Section 19.

1
Structure and Classification of Lipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 1

Chapter 19
Chapter Outline

Return to TOC

2
Chapter 19
Chapter Outline

Return to TOC

3
 Chapter 19
Chapter Outline

19.1 Structure and classification of lipids

19.2 Types of fatty acids
19.3 Physical properties of fatty acids
19.4 Energy-storage lipids: Triacylglycerols
19.5 Dietary considerations and triacylglycerols
19.6 Chemical reactions of triacylglycerols
19.7 Membrane lipids: Phospholipids
19.8 Membrane lipids: Sphingoglycolipids
19.9 Membrane lipids: Cholesterol
19.10 Cell membranes
19.11 Emulsification lipids: Bile acids
19.12 Messenger lipids: Steroid hormones
19.13 Messenger lipids: Eicosanoids
19.14 Protective-coating lipids: Biological waxes
19.15 Saponifiable and nonsaponifiable lipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 2

 Section 19.1
Structure and Classification of Lipids

Lipids
• Lipid: An organic compound found in living
organisms that is insoluble (or only sparingly
soluble) in water but soluble in non-polar organic
solvents
• Unlike other biomolecules, lipids do not have a
common structural feature that serves as the
basis for defining such compounds
• Classification is based on two methods
– Biochemical function
– Saponification
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 5

 Section 19.1
Structure and Classification of Lipids

Classification based on Biochemical Function

• For purposes of simplicity of study, lipids are

divided into five categories based on their
biochemical function:
– Energy-storage lipids (triacylglycerols)
– Membrane lipids (phospholipids, sphingoglycolipids,
and cholesterol)
– Emulsification lipids (bile acids)
– Messenger lipids (steroid hormones and
eicosanoids)
– Protective-coating lipids (biological waxes)

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 6

Section 19.1
Structure and Classification of Lipids

Return to TOC

7
 Section 19.1
Structure and Classification of Lipids

Classification Based on Saponification

• Saponification reaction - Hydrolysis reaction that

occurs in a basic solution
• Based on saponification reactions, lipids are
divided into two categories:
– Saponifiable lipids (triacylglycerols, phospholipids,
sphingoglycolipids, cholesterol, and biological waxes)
– Nonsaponifiable lipids (bile acids, steroid
hormones, and eicosanoids)

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 8

Section 19.1
Structure and Classification of Lipids

Return to TOC

9
 Section 19.1
Structure and Classification of Lipids

Structural Diversity of Lipids

• Lipids exhibit structural diversity

• Some are esters, some are amides, and some
are alcohols (acyclic, cyclic, and polycyclic)

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 10

 Section 19.1
Structure and Classification of Lipids

Figure 19.1 - Structural Formula of Types of Lipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 11

 Section 19.1
Structure and Classification of Lipids

A lipid is an organic compound found in living

organisms that is:

a.soluble in water and insoluble in nonpolar organic solvents.

b.soluble in water and soluble in nonpolar organic solvents.
c.insoluble in water and insoluble in nonpolar organic
solvents.
d.insoluble in water and soluble in nonpolar organic solvents.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 12

 Section 19.1
Structure and Classification of Lipids

A lipid is an organic compound found in living

organisms that is:

a.soluble in water and insoluble in nonpolar organic solvents.

b.soluble in water and soluble in nonpolar organic solvents.
c.insoluble in water and insoluble in nonpolar organic
solvents.
d.insoluble in water and soluble in nonpolar organic solvents.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 13

 Section 19.2
Types of Fatty Acids

Fatty Acids - An Introduction

• Fatty acids: Naturally occurring monocarboxylic

acids with linear (unbranched) carbon chain
– Have even number of carbon atoms
• Long-chain fatty acids (C12 to C26)
• Medium-chain fatty acids (C8 to C10)
• Short-chain fatty acids (C4 to C6)
• Two types:
– Saturated - All C–C bonds are single bonds
– Unsaturated
• Monounsaturated
• Polyunsaturated
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 14

 Section 19.2
Types of Fatty Acids

Saturated Fatty Acids

• Fatty acids with a carbon chain in which all C–C

bonds are single bonds
• Numbering starts from the end of –COOH
group
• Consider the structural notations for palmitic
acid:

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 15

 Section 19.2
Types of Fatty Acids

Unsaturated Fatty Acids

• Monounsaturated fatty acid: Fatty acid with a

carbon chain in which one carbon–carbon
double bond is present
• There are different ways of depicting the
structure

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 16

 Section 19.2
Types of Fatty Acids

Unsaturated Fatty Acids

• Monounsaturated fatty acid: Fatty acid with a

carbon chain in which one carbon–carbon
double bond is present
• There are different ways of depicting the
structure

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 17

Section 19.2
Types of Fatty Acids

Exercise
Illustrate the following items to line structural formula

1. Palmitoleic acid (C16H30COOH) (hexadec-9-oeic acid)

2. Lauric acid (C11H23COOH)

Return to TOC

18
 Section 19.2
Types of Fatty Acids

Polyunsaturated Fatty Acids (PUFAs)

