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

b. <IMAGE>

Draw the structure of the sphingomyelin that contains a myristic acid acyl group. Identify the hydrophilic head group and the hydrophobic tails in this molecule.

Draw the structure of the glycerophospholipid that contains a stearic acid acyl group, an oleic acid acyl group, and a phosphate bonded to ethanolamine.

Which of the following terms apply to the compound shown below? (Hint: Look at the functional groups and the bonds involved to begin analyzing the compound part by part in comparison to the lipids discussed in this chapter.) <IMAGE>

a. A phospholipid

Which of the following terms apply to the compound shown below? (Hint: Look at the functional groups and the bonds involved to begin analyzing the compound part by part in comparison to the lipids discussed in this chapter.) <IMAGE>

e. A lipid

As noted earlier (Section 22.3), he first step in glycolysis, which occurs within cells, is phosphorylation of glucose to glucose 6-phosphate. Why does this step prevent passive diffusion of glucose back out of the cell?

One of the constituents of the carnauba wax used in floor and furniture polish is an ester of a 32-carbon straight-chain alcohol with a C20:0 straight-chain carboxylic acid. Draw the structure of this ester. (Use subscripts to show the numbers of connected CH₂ groups.)

Complete hydrogenation of triacylglycerol C in Problem 23.20 yields a triacylglycerol of what fatty acid composition? Would the hydrogenation product of triacylglycerol C be more like the hydrogenation product of triacylglycerol A or B? Explain.

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?

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

Which of these fatty acids has the lower melting point? Explain why.

a. Linoleic acid

b. Stearic acid

Which of these fatty acids has the higher melting point? Explain why.

a. Linolenic acid

b. Stearic acid

Draw the structure of glyceryl trilaurate, which is made from glycerol and three lauric acid molecules.

There are two isomeric triacylglycerol molecules whose components are glycerol, one palmitic acid unit, and two stearic acid units. Draw the structures of both, and explain how they differ.

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 the structure of the product you would obtain on complete hydrogenation of the triacylglycerol in Problem 23.49. What is its name? Does it have a higher or lower melting temperature than the original triacylglycerol?

Tell how many different products you would obtain on hydrogenation of the triacylglycerol in Problem 23.49 if:

a. One double bond was converted to a single bond

b. Two double bonds were converted to single bonds

c. Three double bonds were converted to single bonds

d. All four double bonds were converted to single bonds

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.

<TABLE>

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.

<TABLE>

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

Why are glycerophospholipids more soluble in water than triacylglycerols?

Show the structure of a cerebroside made up of d-galactose, sphingosine, and myristic acid.

Can there be any chiral carbon atoms in triacylglycerols? If so, which ones can be chiral and what determines their chirality?

Draw the structure of a glycerophospholipid that contains palmitic acid, oleic acid, and the phosphate bonded to propanolamine.

Cardiolipin, a compound found in heart muscle, has the following structure. What products are formed if all ester bonds in the molecule are saponified by treatment with aqueous NaOH? <IMAGE>

Which process requires energy—passive or active transport? Why is energy sometimes required to move solute across the cell membrane?

Based on the information in Section 23.7, how would you expect each of these common metabolites to cross the cell membrane?

c. Ca²⁺

Based on the information in Section 23.7, how would you expect each of these common metabolites to cross the cell membrane?

a. NO (nitrous oxide)

Based on the information in Section 23.7, how would you expect each of these common metabolites to cross the cell membrane?

a. CO

Which of the following are saponifiable lipids? (Recall that ester bonds are broken by base hydrolysis.)

a. Progesterone

b. Glyceryl trioleate

c. A sphingomyelin

d. Prostaglandin E₁

e. A cerebroside

f. A lecithin