Chapter 19, Problem 19.29P

Label each compound as a hydrolyzable or nonhydrolyzable lipid.

1. prostaglandin
2. phosphoacylglycerol
3. triacylglycerol
4. lecithin
5. leukotriene
6. cholesterol
7. vitamin A

Interpretation Introduction

(a)

Interpretation:

Prostaglandin should be labeled as Hydrolyzable or non-hydrolyzable lipid.

Concept Introduction:

Lipids can be grouped as hydrolyzable and nonhydrolyzable. Hydrolyzable lipids can be broken down into smaller molecules by reacting with water. Hydrolyzable lipids usually contain an ester functional group which is hydrolyzable. There are three subgroups of hydrolyzable lipids as waxes, triacylglycerols and phospholipids. Nonhydrolyzable lipids cannot be broken down into smaller molecules by hydrolysis with water. There are subgroups of nonhydrolyzable lipids as steroids, fat-soluble vitamins and eicosanoids.

Answer to Problem 19.29P

Nonhydrolyzable

Explanation of Solution

Prostaglandin is a 20 carbon unsaturated carboxylic acid which contains a five-membered ring. A typical structure for prostaglandin is,

  

Prostaglandin does not contain an ester group. So, prostaglandin is nonhydrolyzable lipid.

Interpretation Introduction

(b)

Interpretation:

Triacylglycerol should be labeled as Hydrolyzable or non-hydrolyzable.

Concept Introduction:

Lipids can be grouped as hydrolyzable and nonhydrolyzable. Hydrolyzable lipids can be broken down into smaller molecules by reacting with water. Hydrolyzable lipids usually contain an ester functional group which is hydrolyzable. There are three subgroups of hydrolyzable lipids as waxes, triacylglycerols and phospholipids. Nonhydrolyzable lipids cannot be broken down into smaller molecules by hydrolysis with water. There are subgroups of nonhydrolyzable lipids as steroids, fat-soluble vitamins and eicosanoids.

Answer to Problem 19.29P

Hydrolyzable

Explanation of Solution

Triacylglycerol is produced by reacting a glycerol molecule with three molecules of fatty acids by an ester linkage.

  

Triacylglycerol has three ester linkages. So, triacylglycerol is a hydrolyzable lipid.

Interpretation Introduction

(c)

Interpretation:

Leukotriene should be labeled as Hydrolyzable or non-hydrolyzable.

Concept Introduction:

Lipids can be grouped as hydrolyzable and nonhydrolyzable. Hydrolyzable lipids can be broken down into smaller molecules by reacting with water. Hydrolyzable lipids usually contain an ester functional group which is hydrolyzable. There are three subgroups of hydrolyzable lipids as waxes, triacylglycerols and phospholipids. Nonhydrolyzable lipids cannot be broken down into smaller molecules by hydrolysis with water. There are subgroups of nonhydrolyzable lipids as steroids, fat-soluble vitamins and eicosanoids.

Answer to Problem 19.29P

Nonhydrolyzable

Explanation of Solution

Leukotrienes belong to the family of eicosanoids. Leukotrienes are synthesized by arachidonic acid. A typical structure for leukotriene is,

  

Leukotrienes have no ester linkages. So, leukotrienes are nonhydrolyzable lipids.

Interpretation Introduction

(d)

Interpretation:

Vitamin A should be labeled as hydrolyzable or non-hydrolyzable.

Concept Introduction:

Lipids can be grouped as hydrolyzable and nonhydrolyzable. Hydrolyzable lipids can be broken down into smaller molecules by reacting with water. Hydrolyzable lipids usually contain an ester functional group which is hydrolyzable. There are three subgroups of hydrolyzable lipids as waxes, triacylglycerols and phospholipids. Nonhydrolyzable lipids cannot be broken down into smaller molecules by hydrolysis with water. There are subgroups of nonhydrolyzable lipids as steroids, fat-soluble vitamins and eicosanoids.

Answer to Problem 19.29P

Nonhydrolyzable

Explanation of Solution

Vitamin A is a group of several unsaturated fatty acids. It includes retinol which has an alcohol functional group, retinal which is an aldehyde and retinoic acid which is a carboxylic acid.

  

No structure has an ester linkage. So vitamin A is nonhydrolyzable lipid.

Interpretation Introduction

(e)

Interpretation:

Phoshoacylglycerol should be labeled as hydrolyzable or non-hydrolyzable.

Concept Introduction:

Lipids can be grouped as hydrolyzable and nonhydrolyzable. Hydrolyzable lipids can be broken down into smaller molecules by reacting with water. Hydrolyzable lipids usually contain an ester functional group which is hydrolyzable. There are three subgroups of hydrolyzable lipids as waxes, triacylglycerols and phospholipids. Nonhydrolyzable lipids cannot be broken down into smaller molecules by hydrolysis with water. There are subgroups of nonhydrolyzable lipids as steroids, fat-soluble vitamins and eicosanoids.

Answer to Problem 19.29P

Hydrolyzable

Explanation of Solution

Phosphoacylglycerols are esterified glycerol in which, two hydroxyl groups of glycerol are esterified with fatty acids and one hydroxyl is esterified with phosphoric acid.

  

Since phosphoacylglycerol has ester linkages, it is a hydrolyzable lipid.

Interpretation Introduction

(f)

Interpretation:

Lecithin should be labeled as hydrolyzable or non-hydrolyzable.

Concept Introduction:

Lipids can be grouped as hydrolyzable and nonhydrolyzable. Hydrolyzable lipids can be broken down into smaller molecules by reacting with water. Hydrolyzable lipids usually contain an ester functional group which is hydrolyzable. There are three subgroups of hydrolyzable lipids as waxes, triacylglycerols and phospholipids. Nonhydrolyzable lipids cannot be broken down into smaller molecules by hydrolysis with water. There are subgroups of nonhydrolyzable lipids as steroids, fat-soluble vitamins and eicosanoids.

Answer to Problem 19.29P

Hydrolyzable

Explanation of Solution

Lecithins are mixtures of glycerophospholipids. As glycerophospholipids are esterified form of glycerol with two fatty acids and phosphoric acid. Lecithin contains ester linkages. So, lecithin is a hydrolyzable lipid. The structure of phosphatidylcholine which is a type of phospholipid in lecithin is given below.

  

Interpretation Introduction

(g)

Interpretation:

Cholesterol should be labeled as hydrolyzable or non-hydrolyzable.

Concept Introduction:

Lipids can be grouped as hydrolyzable and nonhydrolyzable. Hydrolyzable lipids can be broken down into smaller molecules by reacting with water. Hydrolyzable lipids usually contain an ester functional group which is hydrolyzable. There are three subgroups of hydrolyzable lipids as waxes, triacylglycerols and phospholipids. Nonhydrolyzable lipids cannot be broken down into smaller molecules by hydrolysis with water. There are sub groups of nonhydrolyzable lipids as steroids, fat-soluble vitamins and eicosanoids.

Answer to Problem 19.29P

Nonhydrolyzable

Explanation of Solution

Cholesterol is a type of sterol and has no ester linkages. So, cholesterol is nonhydrolyzable lipid.