23. Lipids

Which one of the following statements accurately describes the difference between cephalins and lecithins?

Draw a glycerophospholipid with lauric acid at C1, myristic acid at C2, and choline bonded to phosphate.

Draw a cephalin with stearic acid at C1 and oleic acid at C2.

Draw a lecithin with palmitic acid at C1 and palmitoleic acid at C2.

Why are glycerophospholipids more soluble in water than triacylglycerols?

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

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

Identify the products formed by complete hydrolysis of all ester bonds in (a) the phosphatidylcholine on page 726.

A membrane lipid was isolated and completely hydrolyzed. The following products were detected: ethanolamine, phosphate, glycerol, palmitic acid, and oleic acid. Propose a structure for this membrane lipid, and name the family (Table 23.3) to which it belongs.

Identify the following glycerophospholipid, which is found in the nerves and spinal cord in the body, as a lecithin or cephalin, and list its components: 

<IMAGE>

Identify the following features of this phospholipid, which is needed for the brain and nerve tissues:

<IMAGE> 

a. Is the phospholipid formed from glycerol or sphingosine?

Palm oil has a high level of glyceryl tripalmitate (tripalmitin). Draw the condensed structural formula for glyceryl tripalmitate. (15.2, 15.3) 

<IMAGE>

Describe the similarities and differences between triacylglycerols and glycerophospholipids.

Draw the condensed structural formula for the cephalin that contains glycerol, two palmitic acids, phosphate, and ethanolamine (ionized).

Draw the condensed structural formula for a glycerophospholipid that contains glycerol, two stearic acids, phosphate, and ethanolamine (ionized). (15.2, 15.5)Draw the condensed structural formula for a glycerophospholipid that contains glycerol, two stearic acids, phosphate, and ethanolamine (ionized). (15.2, 15.5)

Mayonnaise is a thick mixture containing oil, vinegar (water-based), and eggs; the eggs contain a phospholipid molecule called lecithin. Mayonnaise cannot be made without lecithin. Explain why lecithin is a critical ingredient.

Compare the structure of a soap molecule to a phospholipid and explain why a soap’s polar head is smaller than that of a phospholipid.