• Fatty acids with a carbon chain in which two or

more carbon–carbon double bonds are present
• Up to six double bonds are found in
biochemically important PUFAs

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 19

 Section 19.2
Types of Fatty Acids

Double-Bond Position in Unsaturated Fatty Acids

• Numbering starts from the other end of –COOH

• Structural notation indicates number of C atoms
• Example:
– 18:2 signifies that a fatty acid has 18 carbons with 2
double bonds

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 20

 Section 19.2
Types of Fatty Acids

Types of Unsaturated Fatty Acids

• Omega (ω)-3 fatty acid: Unsaturated fatty acid

with its endmost double bond three carbon
atoms away from its methyl end
• Omega (ω)-6 fatty acid: Unsaturated fatty acid
with its endmost double bond six carbon atoms
away from its methyl end

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 21

 Section 19.2
Types of Fatty Acids

A fatty acid is a naturally occurring _____ acid that

nearly always contains an _____ number of carbon
atoms with a carbon chain that is _____.

a.monocarboxylic; even; branched

b.dicarboxylic; odd; unbranched
c.monocarboxylic; even; unbranched
d.dicarboxylic; even; branched

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 22

 Section 19.2
Types of Fatty Acids

A fatty acid is a naturally occurring _____ acid that

nearly always contains an _____ number of carbon
atoms with a carbon chain that is _____.

a.monocarboxylic; even; branched

b.dicarboxylic; odd; unbranched
c.monocarboxylic; even; unbranched
d.dicarboxylic; even; branched

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 23

 Section 19.2
Types of Fatty Acids

Which of the following statements is true about the

classification of fatty acids?

a.They are classified as saturated, monounsaturated, or

polyunsaturated fatty acids.
b.They are classified as saturated or branched unsaturated
fatty acids.
c.They are classified as saturated or polyunsaturated fatty
acids.
d.None of the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 24

 Section 19.2
Types of Fatty Acids

Which of the following statements is true about the

classification of fatty acids?

a.They are classified as saturated, monounsaturated, or

polyunsaturated fatty acids.
b.They are classified as saturated or branched unsaturated
fatty acids.
c.They are classified as saturated or polyunsaturated fatty
acids.
d.None of the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 25

 Section 19.3
Physical Properties of Fatty Acids

Water Solubility

• Short-chain fatty acids have some solubility,

whereas long-chain fatty acids are insoluble
• Short-chain fatty acids are sparingly soluble
because of the presence of carboxylic group

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 26

 Section 19.3
Physical Properties of Fatty Acids

Melting Point

• Depends upon the

following:
– Length of carbon
chain
– Degree of
unsaturation (number
of double bonds in a
molecule)

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 27

 Section 19.3
Physical Properties of Fatty Acids

• Number of “bends” in
a fatty acid chain
increases as the
number of double
bonds increases
• Less packing occurs
• Melting point is lower
• Tend to be liquid at
room temperature

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 28

 Section 19.3
Physical Properties of Fatty Acids

Which of the following best describe the physical

properties of fatty acids?

a.Melting points of fatty acids are influenced by the carbon

chain length.
b.Melting points of fatty acids are influenced by their degree
of unsaturation.
c.All physical properties of fatty acids are influenced by the
length and degree of unsaturation of their carbon chain.
d.All the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 29

 Section 19.3
Physical Properties of Fatty Acids

Which of the following best describe the physical

properties of fatty acids?

a.Melting points of fatty acids are influenced by the carbon

chain length.
b.Melting points of fatty acids are influenced by their degree
of unsaturation.
c.All physical properties of fatty acids are influenced by the
length and degree of unsaturation of their carbon chain.
d.All the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 30

Section 19.3
Physical Properties of Fatty Acids

Return to TOC

31
 Section 19.4
Energy-Storage Lipids: Triacylglycerols

Energy-Storage Materials

• With the notable exception of nerve cells, human

cells store small amounts of energy-providing
materials
– Carbohydrate glycogen - Most widespread energy
storage material present in small amounts
• Major energy-storage material is triacylglycerol
– Concentrated primarily in special cells (adipocytes)
which are nearly filled with triacylglycerols

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 32

 Section 19.4
Energy-Storage Lipids: Triacylglycerols

Two Types of Triacylglycerols

• Simple triacylglycerol: Triester formed from the

esterification if glycerol with three identical fatty
acid molecules
– Naturally occurring simple triacylglycerols are rare
• Mixed triacylglycerol: Triester formed from the
esterification of glycerol with more than one kind
of fatty acid molecule

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 33

 Section 19.4
Energy-Storage Lipids: Triacylglycerols

Fats and Oils

• Fats:
– Predominantly Saturated
– Solids or semisolids at room temperature
– Source: Animals
• Oils:
– Predominantly unsaturated
– Liquids at room temperature
– Sources: Plants and fish oil
• Pure oils and fats are colorless, odorless, and
tasteless
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 34

 Section 19.4
Energy-Storage Lipids: Triacylglycerols

Triacylglycerols are _____ in their ability to store

energy when compared to glycogen, the energy
storing form of glucose in the human body.

