LOGO
Lecture 7
Lipids
Organic Chemistry – FALL 2015
Course lecturer :
Jasmin Šutković
7 December 2015
CHAPTER OUTLINE
19.1 Introduction to Lipids
19.2 Fatty Acids
19.3 Waxes
19.4 Triacylglycerols—Fats and Oils
19.5 Hydrolysis of Triacylglycerols
19.6 Phospholipids
19.7 Cell Membranes
19.8 FOCUS ON HEALTH & MEDICINE:
Cholesterol, the Most Prominent
Steroid
19.9 Steroid Hormones
19.10 FOCUS ON HEALTH & MEDICINE:
Fat-Soluble Vitamins
19.11 FOCUS ON HEALTH & MEDICINE:
Prostaglandins and Leukotrienes
International University of Sarajevo
Book chapter 19
Introduction
 CHAPTER 19 is the first of four chapters that
deal with the chemistry of biomolecules,
organic molecules found in biological
systems.
 Chapter 19 focuses on lipids, biomolecules that
contain many carbon–carbon and carbon–
hydrogen bonds, making them soluble in organic
solvents and insoluble in water
Introduction
 Lipids are biomolecules that are soluble in
organic solvents and insoluble in water.
 They are found in many varieties, so having
many functions!
 Common lipids include triacylglycerols in
vegetable oils, cholesterol in egg yolk, and
vitamin E in leafy greens.
 The word lipid comes from the Greek
 word lipos for fat.
Lipids
 Basic functions in the body
 Store and provide energy
– Fats provide 9 kcal per gram
 Provide insulation
 Help manufacture steroids and bile salts
 Play a role in transporting fat-soluble nutrients
in the blood
 Used to manufacture major sex hormones
 Key to the structure of cell membranes
Fatty Acids
 Building blocks for triglycerides and
phospholipids
 A chain of carbon and hydrogen atoms
with a carboxyl group at the alpha end and
a methyl group at the omega end
Figure 5.1
Fatty Acids
 Higher ratio of carbon and hydrogen to
oxygen than in carbohydrates and protein
 9 kilocalories per gram of fat
 20 different fatty acids with varied length,
saturation, and shape
Fatty Acids Vary in Length
 Short-chain fatty acids
 Two to four carbons
 Weak attraction
 Liquid at room temperature
 Medium-chain fatty acids
 Six to ten carbons
Fatty Acids Vary in Length
 Long-chain fatty acids




12 or more carbons
Most common type of fatty acid in foods
Strong attraction
Solid at room temperature
Fatty Acids Vary in
Saturation
 Saturated
 All the carbons on the fatty acid are bound to
hydrogen
 Solid at room temperature
 Higher melting point
Fatty Acids Vary in
Saturation
 Unsaturated
 Some carbons on fatty acid form a double
bond with each other instead of binding to
hydrogen
• Monounsaturated fatty acids (MUFA)
– Has one double bond
• Polyunsaturated fatty acid (PUFA)
– Has two or more double bonds
 Liquid at room temperature
 Lower melting point
Saturated and Unsaturated Fatty Acids
Help Shape Foods
Figure 5.3
Fatty Acids Differ in
Double-Bond Location
 The location of the first double bond in
unsaturated fatty acids effect the omega-3
fatty acid and omega-6 fatty acid
 Omega-3 fatty acid
 First double bond is between the third and
fourth carbon from the omega end
 Example: Alpha-linolenic acid
• One of the two essential fatty acids
Fatty Acids Differ in
Double-Bond Location
 Omega-6 fatty acid
 First double bond is between the sixth and
seventh carbon from the omega end
 Example: Linoleic acid
• One of the two essential fatty acids
The Omega Fatty Acids
Figure 5.4
Fatty Acids Vary in Shape
 Unsaturated fatty acids form two different
shapes
Figure 5.5
Triglycerides
 Three fatty acids connected to a glycerol
backbone
Portion of Figure 5.7
Triglycerides
 Most common lipid in both foods and the body
 Make up about 95% of lipids found in foods
 Functions




Add texture
Makes meats tender
Preserves freshness
Stores as adipose tissue
for energy
Caution:
High levels
in the blood
are a risk
factor for
heart
disease
Phospholipids
 Hydrophilic on one end; hydrophobic on the other
 Make up the phospholipid bilayer in the cell membrane
 Synthesized by the liver
Portion of Figure 5.8
Phospholipids’ Role in Cell
Membranes
Figure 5.9
Sterols
 More complex than phospholipids or triglycerides
 Four connecting rings of carbon and hydrogen
 Do not provide energy
 Cholesterol is the best known sterol
 Found in every cell in the body
 Helps with numerous body processes
 Phytosterols – major plant sterols
Figure 5.11
Quick Review
Figure 5.12
Quick Review
 Triglycerides
 Found in the body
 Stored in the adipose tissue
 Major source of energy
 Phospholipids
 An important part of cell membrane structure
 Lecithin
• Important to cell membrane
• Used as a food emulsifier
 Sterols
 Do not contain fatty acids
 Do not provide energy
What Happens to the Lipids
You Eat?
