1. Chapter 1 - Three Societies on the Verge of Contact
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2. Learning Outcomes
List and describe the major types, functions, and structures of lipids.
Differentiate among essential, conditionally essential, and nonessential fatty acids.
Describe the differences among mono-, di-, and triglycerides.
Discuss the functions of phospholipids and sterols.
Explain the processes of triglyceride digestion, absorption, and circulation.

3. Learning Outcomes
6 List and describe the types and functions of the various lipoproteins. 7 Explain the impact of lipids on your health. 8 Understand and be able to implement dietary recommendations for lipids.

4. Organic macronutrients
What Are Lipids?
Organic macronutrients
Insoluble in water
Hydrophobic
Roles of lipids
Oil
Liquid at room temperature
Fat
Solid at room temperature
Major lipids

5. What Are Lipids? Fatty acids
Most abundant type of lipid in body and diet
Structure
Carbon chain
Alpha end – carboxylic acid group
Omega end – methyl group
Types
Number of carbons
Types and locations of chemical bonds

6. FIGURE 6.1 Fatty Acid Structure
All fatty acids have three components: a methyl or ω end (–CH3), a fatty acid backbone
made from carbon and hydrogen atoms and a carboxylic acid or α end (–COOH). 6

7. What Are Lipids? Fatty acids Chain length
Most naturally-occurring fatty acids have even number
Short-chain, medium-chain, and long-chain fatty acids
Chemical properties
Physiological functions
Solubility in water

8. FIGURE 6.2 Fatty Acids Can Have Different Chain Lengths
First image: Medium-chain fatty acid
Second Image: Long-chain fatty acid 8

9. What Are Lipids? Fatty acids Chemical bonds Single bonds Double bonds
Saturated fatty acids (SFAs)
Double bonds
Monounsaturated fatty acids (MUFAs)
Polyunsaturated fatty acids (PUFAs)
Chemical nature

10. FIGURE 6.3 Saturated and Unsaturated Fatty Acids
First image: Saturated fatty acid - This double bond is part of the
carboxylic acid group and does not
make the fatty acid “unsaturated.”
Second image: Monounsaturated fatty acid - The presence of a double bond
bends the fatty acid backbone. There are two fewer hydrogens for each double bond.
Third image: Polyunsaturated fatty acid - The presence of two
double bonds causes
two bends in the fatty
acid backbone.
The type of carbon–carbon bonds in a fatty acid determines whether it is saturated
or unsaturated. 10

11. What Are Lipids? Fatty acids Cis double bonds
Hydrogens on same side of double bond
Trans double bond
Hydrogens on opposite sides of double bond
Trans fatty acids in food
Naturally occurring
Hydrogenation

12. FIGURE 6.4 Cis versus Trans Fatty Acids
First image: A cis fatty acid - Hydrogens are on the same
side of the fatty acid backbone.
Second image: A trans fatty acid - Hydrogens are on opposite
sides of the fatty acid backbone.
Unsaturated fatty acids differ according to whether
they have cis or trans carbon–carbon double bonds.
cis bonds cause the fatty acid to bend, whereas trans
bonds do not. 12

13. What Are Lipids? Naming fatty acids Characteristics
Alpha naming system
Relative to carboxylic acid end
Omega naming system
Double bond’s distance from the methyl end
Omega-3 and omega-6 fatty acids
Common names

14. FIGURE 6.5 The Alpha (α) Naming System
The first double bond (which is
cis) from the alpha end is on the
ninth carbon atom.
The second double bond
(which is cis) from the alpha
end is on the twelfth carbon atom.
The alpha naming system for fatty acids requires that you count how far the double
bonds are from the alpha (carboxylic acid) end of the carbon backbone. Using this
system, this fatty acid’s name is cis9, cis12–18:2. 14

15. What Are Essential, Conditionally Essential, and Nonessential Fatty Acids?
Linoleic acid
18 carbons; two double bonds; omega-6 fatty acid
Arachidonic acid
Linolenic acid
18 carbons; three double bonds; omega-3 fatty acid
EPA
DHA

16. What Are Essential, Conditionally Essential, and Nonessential Fatty Acids?
Eicosanoids
Roles
Omega-6 eicosanoids
Cause inflammation and constriction of blood vessels
Omega-3 eicosanoids
Reduce inflammation and stimulate dilation of blood vessels

17. FIGURE 6.6 Fatty Acid Metabolism and Eicosanoid Formation
1. The essential fatty acids can be
elongated and desaturated to form
new fatty acids such as arachidonic
acid, EPA, and DHA.
2. Arachidonic acid and EPA can
be further metabolized to 􀁚-6
and 􀁚-3 eicosanoids, respectively.
Note that eicosanoids are not,
themselves, fatty acids.
Linoleic acid and linolenic acid can be converted, via elongation and desaturation, to longer-chain polyunsaturated
fatty acids, some of which are used to make hormone-like eicosanoids. 17

18. What Are Essential, Conditionally Essential, and Nonessential Fatty Acids?
Deficiency
Primary
Rare
Secondary
Diseases that disrupt lipid absorption
Cystic fibrosis
People who consume foods high in v-3 fatty acids
(such as many cold-water fish) may have lower risk
for conditions related to inflammation, such as heart
disease.