a.less efficient
b.more efficient
c.equally efficient
d.insignificant

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 35

 Section 19.4
Energy-Storage Lipids: Triacylglycerols

Triacylglycerols are _____ in their ability to store

energy when compared to glycogen, the energy
storing form of glucose in the human body.

a.less efficient
b.more efficient
c.equally efficient
d.insignificant

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 36

 Section 19.5
Dietary Considerations and Triacylglycerols
Studies Concerning Role of Dietary Factors as a Cause
of Disease
• Nations whose citizens have high dietary intakes
of fats and oils tend to have higher incidences of
heart disease and certain types of cancers
• Typical American diet contains too much fat
– Americans are being asked to reduce their total
dietary fat intake
• Other studies show that risk factors involve more
than simply the total amount of triacylglycerols
consumed
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 37

 Section 19.5
Dietary Considerations and Triacylglycerols

“Good Fats” Versus “Bad Fats”

• Studies indicate that type of dietary fat and

amount of dietary fat are important to determine
body responses to dietary fat
• Current recommended amount for total fat
intake in calories:
– 15% - Monounsaturated fat
– 10% - Polyunsaturated
– <10% - Saturated fats

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 38

 Section 19.5
Dietary Considerations and Triacylglycerols

“Good Fats” Versus “Bad Fats”

• Studies also indicate that:

– Saturated fats are considered “bad fats”
– Monounsaturated fats are considered “good fats”
– Polyunsaturated fats can be both “good fats” and
“bad fats”
• Omega fats are important

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 39

 Section 19.5
Dietary Considerations and Triacylglycerols

Omega-6 and Omega-3 Fatty Acids in American Diet

• American diet is high in omega-6 fatty acids and

deficient in omega-3 fatty acids
– Fish are a good source for omega-3 fatty acids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 40

 Section 19.5
Dietary Considerations and Triacylglycerols

Essential Fatty Acids

• Fatty acids that must be obtained from dietary

sources because they cannot be synthesized
within the body
• Two most important essential fatty acids are:
– Linoleic acid (18:2) - Omega 6
– Linolenic acid (18:3) - Omega 3
• Needed for proper membrane structure
• Serve as starting materials for the production of
several nutritionally important longer-chain omega-6
and omega-3 fatty acids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 41

 Section 19.5
Dietary Considerations and Triacylglycerols

Deficiency of Linoleic and Linoleic Acid

• Results in:
– Skin redness
– Infections and dehydration
– Liver abnormalities

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 42

 Section 19.5
Dietary Considerations and Triacylglycerols

Fat and Fatty Acid Composition of Nuts

• Numerous studies now indicate that eating nuts

can have a strong protective effect against
coronary heart disease
– Low amounts of saturated fatty acids
– Also contain valuable antioxidant vitamins, minerals,
and plant fiber protein

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 43

 Section 19.5
Dietary Considerations and Triacylglycerols

Considerable research in the past two decades

has shown that high intake of dietary
triacylglycerols causes diseases such as obesity,
cancer, hypertension, and atherosclerosis. This is
not true for the Inuit people of Greenland because
their diet is high in _____ fatty acids.

a.saturated
b.Omega-3
c.Omega-6
d.Omega-9
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 44

 Section 19.5
Dietary Considerations and Triacylglycerols

Considerable research in the past two decades

has shown that high intake of dietary
triacylglycerols causes diseases such as obesity,
cancer, hypertension, and atherosclerosis. This is
not true for the Inuit people of Greenland because
their diet is high in _____ fatty acids.

a.saturated
b.Omega-3
c.Omega-6
d.Omega-9
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 45

Section 19.5
Dietary Considerations and Triacylglycerols

Group Activity
1. Each group will be assigned a particular country
(through lottery) to analyse its dietary considerations.

2. Make a one-pager presentation about their diets.

Countries to choose from:

● Philippines
● Canada
● Italy
● Turkey
● Pakistan
● South Korea
● Mexico
● New Zealand

Return to TOC

46
 Section 19.6
Chemical Reactions of Triacylglycerols
Hydrolysis

• Chemical properties of triacylglycerols are typical

of the functional groups esters and alkenes
• Carried out by enzymes produced by the
pancreas in a stepwise manner
– Breaking of outer fatty acids produces diacylglycerol
and monoacylglycerol
• Complete hydrolysis - When all three fatty acids
are removed
• Partial hydrolysis - When one or more fatty acid
residue remains
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 47

Section 19.6
Chemical Reactions of Triacylglycerols

Return to TOC

48
 Section 19.6
Chemical Reactions of Triacylglycerols
Carboxylic Acid = RCOOH
Saponification Carboxylic Salts = RCOONa+

• Hydrolysis in basic solution

• Products: Fatty acid and glycerol salts Hydrolysis of Ester
linkages

saponification

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 49

Section 19.6
Chemical Reactions of Triacylglycerols

Return to TOC

50
Section 19.6
Chemical Reactions of Triacylglycerols

Laboratory Activity 3: #Sa(b)ponification

• All eight teams will be performing saponification on
October 29.
• Theme for soap making presentation:
– Group 1 and 5 → Era
– Group 2 and 6 → Istitik
– Group 3 and 7 → Camp
– Group 4 and 8 → Play