 Lipids from foods
 Fat, phospholipids, and sterols
 Digested to
 Free fatty acids, glycerol, and monoglycerides
 With the aid of the enzyme lipase
Figure 5.13
Figure 5.13
Figure 5.13
Most Fat Is Digested
and Absorbed in the
Small Intestine
Lipoproteins Transport Fat
Through the Lymph and Blood
 Lipoproteins (transporter proteins)




Chylomicrons
Very low-density lipoproteins (VLDLs)
Low-density lipoproteins (LDLs)
High-density lipoproteins (HDLs)
Lipoproteins Transport Fat Through the
Lymph and Blood
 VLDLs, LDLs, and HDLs
 Globular molecule with a lipid center surrounded
by a plasma membrane
 Density determines function
 More protein, higher density
 Very low-density lipoproteins (VLDLs)
 Become LDLs
 LDLs: “bad” cholesterol
 HDLs: “good” cholesterol
 HDL and LDL levels can be used to determine the
health of arteries
The Roles of VLDL, LDL, and HDL Lipoproteins
Figure 5.18
Uses of Fat and Cholesterol
 Source of energy
 Form body structures
 Regulate metabolism
 Enhance absorption of fat-soluble vitamins
 Provide insulation to help regulate body
temperature
 Cushion major organs
Fat Is Used as Energy
 Fat
 Provides concentrated source of kilocalories
• 9 kilocalories per gram
 Readily available when the body needs energy
 Body’s main source of energy throughout the
day
Fat Is Used as Energy
 Fat
 Body has an unlimited ability to store excess
energy as fat in adipocytes
• Fat cells have the capacity to enlarge as much as
1,000 times their original size
• Body has the ability to produce additional fat cells
Fat Is Used as Energy and
Helps Absorb Lipid Compounds
 Preferred source of energy for the heart, liver, and muscles
 Cannot sustain life alone
 Needs glucose
 Only glycerol can be used for gluconeogenesis
 Several essential nutrients require dietary fat for absorption
 20 grams per day are needed to stimulate chylomicrons that
transport fat-soluble vitamins
Fat Helps Insulate and
Protect
 Fat in subcutaneous tissue
 Insulates body
 Maintains body temperature
 Fat protects bones and vital organs from
trauma
 Too much fat eliminates the protective benefit
Cholesterol Is Used to Make
Bile, Hormones, and Vitamin D
 Cholesterol




A structural part of the cell membrane
A precursor to vitamin D
A precursor to bile acid
Precursor for sex hormones such as estrogen and
testosterone
How Much Fat Do We Need
Each Day?
 Overall intake of fat in the U.S. is higher
than it should be
 Acceptable Macronutrient Distribution
(AMDR) recommendation
 20–35% of daily kilocalories should come from
fat
 For heart health
 Consume no more than 10% of total
kilocalories from saturated fat
 Limit trans fats to < 1%
Essential Fatty Acid
Recommendations
 Adequate Intake (AI) for the essential fatty acids
 Alpha-linolenic acid
• Men
• Women
1.6 grams/d
1.1 grams/d
 Linoleic acid
• Men
• Women
17 grams/d
12 grams/d
*Currently Americans only consume about 0.1–0.2 grams/d of EPA
and DHA
Sources of unsaturated fats 
Best Food Sources of Fat
Figure 5.20
Food Sources of Omega-3
Fatty Acids
Figure 5.21
Where’s the Saturated Fat in
Foods?
