Chem 5 PAL Worksheet Lipids Smith text Chapter 15 Principle: Fatty acids are carboxylic acids with long (usually > 14) carbon chains which can be saturated (no carbon-carbon double bonds) are unsaturated (one or more carboncarbon double bonds). The most important dietary fatty acids are palmitic, palmitoleic, oleic, linoleic, linolenic, stearic, docosahexaenoic (DHA) acids. 1. Draw the structures of the indicated fatty acids (FAs) using both condensed structural and skeletal formulas. For unsaturated, use only cis double bonds. Indicate which of the FAs are omega FAs and circle the double bond on the skeletal formula. A. C18:2 9,12 B. C24:0 C. C22:6 4,7,10,13,16,19 D. C16:1 9 2. Which FA will have the highest melting point? Explain. A. C14:0 B. C16:0 C. C16:1 D. C18:0 E. C18:1 1
Principle: FAs contain the carboxylic acid functional group and therefore undergo reactions similar to all CAs. 3. A. Draw a dissociation reaction for myristic acid, C14:0. B. Draw an equation for the reaction of myristic acid with NaOH. 4. Draw a reaction between myristic acid and 2-butanol. Principle: Waxes usually have the ester functional group and are formed by reaction of a long chain alcohol and a fatty acid. They are the simplest hydrolyzable lipids. 5. Complete the reactions. A. CH 3 (CH 2 ) 12 COOH +CH 3 (CH 2 ) 22 CH 2 OH B. O CH 3 (CH 2 ) 16 CH 2 OC(CH 2 ) 7 CH=CHCH 2 CH=CHCH 2 CH 2 CH 3 + H 2 O C. O CH 3 (CH 2 ) 14 COCH 2 (CH 2 ) 28 CH 3 + H 2 O (basic conditions) 2
Principle: Triacylglycerols (TAGs aka triglycerides) contain the ester functional group and are formed by reaction of 3 FAs with the triol glycerol. They are hydrolyzable lipids. 6. Differentiate between fats and oils both in terms of structure and physical properties. 7. Draw the TAG containing stearic, linolenic, and palmitoleic acids at the 1, 2, 3, positions, respectively. 8. Draw a complete hydrolysis reaction using the TAG in question #7 in A. acidic (e.g. HCl) and B. basic (e.g. KOH) conditions. A. B. 3
9. What are trans fats? Which would have a higher melting point, C16:1 9 with a cis double bond or C16:1 9 with a trans double bond? Explain. Why should you avoid trans fats? Principle: TAGs are a principle source of energy in the body and are metabolized by cellular combustion. 10. The CO 2 we exhale comes directly from oxidation of the foods we eat and nurses frequently monitor CO 2 exhalation in patients as an indicator of medical status (e.g. for excess CO 2 in acidosis or for decreased partial pressure of CO 2 due to lung dysfunction). Draw a complete, balanced combustion reaction for the lipid you drew in question # 7 (use molecular formulas). If the expired volume of air is 3 L, what partial pressure of CO 2 at STP would be generated by complete combustion of 10 g of this fat (if the patient is healthy, it would be about 35 mm Hg). Principle: Phospholipids (PLs) are a common type of membrane lipid formed from glycerol, two fatty acids, phosphate, and a polar head group. They are hydrolyzable lipids which contain ester and phosphoester bonds. 4
11. Draw a phospholipid containing palmitic and oleic FAs and ethanolamine (CH 2 OHCH 2 NH 2 ) as the head group. Ethanolamine attaches to the glycerol through the alcohol group. 12. Draw the complete hydrolysis reaction (acidic conditions) for the phospholipid in question # 11. Principle: Steroids are molecules with diverse biological functions and have a basic structure containing four fused rings. 13. Draw the structure and give the biological function of the steroids listed below (see pp. 524 and 525 in your text). 5
A. progesterone B. androsterone C. aldosterone D. cortisol 14. What are statins and what are they used for? What is their specific action in the body? Draw the structure of Lipitor (see p. 524). Then circle and name the functional groups it has. 6
Principle: There are four fat-soluble vitamins, each with an important biological role. 15. Draw each of the four fat soluble vitamins (see pp. 527, 528). Circle and name the functional groups and indicate the biological role of each one. 7