• Requirements:
– Documentation
– 2 soap replicates for submission with packaging
– Presentation

Return to TOC

51
 Section 19.6
Chemical Reactions of Triacylglycerols

Hydrogenation

• Addition of hydrogen across C–C multiple

bonds, which increases degree of saturation
• Many food products are produced by partial
hydrogenation of oils and fats
– Peanut oil 🡪 Peanut butter
– Liquid plant oil 🡪 Margarine

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 52

Section 19.6
Chemical Reactions of Triacylglycerols

Return to TOC

53
 Section 19.6
Chemical Reactions of Triacylglycerols

Oxidation

• Double bonds in triacylglycerols are subject to

oxidation with oxygen (an oxidizing agent)
• Leads to C=C breakage that produces both
aldehyde and carboxylic acid products
– Products often have objectionable odors, and fats
and oils are said to be rancid
• To avoid this unwanted oxidation process,
antioxidants are added as preservatives
– Example: Vitamin C and vitamin E are naturally
occurring antioxidant
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 54

Section 19.6
Chemical Reactions of Triacylglycerols

Return to TOC

55
 Section 19.6
Chemical Reactions of Triacylglycerols

What are the important triacylglycerol reactions?

a.Hydrolysis, hydrogenation, and oxidation

b.Hydrogenation, saponification, and hydrolysis
c.Hydrolysis, saponification, hydrogenation, and oxidation
d.Hydrolysis, saponification, oxidation, and
hydrohalogenation

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 56

 Section 19.6
Chemical Reactions of Triacylglycerols

What are the important triacylglycerol reactions?

a.Hydrolysis, hydrogenation, and oxidation

b.Hydrogenation, saponification, and hydrolysis
c.Hydrolysis, saponification, hydrogenation, and oxidation
d.Hydrolysis, saponification, oxidation, and
hydrohalogenation

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 57

 Section 19.6
Chemical Reactions of Triacylglycerols

Partial triacylglycerol hydrolysis occurs during the

process of digestion in the human body, and it
produces a _____ and _____.

a.glycerol; three fatty acids

b.diacylglycerol; two fatty acids
c.monoacylglycerol; one fatty acid
d.monoacylglycerol; two fatty acids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 58

 Section 19.6
Chemical Reactions of Triacylglycerols

Partial triacylglycerol hydrolysis occurs during the

process of digestion in the human body, and it
produces a _____ and _____.

a.glycerol; three fatty acids

b.diacylglycerol; two fatty acids
c.monoacylglycerol; one fatty acid
d.monoacylglycerol; two fatty acids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 59

 Section 19.6
Chemical Reactions of Triacylglycerols

Which of the following statements regarding

saponification of triacylglycerols is correct?

a.Saponification is a hydrolysis reaction carried out in an

alkaline (basic) solution.
b.Saponification of animal fats is the process by which soaps
were made in pioneer times.
c.Saponification is a hydrolysis reaction resulting in the
formation of carboxylate ions.
d.All the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 60

 Section 19.6
Chemical Reactions of Triacylglycerols

Which of the following statements regarding

saponification of triacylglycerols is correct?

a.Saponification is a hydrolysis reaction carried out in an

alkaline (basic) solution.
b.Saponification of animal fats is the process by which soaps
were made in pioneer times.
c.Saponification is a hydrolysis reaction resulting in the
formation of carboxylate ions.
d.All the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 61

 Section 19.6
Chemical Reactions of Triacylglycerols

What process is utilized to convert liquid plant oils

into semi-solid materials that, when ingested, play
a role in raising blood cholesterol levels?

a.Halogenation
b.Hydrohalogenation
c.Hydrogenation
d.Hydrolysis

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 62

 Section 19.6
Chemical Reactions of Triacylglycerols

What process is utilized to convert liquid plant oils

into semi-solid materials that, when ingested, play
a role in raising blood cholesterol levels?

a.Halogenation
b.Hydrohalogenation
c.Hydrogenation
d.Hydrolysis

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 63

 Section 19.6
Chemical Reactions of Triacylglycerols

What process results in breaking the

carbon–carbon double bonds producing both short
chain aldehyde and carboxylic acid products
causing the fats and oils to become rancid?

a.Oxidation
b.Hydrolysis
c.Saponification
d.Hydrogenation

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 64

 Section 19.6
Chemical Reactions of Triacylglycerols

What process results in breaking the

carbon–carbon double bonds producing both short
chain aldehyde and carboxylic acid products
causing the fats and oils to become rancid?

a.Oxidation
b.Hydrolysis
c.Saponification
d.Hydrogenation

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 65

Section 19.6
Chemical Reactions of Triacylglycerols

Return to TOC

66
 Section 19.7
Membrane Lipids: Phospholipids

An Introduction

• All cells are surrounded by a membrane that

confines their contents
• Up to 80% of the mass of a cell membrane can
be lipid materials dominated by phospholipids
• Phospholipid: Lipid that contains one or more
fatty acids, a phosphate group, a platform
molecule to which the fatty acid(s) and the
phosphate group are attached, and an alcohol
that is attached to the phosphate group