Figure 5.22
What Is Heart Disease and
What Factors Increase Risk?
 Cardiovascular disease is the number-one
killer of adults in the world…
Fat and
Cholesterol
Accumulate
in the
arteries
Arteries
narrow
Blood flow
is impeded
Decrease
oxygen
and
nutrients
• Not
enough
oxygen to
the heart
• CHEST
PAIN
Atherosclerosis
Figure 5.24
For a healthy life do….
 For optimal long-term health a diet should include a
proper balance of all nutrients including fat
 There are different types of lipids, some essential and
others not required from foods
 Goal
 Consume mostly unsaturated fats
 Limit amount of saturated and trans fats
 A plant-based diet plentiful in whole grains, fruits, and
vegetables, with some low-fat dairy and lean meats,
poultry, fish, and vegetable oil will be high in fiber and
lower in saturated fats, trans fats, and dietary cholesterol
Types of lipids
 Lipids can be categorized as hydrolyzable or nonhydrolyzable.
Two types of fatty acids :
 Saturated fatty acids have no double bonds
in their long hydrocarbon chains.
 Unsaturated fatty acids have one or more
double bonds in their long hydrocarbon
chains. Generally, double bonds in naturally
occurring fatty acids are cis.
WAXES
 Waxes are the simplest hydrolyzable lipids.
 Waxes are esters (RCOOR') formed from a fatty acid
(RCOOH) and a high molecular weight alcohol
(R'OH).
 Because of their long nonpolar carbon chains, waxes are
very hydrophobic.
 They form a protective coating on the feathers of birds to
make them water repellent, and on leaves to prevent
water evaporation.
 Lanolin is a wax thatcoats the wool fibers of sheep.
 Beeswax, a complex mixture of over 200 different
compounds, contains the wax myricyl palmitate as its
major component
TRIACYLGLYCEROLS—FATS
AND OILS
 Animal fats and vegetable oils, the most
abundant lipids, are composed of
triacylglycerols
 Triacylglycerols, or triglycerides, are
triesters formed from glycerol and three
molecules of fatty acids.
PHOSPHOLIPIDS
 Phospholipids are lipids that contain a phosphorus atom.
 Two common types of phospholipids are phosphoacylglycerols
and sphingomyelins.
 Both classes are found almost exclusively in the cell membranes of
plants and animals .
Phosphoacylglycerols
 Phosphoacylglycerols (or phosphoglycerides) are the
second most abundant type of lipid.
 They form the principal lipid component of most cell
membranes.
SPHINGOMYELINS
 Sphingomyelins, the second major class of
phospholipids, differ in two important ways from the
triacylglycerols and the phosphoacylglycerols.
1. Sphingomyelins do not contain a glycerol backbone.
Instead, sphingomyelins are derived from
sphingosine.
2. Sphingomyelins do not contain an ester. Instead,
their single fatty acid is bonded to the carbon
backbone by an amide bond.
Cholesterol – most abudant
steroid
 Steroids are lipids whose carbon skeletons contain three
six-membered rings and one five membered ring.
Fat soluble vitamins
 The fat-soluble vitamins are lipids.
 The four fat-soluble vitamins—A, D, E, and K—are found in fruits
and vegetables, fi sh, liver, and dairy products. Although fat-soluble
vitamins must be obtained from the diet, they do not have to be
ingested every day.
 Excess vitamins are stored in adipose cells, and then used when
needed.
 Table 19.5 summarizes the dietary sources and recommended daily
intake of the fatsoluble vitamins.
Few topics for the coming
projects…
 Saturates and unsaturated fats in our food
 Biofuels
 Cell membrane structure
 Transport across the cell membrane
 Cholesterol and Lipoproteins
 Steroid hormones
 Asthma – steroids and leukotriens?
Short guidelines…
 Power point presentation 4%
 8 to 15 slides
 Written Paper 4%
 10 pages (double space: Introduction, main
body and conclusion, don’t forget reference
and citations)
 Answering of my and your colleagues
questions 2%
 Presentation week: 4 i 6th January 2016
Readings
 Chapter 19 – pages : 569 -610
 14th Dec.2014 Quiz II :Only lectures 6, 7 and 8 !
 Read the book and dont forget to start to
think about your projects- select a topic by
21th December or I will find it for You…