Lecture 3:
Lipids: Fats, Phospholipids, Steroids
1
Yesterday’s Exit Ticket
Macromolecule
Monomer or
Types
Function(s)
Key Element(s)
(e.g. carbon)
Carbohydrates
Monosaccharide
Energy supply
C, H, O
Lipids
Fats, Steroids,
Phospholipids
Energy storage, C, H
hormones, cell
membranes
Proteins
Amino acid
Just about
everything…
C, H, O, N
Nucleic Acids
Nucleotide
Information
storage and
transmission
C, H, O, N, P
• What element(s) (i.e. atom types) do all 4
molecules have in common?
– C and H: they are all organic molecules!
2
Key Themes
(2) “Think Like a Biologist”: Understand What Life Is.
“Unity” of life: What are the common features of all life?
• Structure and function of the molecules of life
3
The Basics: General properties of lipids
1. Lipids are macromolecules,
but technically not polymers
No long chains of many repeated subunits
4
We will discuss three lipid classes:
Fats
Phospholipids
Steroids
Mostly hydrophobic
http://wiki.faithlutheranlv.org/groups/carmanbio/wiki/
dbc5b/Lipids.html
5
We will discuss three lipid classes:
Fats
Phospholipids
Steroids
Fat = glycerol + 3 fatty acid chains
6
How is a fat constructed?
From glycerol + fatty acids
Removal of H2O
(dehydration
synthesis)
Fig. 5.11
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How is a fat constructed?
From glycerol + fatty acids
Removal of H2O
(dehydration
synthesis)
Fig. 5.11
forms new bond
between glycerol &
fatty acid
Fat with 3 fatty acids
= triacylglycerol
= triglyceride
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Fats
• Fats are constructed from two types of
smaller molecules: glycerol and 3 fatty
acids
http://www.colorado.edu/ebio/genbio/05_11Fats_A.html
(end when box turns orange)
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Energy storage in fat versus carbohydrate
• Carbohydrates = 4 kcal/gram
• Proteins = 4 kcal/gram
• Fats = 9 kcal/gram
I
H - C - OH
I
“Carb”
(CHOH)n
(CH”R”)n
(CH2)n
I
H-C-H
I
Fat
Gram-for-gram, fats store twice as much energy
as carbohydrates and proteins
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Fat is used to store energy when a compact energy
source with minimum weight is needed.
What organisms (or stages of organisms) would you
predict to store fats (rather than polysaccharides)?
11
Functions of dietary fats
• Energy supply (all fats)
• Building blocks for body (omega-6 & omega-3
fatty acids needed for brain / heart muscle …)
• Diet-gene interaction (omega-6 & omega-3
fatty acids converted to hormone messengers)
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http://www.colorado.edu/ebio/genbio/05_11Fats_A.html
Saturated – single bonds – straight – solid
Unsaturated – double bonds – L-shaped – liquid
13
http://spaceflight.esa.int/impress/text/education/
Glossary/Glossary_T.html
Which of the fats below (all with the same number of
carbon atoms) has the highest energy content?
A) a fat composed of saturated fatty acids
B) a fat composed of monounsaturated fatty acids
C) a fat composed of polyunsaturated fatty acids
Think-Pair-Share
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Saturated and Unsaturated Fats
How can you tell them apart?
Saturated fats are solid
Unsaturated fats are liquid
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Real World Connection:
Saturated and Unsaturated Fats in the News
Which is better for your health?
Consumption of saturated
fats raises cholesterol
levels.
Most of the cholesterol in
human body is synthesized
from saturated fats!
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Stearic acid
a) Saturated fatty acid
Oleic acid
(b) Monounsaturated
fatty acid (MUFA)
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MUFA
Mono Unsaturated Fatty Acid
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http://wiki.faithlutheranlv.org/groups/carmanbio/wiki/dbc5b/Lipids.html
Recommended changes to current US diet:
Reduce saturated fats.