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 67

 Section 19.7
Membrane Lipids: Phospholipids

Types of Phospholipids Based on Platform Molecule

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 68

Section 19.7
Membrane Lipids: Phospholipids

Return to TOC

69
 Section 19.7
Membrane Lipids: Phospholipids

Glycerophospholipids

• Undergo hydrolysis and saponification reactions

in a manner similar to that for triacylglycerols
• The alcohol attached to the phosphate group in
a glycophospholipid is usually one of three
amino alcohols:
– Choline - Phosphatidylcholines
– Ethanolamine - Phosphatidylethanolamines
– Serine - Phosphatidylserines

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 70

 Section 19.7
Membrane Lipids: Phospholipids

Glycerophospholipids

• Lipids that contain two fatty acids and a

phosphate group esterified to a glycerol
molecule and an alcohol esterified to the
phosphate group
• All attachments (bonds) between groups are
ester linkages
– Contain four ester linkages when contrasted to three
ester linkages in triacylglycerols

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 71

 Section 19.7
Membrane Lipids: Phospholipids

Glycerophospholipids

• Structurally glycerophospholipids are similar to

triacylglycerols, but they have different
biochemical functions
– Triacylglycerols serve as energy-storage molecules
– Glycerophospholipids function as components of cell
membranes
– A major structural difference between the two types of
lipids is that of their “polarity”, which is responsible for
their differing biochemical functions
• Triacylglycerols are a nonpolar
• Glycerophospholipids are polar
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 72

 Section 19.7
Membrane Lipids: Phospholipids

Sphingophospholipids

• Structures based on the 18-carbon

monounsaturated aminodialcohol sphingosine
• Contains one fatty acid and one phosphate
group attached to a sphingosine molecule, and
an alcohol attached to the phosphate group

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 73

 Section 19.7
Membrane Lipids: Phospholipids

Sphingophospholipids

• Participate in hydrolysis and saponification

reaction
• Sphingophospholipids in which the alcohol
esterified to the phosphate group is choline are
called sphingomyelins
– Found in all cell membranes and are important
structural components of the myelin sheath of
neurons

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 74

Section 19.7
Membrane Lipids: Phospholipids

Return to TOC

75
Section 19.7
Membrane Lipids: Phospholipids

Return to TOC

76
 Section 19.7
Membrane Lipids: Phospholipids

What is the most abundant type of membrane

lipid?

a.Cholesterol
b.Sphingoglycolipids
c.Phospholipids
d.Eicosanoids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 77

 Section 19.7
Membrane Lipids: Phospholipids

What is the most abundant type of membrane

lipid?

a.Cholesterol
b.Sphingoglycolipids
c.Phospholipids
d.Eicosanoids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 78

 Section 19.8
Membrane Lipids: Sphingoglycolipids

Sphingoglycolipids

• Contains both a fatty acid

and a carbohydrate
component attached to a
sphingosine molecule

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 79

 Section 19.8
Membrane Lipids: Sphingoglycolipids

Cerebrosides

• Simplest sphingoglycolipids
• Contain a single monosaccharide unit–either
glucose or galactose
• Occur primarily in brain (7% of dry mass)

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 80

 Section 19.8
Membrane Lipids: Sphingoglycolipids

Gangliosides

• Complex sphingoglycolipids
• Contain a branched chain of up to seven
monosaccharide residues
• Occur in the gray matter of the brain as well as
in the myelin sheath

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 81

 Section 19.8
Membrane Lipids: Sphingoglycolipids

What is the membrane lipid, sphingoglycolipid,

made up of?

• sphingosine; fatty acid; monosaccharide

• sphingosine; fatty acid; oligosaccharide
• sphingosine; glycerol; fatty acid
• Both (a) and (b)

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 82

 Section 19.8
Membrane Lipids: Sphingoglycolipids

What is the membrane lipid, sphingoglycolipid,

made up of?

• sphingosine; fatty acid; monosaccharide

• sphingosine; fatty acid; oligosaccharide
• sphingosine; glycerol; fatty acid
• Both (a) and (b)

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 83

Section 19.8
Membrane Lipids: Sphingoglycolipids

Return to TOC

84
Section 19.8
Membrane Lipids: Sphingoglycolipids

Return to TOC

85
 Section 19.9
Membrane Lipids: Cholesterol

Cholesterol - Third Major Type of Membrane Lipid

• Is a steroid
– Lipid whose structure is based on a fused-ring
system of three 6-membered rings and one
5-membered ring
• Cholesterol: C27 steroid molecule and
precursor for other steroid-based lipids
– Important in human cell membranes, nerve tissue,
and brain tissue
– Important in chemical synthesis of various hormones
and vitamins essential for life