19. Conditionally essential fatty acids
What Are Essential, Conditionally Essential, and Nonessential Fatty Acids?
Conditionally essential fatty acids
Infancy
Arachidonic acid
DHA
Dietary sources of fatty acids
Linoleic acid
Linolenic acid
EPA and DHA

20. Nonessential fatty acids
What Are Essential, Conditionally Essential, and Nonessential Fatty Acids?
Nonessential fatty acids
Dietary sources
SFAs
PUFAs
MUFAs
Roles

21. What Is the Difference between Mono-, Di-, and Triglycerides?
Number of fatty acids in chemical structure
Saturation of fatty acids
Lipogenesis
Fatty acids combine with glycerol

22. FIGURE 6.8 Triglyceride Structure
These fatty acids
can be saturated (SFA),
monounsaturated (MUFA),
polyunsaturated (PUFA),
or a combination.
A triglyceride consists of a glycerol molecule and three
fatty acids. 22

23. What Is the Difference between Mono-, Di-, and Triglycerides?
Richest source of energy
9 kcal per gram
Lipolysis
β-oxidation
Ketones
Ketogenesis

24. What Is the Difference between Mono-, Di-, and Triglycerides?
Storage in adipose tissue
Adipocytes
Stored as triglycerides
Advantages
Location of adipose tissue
Subcutaneous vs. visceral adipose tissue
Role of insulin
Insulation

25. What Are Phospholipids and Sterols?
Roles
Cell membranes
Transport of lipids in bloodstream
No dietary requirements for either of them

26. What Are Phospholipids and Sterols?
Has two fatty acids
Phosphate-containing hydrophilic head
Amphipathic
Roles
Cell membranes
Digestion, absorption, and transport of lipids
Other functions

27. FIGURE 6.10 Cell Membrane Made from Phospholipid Bilayer
Proteins are
embedded in the
cell membrane.
Cell membranes are
made of a bilayer of
phospholipids with
proteins and
cholesterol dispersed.
Hydrophobic fatty
acids make up the
interior portion of
the cell membrane.
Hydrophilic head groups
point toward hydrophilic
(watery) environments.
The amphipathic nature of phospholipids allows cell membranes to carry out their functions. 27

28. What Are Phospholipids and Sterols?
Multi-ring structure
Cholesterol
Synthesis of bile acid
Component of cell membranes
Reproductive hormones
Other roles
Sources
Phytosterols

29. FIGURE 6.12 Cholesterol Content of Selected Foods
Source: USDA National Nutrition Database for Standard Reference, Release 18, 2005. 29

30. How Are Triglycerides Digested, Absorbed, and Circulated?
Basic goal of digestion
Mouth
Lingual lipase
Stomach
Gastrin
Gastric lipase

31. How Are Triglycerides Digested, Absorbed, and Circulated?
Small intestine
Phase 1: Micelle formation
Bile disperses large globules into smaller droplets
Emulsification
Gallbladder disease
Removal of gallbladder

32. FIGURE 6. 14. Emulsification of Lipids to Form
FIGURE Emulsification of Lipids to Form Micelles in the Small Intestine
The liver produces
bile, which contains
bile acids, cholesterol,
and phospholipids.
The gallbladder
stores the bile and
releases it into the
small intestine.
Emulsification
occurs in the
1. Large lipid globules
made of fatty acids,
monoglycerides,
diglycerides,
triglycerides, and
cholesterol enter the
small intestine
from the stomach.
2. The presence of
lipids in the small
intestine stimulates
the release of
cholecystokinin
(CCK). CCK signals
the gallbladder to
release bile, which
consists of bile
acids, cholesterol,
3. Bile acids and phospholipids
emulsify
the fat globules by
breaking them into
smaller particles,
called micelles, and
stabilizing them in
the small intestine.
Intestinal emulsification of lipids requires bile acid- and phospholipid-containing bile, which is produced in the liver
and stored in the gallbladder. 32

33. How Are Triglycerides Digested, Absorbed, and Circulated?
Small intestine
Phase 2: Pancreatic lipase
Secretin
Release of pancreatic lipase
Final products of lipid digestion
Fatty acids
Glycerol
Monoglycerides

