1, 6 glycosidic bonds only • Contain both a and b glycosidic bonds • None of the above

4. Last Time: Intro to Lipids (Fat!)

5. 24 Good Practice Problems (Ch 15) 15.05, 15.11, 15.13, 15.19, 15.21, 15.27, 15.29, 15.31, 15.37, 15.39, 15.41, 15.43, 15.45, 15.49, 15.51, 15.57, 15.65, 15.67, 15.69, 15.71, 15.73, 15.77, 15.78, 15.81 Turn in your work for 15 of these by Wed @ 11 am to receive 1 pt extra credit

6. Last Time: Lipids w/ Fatty Acids • saturated: all single C–C bonds. • unsaturated:with one or more double C=C bonds.

7. Last Time: Unsaturated vs. Saturated Fatty Acids • Unsaturated: contain one or more cis double C=C bonds. • have “kinks” in the fatty acid chains. • do not pack as closely. • have fewer attractions between chains. • have lower melting points. • are liquids at room temperature. “kinks” in chain

8. 15.3 Waxes, Fats, and Oils

9. Waxes • esters of saturated fatty acids and long-chain alcohols. • coatings that prevent loss of water by leaves of plants.

10. Fats and Oils: Triacylglycerols • also called triacylglycerols or triglycerides • esters of glycerol. • produced by esterification. • Formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids.

11. Formation of a Triacylglycerol glycerol + three fatty acids triacylglycerol + + 3H2O

12. Different Fatty Acids Can Make Up Triacylglycerols! Stearic acid Oleic acid Myristic acid

13. Melting Points of Fats and Oils A fat • is solid at room temperature. • is prevalent in meats, whole milk, butter, and cheese. (mmm… cheese) An oil • is liquid at room temperature. • is prevalent in plants such as olive and safflower.

14. Oils w/ Unsaturated Fatty Acids • have more unsaturated fats • have cis double bonds that cause “kinks” in the fatty acid chains • “kinks” result in poor packing • have lower melting points than saturated fatty acids. • are liquids at room temperature.

15. Diagram of Triacylglycerol with Unsaturated Fatty Acids Unsaturated fatty acid chains with kinks cannot pack closely.

16. Percent Saturated and Unsaturated Fatty Acids In Fats and Oils

17. 15.4 Chemical Properties of Triacylglycerols The chemical reactions of triacylglycerols are similar to those of alkenes and esters. • Hydrogenation of double bonds in unsaturated fatty acids by H2 (compare to alkenes). • Hydrolysis of ester bonds by water in the presence of an acid, a base, or an enzyme (compare to esters).

18. Hydrogenation of Oils • adds H2 to the carbon atoms of double bonds. • increases the melting point. • produces solids such as margarine and shortening.

19. Hydrogenation + 3H2 Ni glyceryl tripalmitoleate (tripalmitolean) glyceryl tripalmitate (tripalmitin)

20. Olestra, A Fat Substitute • used in foods as an artificial fat. • sucrose linked by ester bonds to several long-chain fatty chains. • not broken down in the intestinal tract.

21. Olestra (WOW or Light) • http://en.wikipedia.org/wiki/Olestra • Launched in 1996 as WOW potato chips ($400 mil in 1998). Fell to $200 mil when FDA restricted the label to state “may cause abdominal cramping and loose stools”. It also inhibited absorption of Vitamins A, D, E and K • It is made from one sucrose and 8 oleic acid molecules. The molecule is so large that it could not migrate past the intestinal wall

22. Cis and Trans Fatty Acids Unsaturated fatty acids can be • cis with bulky groups on same side of C=C. CH3─ (CH2)5(CH2)7─COOH cis C=C H H • trans have bulky groups on opposite sides of C=C. CH3─ (CH2)5H C=C trans H (CH2)7─COOH

23. Hydrogenation & Trans Fatty Acids Most naturally occurring fatty acids have cis double bonds! • However, during hydrogenation, some cis double bonds are converted to trans double bonds. • In the body, trans fatty acids behave like saturated fatty acids. Why? • It is estimated that 2-4% of our total Calories is in the form of trans fatty acid. • Several studies reported that trans fatty acids raise LDL-cholesterol and lower HDL-cholesterol.

24. Hydrolysis • triacylglycerols split into glycerol and three fatty acids. • an acid or enzyme catalyst is required. + +

25. Saponification (Base Hydrolysis) + 3NaOH + 3 “soap”

26. 15.5 Glycerophospholipids • the most abundant lipids in cell membranes. • composed of glycerol, two fatty acids, phosphate, and an amino alcohol. Fatty acid Glycerol Fatty acid PO4 Amino alcohol

27. Polarity of Glycerophospholipids A glycerophospholipid has • 2 nonpolar fatty acid chains. • A phosphate group and a polar amino alcohol. CH3 │+ + HO−CH2−CH2−N−CH3 HO−CH2−CH2−NH3 │ choline CH3 ethanolamine + NH3 │ Amino alcohols HO−CH2−CH−COO− serine

28. Structure and Polarity of A Glycerophospholipid

29. Lecithin & Cephalin Lecithin and cephalin are glycerophospholipids • abundant in brain and nerve tissues. • found in egg yolk, wheat germ, and yeast.

30. 15.6 Steroids: Cholesterol, & Steroid Hormones

31. Steroid Nucleus Consists of: • 3 cyclohexane rings. • 1 cyclopentane ring. • no fatty acids. steroid nucleus

32. Cholesterol • is the most abundant steroid in the body. • has methyl CH3- groups, alkyl chain, and -OH attached to the steroid nucleus.

33. Cholesterol in the Body A normal, open artery. • is obtained from meats, milk, and eggs. • is synthesized in the liver. • is needed for cell membranes, brain and nerve tissue, steroid hormones, and Vitamin D. • clogs arteries when high levels form plaque. An artery clogged by cholesterol plaque

34. Cholesterol in Foods • is considered elevated if plasma cholesterol exceeds 200 mg/dL. • is synthesized in the liver and obtained from foods.

35. Lipoproteins: LDL, HDL, Etc… • combine lipids with proteins & phospholipids. • are soluble in water because the surface consists of polar lipids.

36. Types of Lipoproteins • differ in density, composition, and function. • include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs).

37. Transport of Lipoproteins in the Body