23. Lipids

Which of the following fatty acids would you expect to be more soluble in cyclohexane?

Provide a condensed structural formula for a fatty acid with 18 carbons (18:0) and give its common name.

Provide a skeletal structure for Linolenic acid.

Use Figure 23.1 to identify the family of lipids to which each of these molecules belongs.

b.

Draw the complete structural formula of arachidonic acid (Table 23.1) in a way that shows the cis stereochemistry of its four double bonds.

Draw an 18-carbon saturated fatty acid. Is this a “straight-chain” molecule or a “bent” molecule?

Draw an 18-carbon unsaturated fatty acid that contains two carbon–carbon double bonds, one on carbon 6 and one on carbon 9 (count starting with the carboxyl carbon). Is this a “straight-chain” molecule or a “bent” molecule?

Dietary guidelines suggest we limit our intake of butter due to the cholesterol content and substitute oils or margarine. The following table shows the major fatty acid distribution for a typical stick of margarine and also for butter. Values are percentages.

a. Which contains more monounsaturated fatty acids?

Dietary guidelines suggest we limit our intake of butter due to the cholesterol content and substitute oils or margarine. The following table shows the major fatty acid distribution for a typical stick of margarine and also for butter. Values are percentages.

c. Which is likely to contain fewer trans-fatty acids

Are the carbon–carbon double bonds in naturally occurring fatty acids primarily cis or trans?

What is the difference in the location of the first double bond in an omega-3 and an omega-6 fatty acid (see Chemistry Link to Health “Omega-3 Fatty Acids in Fish Oils”)?

 Identify each of the following as a saturated, monounsaturated, polyunsaturated, omega-3, or omega-6 fatty acid:

a.

Describe some similarities and differences in the structures of a saturated fatty acid and an unsaturated fatty acid.

Draw the line-angle formula for each of the following fatty acids:

a. palmitic acid

For each of the following fatty acids, give the shorthand notation for the number of carbon atoms and double bonds, and classify as saturated, monounsaturated, or polyunsaturated:

a. lauric acid