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 86

Section 19.9
Membrane Lipids: Cholesterol
methyl group
three 6-membered
rings

one
5-membered
ring

Alcohol group
Return to TOC

87
 Section 19.9
Membrane Lipids: Cholesterol

Cholesterol in Food

• Liver synthesizes almost 1g of cholesterol

everyday
– Not necessary to consume in the form of diet
• Cholesterol ingestion decreases biosynthetic
cholesterol production
• Animal food contains lots of cholesterol
• Plant food contains negligible amounts of
cholesterol

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 88

Section 19.9
Membrane Lipids: Cholesterol

Return to TOC

89
 Section 19.9
Membrane Lipids: Cholesterol

The membrane lipid cholesterol is a steroid whose

structure is based on a fused-ring system that
involves _____ six-membered ring(s) and _____
five-membered ring(s).

a.2, 2
b.3, 2
c.3, 1
d.1, 3

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 90

 Section 19.9
Membrane Lipids: Cholesterol

The membrane lipid cholesterol is a steroid whose

structure is based on a fused-ring system that
involves _____ six-membered ring(s) and _____
five-membered ring(s).

a.2, 2
b.3, 2
c.3, 1
d.1, 3

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 91

 Section 19.10
Cell Membranes

Cell Membrane (Plasma Membrane)

• Lipid-based structure that separates aqueous

interior of a cell from the aqueous environment
surrounding the cell
– Up to 80% of plasma membrane is lipid material
• The membranes are lipid bilayers made up of
phospholipids
– Lipid bilayer: Nonpolar tails of phospholipids are in
the middle and polar heads are on the surface
• 6–9 nanometers thick
• Contains at least one unsaturated fatty acid

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 92

 Section 19.10
Cell Membranes

Cholesterol and Cell Membrane

• Cholesterol molecules are also components of

plasma membranes
– Cholesterol helps regulate membrane fluidity–the
fused-ring system does not allow rotation of fatty acid
tails in the vicinity
– Fits between fatty acid chains of the lipid bilayer

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 93

 Section 19.10
Cell Membranes

Membrane Proteins

• Lipid bilayers also contain proteins

– Responsible for moving substances such as nutrients
and electrolytes across the membrane
– Act as receptors that bind hormones and
neurotransmitters
• The membrane proteins and some lipids further
react with carbohydrate molecules
– Act as markers, substances that play roles in
processes by which different cells recognize each
other

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 94

 Section 19.10
Cell Membranes
Figure 19.21 - Proteins as Important Structural
Components of Cell Membranes

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 95

 Section 19.10
Cell Membranes

Transport Across Cell Membranes

• To maintain cellular processes, various types of

molecules are transported across the cell
membranes
• Three types of transport:
– Passive transport
– Facilitated transport
– Active transport

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 96

 Section 19.10
Cell Membranes

Passive Transport

• Process in which a substance moves across a

cell membrane by diffusion from a region of
higher concentration to a region of lower
concentration
– No cellular energy expenditure
– Only a few types of molecules, including O2, N2, urea,
and ethanol, can cross membranes by this process

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 97

 Section 19.10
Cell Membranes

Facilitated Transport

• Process in which a substance moves across a

cell membrane, with the aid of a membrane
protein, from a region of higher concentration to
a region of lower concentration
– No cellular energy expenditure
– Specific protein carriers or transporters are involved
in the process

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 98

 Section 19.10
Cell Membranes

Active Transport

• Process in which a substance moves across a

cell membrane, with the aid of membrane
proteins, against a concentration gradient
– Involves expenditure of cellular energy
• Supplied by ATP molecules
– Proteins involved in active transport are called
“pumps”

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 99

Section 19.10
Cell Membranes

Return to TOC

100
 Section 19.10
Cell Membranes

Which of the following polarity-based descriptions

is correct for the interior of a lipid bilayer?

a.Polar heads
b.Nonpolar heads
c.Nonpolar tails
d.None of the above

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 101

 Section 19.10
Cell Membranes

Which of the following polarity-based descriptions

is correct for the interior of a lipid bilayer?

a.Polar heads
b.Nonpolar heads
c.Nonpolar tails
d.None of the above

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 102

 Section 19.10
Cell Membranes

What type of transport across membranes requires

the expenditure of cellular energy?

a.Passive
b.Facilitated
c.Active
d.Dialysis

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 103

 Section 19.10
Cell Membranes

What type of transport across membranes requires

the expenditure of cellular energy?

a.Passive
b.Facilitated
c.Active
d.Dialysis

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 104

 Section 19.11
Emulsification Lipids: Bile Acids

• Emulsifier: Substance that can disperse and

stabilize water-insoluble substances as colloidal
particles in an aqueous solution

• Bile acid: Cholesterol derivative that functions

as an emulsifying agent that makes dietary
lipids soluble in aqueous environment of the
digestive tract
– Approximately one third of cholesterol produced by
liver is converted to bile acids
– Similar to the action of soap in washing process
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 105

 Section 19.11
Emulsification Lipids: Bile Acids

Bile Acids

• Tri- or dihydroxy cholesterol derivatives

• The carbon 17 side chain of cholesterol has
been oxidized to a carboxylic acid
– The oxidized acid side chain is bonded to an amino
acid (either glycine or taurine) through an amide
linkage
• Bile: A fluid containing emulsifying agents
secreted by the liver, stored in the gallbladder,
and released into the small intestine during
digestion
Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 106

Section 19.11
Emulsification Lipids: Bile Acids

Return to TOC

107
Section 19.11
Emulsification Lipids: Bile Acids

Return to TOC

108
Section 19.11
Emulsification Lipids: Bile Acids

LET’S HAVE A BREAK!