Increase monounsaturated fats.
Oleic acid
Stearic acid
(a) Saturated fatty acid
Fig. 5.12
(b) Monounsaturated
fatty acid (MUFA)
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http://instruct.westvalley.edu/svensson/Cells/07molecules.htm
20
Recommended changes cont:
Reduce omega-6 polyunsaturated fatty acids (PUFAs).
Increase omega-3 PUFAs.
Difference between Omega-3 and Omega-6 PUFAs
http://www.supplementquality.com/news/fatty_acid_structure.html
(Note that all PUFAs are highly “kinked”,
even though the simple image on the right does not reflect this.)
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saturated
monounsaturated
polyunsaturated
A saturated fat is saturated with the maximal
number of
http://spaceflight.esa.int/impres
A) carbon atoms (C).
s/text/education/Glossary/Glos
sary_T.html
B) hydrogen atoms (H).
C) C=C bonds.
D) carbon and hydrogen atoms.
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E) hydrogen atoms and C-H bonds.
Think-Pair-Share
http://sabrebrains.blogspot.com/2011/02/lipids.html
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Predict the result(s) of removing hydrogen atoms
from the fatty acid tails of saturated animal fat
(lard):
A) The number of carbon-carbon double bonds in
the fat molecules increases.
B) The number of carbon-carbon double bonds in
the fat molecules decreases.
C) The fat becomes more fluid.
D) A and C
E) B and C
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Think-Pair-Share
Latest recommendation for ideal fat
composition in the human diet:
70-80% monounsaturated fatty acids
10-15% polyunsaturated fatty acids
(omega-6 to omega-3 ratio 2:1)
10-15% saturated fatty acids (animal)
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10-15%
10-15%
70-80%
Ratio of ≤2 to 1
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http://www.canola-council.org/canola_resources/product45.aspx
Polyunsaturated Fatty Acids (PUFAs) = Essential Fatty Acids (EFAs)
Why a 2:1 ratio?
Omega-6
Omega-3
Converted to hormones
that speed up cell division
and trigger inflammation
Converted to hormones
that slow down cell division
and dampen inflammation
Healthy, balanced ratio of omega-6 to omega-3 fatty acids
is 2:1,
whereas estimate for modern US diet is 20:1
= highly unbalanced
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Polyunsaturated Fatty Acids = Essential Fats
Omega-6
Omega-3
(LA, linoleic acid)
Lots in corn, sunflower, soybean oil
(ALA, alpha-linolenic acid)
In flax seed, nuts, canola oil
(AA)
In meat, milk of grain-fed cattle
EPA and DHA
In fatty fish
Converted to hormones
that speed up cell division
and trigger inflammation
Converted to hormones
that slow down cell division
and dampen inflammation
28
The Yin & Yang of Inflammation
The “GOOD”: Upon injury/infection, proinflammatory prostaglandins “call” white
blood cells to engulf & destroy injured
body cells & invaders.
The “BAD”: Overproduction of proinflammatory messengers causes white
blood cells to attack uninjured body cells.
29
http://taoism.about.com/od/visualsymbols/ig/Taoist-Symbols/Yin-Yang-Symbol.--jj.htm
Impact of dietary fats
on human health
Modern western diet
High saturated fat
High omega-6:3 fatty
acid ratio
Healthful diet
Chronic
PROMOTE disease PREVENT
and
disorders
Low saturated fat
Balanced
omega-6:3 fatty acid
ratio
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Just FYI: Real World Advice
Good source of omega-3
fatty acids,
± low in mercury & PCBs
•
•
•
•
•
•
•
•
Salmon (wild, farmed?)
Mackerel (but not king mackerel!)
Mussels, oysters
Anchovies
Rainbow trout
Herring
Sardines
Tuna (but not bluefin, white/albacore?)