34. How Are Triglycerides Digested, Absorbed, and Circulated?
Absorption
Two ways
Unassisted transport into intestinal cells
Short- and medium-chain fatty acids
Repackaging into micelles in lumen
Contents released into intestinal cell’s interior

35. How Are Triglycerides Digested, Absorbed, and Circulated?
Circulation
Depends on hydrophilic nature of lipid
More hydrophilic
Circulation in blood attached to albumin
Circulates to liver
Less hydrophilic
Circulated in lymph
Lipoproteins
Liporotein lipase

36. FIGURE 6.15 Absorption and Circulation of Lipids
1. Short- and medium-chain
fatty acids are absorbed
easily and circulated,
bound to albumin, in the
blood to the liver.
2. Long-chain fatty acids, phospholipids,
cholesterol, and monogylcerides are
packaged into micelles and then taken
up by the intestinal cell.
3. Triglycerides and phospholipids
are reformed.
4. Triglycerides, cholesterol and
phospholipids are then
packaged into chylomicra and
circulated in the lymph.
The process by which a lipid is absorbed and circulated depends on how hydrophilic it is. In general, it is easier for the body
to absorb and circulate hydrophilic lipids (like short-chain fatty acids) than hydrophobic ones (like long-chain fatty acids). 36

37. What Are the Types and Functions of Various Lipoproteins?
Produced in the liver
Transport lipids in the blood
Complex globular structures
Apoprotein
Chylomicron
Largest and least dense
Produced in small intestine
Transport dietary lipids exclusively

38. FIGURE 6.17 Origins and Major Functions of Lipoproteins
Lipoproteins -- The liver makes very-low-density
lipoproteins (VLDL). Major functions -- VLDLs transport endogenous and
exogenous fatty acids from the
liver to the body with the help of
lipoprotein lipase.
Lipoproteins -- Intermediate-density
lipoproteins (IDL). Major functions -- IDLs continue to deliver dietary
and other fatty acids to the
body. Some are also taken up
by the liver.
Lipoproteins -- Low-density lipoproteins (LDL). Major functions -- LDLs deliver cholesterol to the
body (especially liver, adipose,
and muscle cells) by docking with
LDL receptors located on the
cell membranes of receptive cells.
Lipoproteins -- The liver and small
intestine make high-density
lipoproteins (HDL). Major functions -- HDLs pick up (scavenge) excess
cholesterol from nonhepatic
(nonliver) cells and deliver it to
the liver. This is called “reverse
cholesterol transport.”
Lipoproteins -- The small intestine
makes chylomicra. Major functions -- Chylomicra deliver exogenous
dietary fatty acids to the body
with the help of llipoprotein lipase.
Both the liver and small intestine make lipoproteins that circulate lipids in the body. 38

39. What Are the Types and Functions of Various Lipoproteins?
Very low-density lipoprotein (VLDL)
Lower lipid-to-protein ratio than chylomicra
Primary function
Low-density lipoproteins (LDL)
LDL receptors
“Bad” cholesterol
Plaque
Intermediate-density lipoprotein (IDL)

40. What Are the Types and Functions of Various Lipoproteins?
High-density lipoproteins (HDL)
Lowest lipid-to-protein ratio
Collect excess cholesterol
Transport it back to the liver
“Good” cholesterol
Different types
Not equally effective in removing cholesterol

41. How Are Dietary Lipids Related to Health?
High-fat foods and obesity
Major public health concern
Associated health risks
Although consumption of a high-fat diet can increase
risk for obesity, there are many other factors, such as
genetics and inadequate exercise, that contribute to
this health problem.

42. How Are Dietary Lipids Related to Health?
Cardiovascular disease
Common types
Heart disease
Stroke
Atherosclerosis
Blood clot
Aneurysm
Lipids of concern
Genetics

43. FIGURE 6.18 Causes of Cardiovascular Disease
Healthy blood vessel: Healthy arteries
allow adequate
blood flow.
Atherosclerotic plaque, Blood clot, or Ruptured
Aneurysm: Anything that
reduces or
blocks blood
flow can cause
cardiovascular
disease.
Atherosclerosis, blood clots, and aneurysms can all reduce or stop blood flow, leading
to cardiovascular disease. 43

44. How Are Dietary Lipids Related to Health?
Cardiovascular disease
Nutritional guidelines
Moderate overall energy intake
Balance your macronutrients
Whole grains
Dietary fiber
Cancer
Recommendations

45. What Are Some Overall Dietary Recommendations for Lipids?
Essential fatty acids
Consume adequate amounts
DRIs
AIs
Omega-3 fatty acid intake
Limit cholesterol, SFAs, and trans fat
Dietary guidelines
Total lipid consumption
AMDRs

46. FIGURE 6.19 Reading Nutrition Facts Panels
You can tell how much total fat, saturated fat, and
trans fat is in a food by checking its Nutrition Facts
panel. 46