Return to TOC

109
 Section 19.11
Emulsification Lipids: Bile Acids

What cholesterol derivative(s) function as a

lipid-emulsifying agent in the aqueous environment
of the digestive tract?

a.Cholic acid
b.12-deoxycholic acid
c.7-deoxycholic acid
d.All of these

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 110

 Section 19.11
Emulsification Lipids: Bile Acids

What cholesterol derivative(s) function as a

lipid-emulsifying agent in the aqueous environment
of the digestive tract?

a.Cholic acid
b.12-deoxycholic acid
c.7-deoxycholic acid
d.All of these

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 111

Section 19.11
Emulsification Lipids: Bile Acids

Return to TOC

112
 Section 19.12
Messenger Lipids: Steroid Hormones

Hormones

• Biochemical substances produced by a ductless

gland that has a messenger function
• Serve as a means of communication between
various tissues
– Some hormones are lipids
• The lipids that play the role of “chemical
messengers” include:
– Steroid hormone - Derivative of cholesterol
– Eicosanoid - Derivative of fatty acids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 113

 Section 19.12
Messenger Lipids: Steroid Hormones

Hormones

• There are two major

classes of steroid
hormones:
– Sex hormones - Control
reproduction and secondary
sex characteristics
– Adrenocorticoid hormones -
Regulate numerous
biochemical processes in
the body

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 114

Section 19.11
Emulsification Lipids: Bile Acids

Return to TOC

115
 Section 19.12
Messenger Lipids: Steroid Hormones

Sex Hormones

• Classified into three major subclasses:

– Estrogens—the female sex hormones

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 116

 Section 19.12
Messenger Lipids: Steroid Hormones

Sex Hormones

• Classified into three major subclasses:

– Androgens—the male sex hormones

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 117

 Section 19.12
Messenger Lipids: Steroid Hormones

Sex Hormones

• Classified into three major subclasses:

– Progestins—the pregnancy hormones

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 118

 Section 19.12
Messenger Lipids: Steroid Hormones

Adrenocorticoid Hormones

• Produced by the adrenal glands

• 28 Different hormones have been isolated from
the adrenal cortex
• Types of adrenocorticoid hormones:
– Mineralocorticoids - Control the balance of Na+ and
K+ ions in cells
– Glucocorticoids - Control glucose metabolism and
counteract inflammation

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 119

 Section 19.12
Messenger Lipids: Steroid Hormones

What are the two large families of lipids that have

messenger functions?

a.Steroid hormones and phospholipids

b.Steroid hormones and eicosanoids
c.Steroid hormones and triacylglycerols
d.Steroid hormones and sphingolipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 120

 Section 19.12
Messenger Lipids: Steroid Hormones

What are the two large families of lipids that have

messenger functions?

a.Steroid hormones and phospholipids

b.Steroid hormones and eicosanoids
c.Steroid hormones and triacylglycerols
d.Steroid hormones and sphingolipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 121

 Section 19.13
Messenger Lipids: Eicosanoids

Eicosanoids

• Arachidonic acid (20:4) derivatives

• Have profound physiological effects at extremely
low concentrations
• Are hormone-like molecules
• Exert their effects in the tissues where they are
synthesized
• Usually have a very short “life”

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 122

 Section 19.13
Messenger Lipids: Eicosanoids

Physiological Effects of Eicosanoids

• Include mediation of:

1. Inflammatory response
2. Production of pain and fever
3. Regulation of blood pressure
4. Induction of blood clotting
5. Control of reproductive functions, such as induction
of labor
6. Regulation of the sleep/wake cycle

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 123

 Section 19.13
Messenger Lipids: Eicosanoids

Principle Types of Eicosanoids

1. Prostaglandin: C20-fatty-acid derivative

containing cyclopentane ring and
oxygen-containing functional groups
– Involved in:
• Raising body temperature
• Inhibiting the secretion of gastric juices
• Increasing the secretion of a protective mucus layer
into the stomach
• Relaxing and contracting smooth muscle
• Directing water and electrolyte balance
• Intensifying pain and enhancing inflammation
responses Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 124

 Section 19.13
Messenger Lipids: Eicosanoids

Principle Types of Eicosanoids

2. Thromboxane: C20-fatty-acid derivative

containing a cyclic ether ring and
oxygen-containing functional groups
̶ Promote platelet aggregation
3. Leukotriene: C20-fatty-acid derivative containing
three conjugated double bonds and hydroxy
groups
– Promote inflammatory and hypersensitivity (allergy)
responses

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 125

 Section 19.13
Messenger Lipids: Eicosanoids

The physiological effects of eicosanoids include

mediation of:

a.the inflammatory response and the regulation of blood

pressure.
b.the production of pain and fever and the regulation of the
sleep/wake cycle.
c.the induction of blood clotting and the control of the
reproductive functions.
d.all the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 126

 Section 19.13
Messenger Lipids: Eicosanoids

The physiological effects of eicosanoids include

mediation of:

a.the inflammatory response and the regulation of blood

pressure.
b.the production of pain and fever and the regulation of the
sleep/wake cycle.
c.the induction of blood clotting and the control of the
reproductive functions.
d.all the above.