Stay away from
Highly mercury contaminated
fish (>1 ppm)
Shark
Swordfish
King mackerel
Tilefish
And also
Bluefin tuna
Chilean sea bass
Rockfish
Grouper
Bluefish
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http://www.montereybayaquarium.org/cr/cr_seafoodwatch/download.aspx
Which is correct?
A) omega-3 fatty acids are good and omega-6 fatty acids
are bad
B) omega-6 fatty acids have no positive effects
A) both omega-3 fatty acids and omega-6 fatty acids
have vital roles in the human body
D) the ratio of omega-6 to omega-3 fatty acids is not
important for human health
E) B, C, and D are all correct
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5 minute break
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blog.famasalescoffee.com
Three types of lipids:
Fats
Phospholipids
Steroids
Phospholipid = phosphate + glycerol + 2 fatty acid
chains
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How is a phospholipid constructed?
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Fig. 5.13
How is a phospholipid constructed?
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Fig. 5.13
A phospholipid is shown below. Predict which of the
structures A-D, also shown below, is MOST LIKELY
to form when a phospholipid is dispersed in water.
hydrophilic (water-loving) polar head group
hydrophobic (water-fearing) non-polar tails
A.
B.
H20
H20
H20
C.
H20
H20
D.
H20
H20
H20
Think-Pair-Share
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Interactions of phospholipid molecules with water
The basis of phospholipid bilayers
Hydrophilic
head
Hydrophobic
tail
WATER
WATER
Fig. 5.14
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Structure-function relationship:
Phospholipids are key to the existence of biological cells
Hydrophilic
head
Hydrophobic
tail
WATER
WATER
Fig. 5.14
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Phospholipid
Fa
t
Fig. 5.11
Fig. 5.13
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(Three types of lipids:)
Fats
Phospholipids
Steroids
Steroids = 4 carbon-hydrogen rings
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http://www.uv.es/EBRIT/macro/m
acro_5009_2_284.html
http://www.sciencephoto.com/media/97627/enlarge
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Steroids: What are they?
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pictureschat.com; ellies-whole-grains.com; medicalinsider.com; genesistraining.org.uk
Sex hormones are steroids.
Fig. 4.9
Estradiol
(an estrogen)
Testosterone
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See pages 977 & 993-994 in textbook for more information
Made from saturated dietary fat
Fig. 5.15
Cholesterol
• Has a role in heart disease (will be visited later)
• Stabilizes biological membranes in animals (will be visited later)
• Is an important precursor for other steroids
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Roles of cholesterol
Fig. 5.15
Precursor in synthesis of:
Sex hormones, stress hormones, Vitamin 46D
Synthesis of steroid stress hormones
(corticosteroids) from cholesterol
http://www.neurosci.pharm.utoledo.edu/MBC3320/steroid_hormones.htm
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How does eating NO saturated fats
negatively affect your health?
a) It wouldn’t. Saturated fats are bad.
b) It would reduce sex hormones, but who
wants to be hormonal anyway?
c) It would reduce steroid hormones, so
the body is less muscular.
d) It would reduce sex hormones, and
there are negative effects of this.
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Roles of cholesterol
Fig. 5.15
Precursor in synthesis of:
Sex hormones, stress hormones, Vitamin 49D
+ UV
Cholesterol
http://en.wikipedia.org/wiki/Vitamin_D
Vitamin 50
D2
Which lipid is most hydrophilic?
Fats
Phospholipids
Fig. 5.15
Steroids
Fig. 5.11
Fig. 5.13
“Water and oil don’t mix!”
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Fats
Phospholipids
Fig. 5.15
Steroids
Fig. 5.11
Fig. 5.13
What are the roles of these lipids?
Energy supply?
Cellular building blocks?
Hormone-like messengers?
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Today’s Exit Ticket
• Describe the key differences between:
– Saturated fats
– Monounsaturated fats
– Polyunsaturated fats
• Give an example of each that you have
consumed in the last week
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