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 127

 Section 19.14
Protective-Coating Lipids: Biological Waxes

Biological Wax

• Monoester of a long-chain fatty acid and a

long-chain alcohol
• The fatty acids found in biological waxes:
– Generally saturated fatty acids
– Contain 14 to 36 carbon atoms
• The alcohols found in biological waxes:
– May be saturated or unsaturated
– May contain 16 to 30 carbon atoms

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 128

 Section 19.14
Protective-Coating Lipids: Biological Waxes

What is the chemical makeup of a biological wax?

a.A monoester of a long-chain fatty acid and a short-chain

alcohol
b.A monoester of a short-chain fatty acid and a short-chain
alcohol
c.A monoester of a short-chain fatty acid and a long-chain
alcohol
d.A monoester of a long-chain fatty acid and a long-chain
alcohol

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 129

 Section 19.14
Protective-Coating Lipids: Biological Waxes

What is the chemical makeup of a biological wax?

a.A monoester of a long-chain fatty acid and a short-chain

alcohol
b.A monoester of a short-chain fatty acid and a short-chain
alcohol
c.A monoester of a short-chain fatty acid and a long-chain
alcohol
d.A monoester of a long-chain fatty acid and a long-chain
alcohol

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 130

 Section 19.15
Saponifiable and Nonsaponifiable Lipids

Saponifiable Lipids

• Lipids that undergo hydrolysis in a basic solution

to yield 2 or more small molecules
• Linkage makeup:
– Triacylglycerols—3 ester bonds
– Glycerophospholipids—4 ester bonds
– Sphingophospholipids—1 amide and 2 ester bonds
– Sphingoglycolipids—1 amide, 1 ester, and 1
glycosidic bond
– Biological waxes—1 ester bond

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 131

 Section 19.15
Saponifiable and Nonsaponifiable Lipids

Figure 19.31 - Classification of Lipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 132

 Section 19.15
Saponifiable and Nonsaponifiable Lipids

Which of the following is a nonsaponifiable lipid?

a.Sphingophospholipids
b.Triacylglycerols
c.Steroid hormones
d.Glycerophospholipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 133

 Section 19.15
Saponifiable and Nonsaponifiable Lipids

Which of the following is a nonsaponifiable lipid?

a.Sphingophospholipids
b.Triacylglycerols
c.Steroid hormones
d.Glycerophospholipids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 134

 Chapter 19

Concept Question 1
Triacylglycerols found in animals are solids and are called
fats; however, those found in plants are liquids and are
called oils. What is the structural difference in the
triacylglycerol animal fats and plant oils?

a.Triacylglycerols in fats are composed of unsaturated fatty acids, and

in oils, they are composed of saturated fatty acids.
b.Triacylglycerols in fats are composed of saturated fatty acids, and in
oils, they are composed of unsaturated fatty acids.
c.Fats are triacylglycerol mixtures that are liquid at room temperature,
and oils are triacylglycerol mixtures that are solid at room
temperature.
d.None of the above. Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 135

 Chapter 19

Concept Question 1
Triacylglycerols found in animals are solids and are called
fats; however, those found in plants are liquids and are
called oils. What is the structural difference in the
triacylglycerol animal fats and plant oils?

a.Triacylglycerols in fats are composed of unsaturated fatty acids, and

in oils, they are composed of saturated fatty acids.
b.Triacylglycerols in fats are composed of saturated fatty acids, and in
oils, they are composed of unsaturated fatty acids.
c.Fats are triacylglycerol mixtures that are liquid at room temperature,
and oils are triacylglycerol mixtures that are solid at room
temperature.
d.None of the above. Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 136

 Chapter 19

Concept Question 2

As a result of injury or damage to bodily tissue,

inflammation occurs, which is mediated by _____
that belongs to a class of messenger lipids known
as _____.

a.thromboxanes; steroids
b.prostaglandins; steroids
c.thromboxanes; eicosanoids
d.prostaglandins; eicosanoids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 137

 Chapter 19

Concept Question 2

As a result of injury or damage to bodily tissue,

inflammation occurs, which is mediated by _____
that belongs to a class of messenger lipids known
as _____.

a.thromboxanes; steroids
b.prostaglandins; steroids
c.thromboxanes; eicosanoids
d.prostaglandins; eicosanoids

Return to TOC

Copyright ©2016 Cengage Learning. All Rights Reserved. 138