Lecture 3:Lipids: Fats, Phospholipids, Steroids
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Yesterday’s Exit Ticket
• What element(s) (i.e. atom types) do all 4 molecules have in common?– C and H: they are all organic molecules!
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, hormones, cell membranes
C, H
Proteins Amino acid Just about everything…
C, H, O, N
Nucleic Acids Nucleotide Information storage and transmission
C, H, O, N, P
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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
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The Basics: General properties of lipids
1. Lipids are macromolecules, but technically not polymers
No long chains of many repeated subunits
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We will discuss three lipid classes:FatsPhospholipidsSteroids
http://wiki.faithlutheranlv.org/groups/carmanbio/wiki/dbc5b/Lipids.html
Mostly hydrophobic
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We will discuss three lipid classes:FatsPhospholipidsSteroids
Fat = glycerol + 3 fatty acid chains
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Removal of H2O(dehydration synthesis)
Fig. 5.11
How is a fat constructed? From glycerol + fatty acids
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Removal of H2O(dehydration synthesis)
forms new bond between glycerol & fatty acid
Fat with 3 fatty acids= triacylglycerol= triglyceride
Fig. 5.11
How is a fat constructed?From glycerol + fatty acids
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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
Gram-for-gram, fats store twice as much energy as carbohydrates and proteins
• Carbohydrates = 4 kcal/gram (CHOH)n
• Proteins = 4 kcal/gram (CH”R”)n
• Fats = 9 kcal/gram (CH2)n
I H - C - OH
I“Carb”
I H - C - H
I Fat
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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)?
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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 – solidUnsaturated – double bonds – L-shaped – liquid
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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 acidsB) a fat composed of monounsaturated fatty acidsC) a fat composed of polyunsaturated fatty acids
Think-Pair-Share
http://spaceflight.esa.int/impress/text/education/Glossary/Glossary_T.html
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Saturated and Unsaturated Fats
Saturated fats are solid
Unsaturated fats are liquid
How can you tell them apart?
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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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a) Saturated fatty acid
Stearic acid
(b) Monounsaturated fatty acid (MUFA)
Oleic acid
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http://wiki.faithlutheranlv.org/groups/carmanbio/wiki/dbc5b/Lipids.html
MUFA
Mono Unsaturated Fatty Acid
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(a) Saturated fatty acid
Stearic acid
(b) Monounsaturated fatty acid (MUFA)
Oleic acid
Fig. 5.12
Recommended changes to current US diet:
Reduce saturated fats.
Increase monounsaturated fats.
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http://instruct.westvalley.edu/svensson/Cells/07molecules.htm20
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.)
Recommended changes cont:
Reduce omega-6 polyunsaturated fatty acids (PUFAs).
Increase omega-3 PUFAs.
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A saturated fat is saturated with the maximal number of A) carbon atoms (C).B) hydrogen atoms (H).C) C=C bonds.D) carbon and hydrogen atoms.E) hydrogen atoms and C-H bonds.
Think-Pair-Share
http://spaceflight.esa.int/impress/text/education/Glossary/Glossary_T.html
saturated
monounsaturated
polyunsaturated
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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 CE) B and C
Think-Pair-Share24
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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http://www.canola-council.org/canola_resources/product45.aspx
10-15% 10-15% 70-80%
Ratio of ≤2 to 1
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Polyunsaturated Fatty Acids (PUFAs) = Essential Fatty Acids (EFAs)
Omega-3Omega-6
Converted to hormonesthat slow down cell divisionand dampen inflammation
Converted to hormones that speed up cell division and trigger 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
Why a 2:1 ratio?
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Polyunsaturated Fatty Acids = Essential Fats
Omega-3Omega-6
(ALA, alpha-linolenic acid)In flax seed, nuts, canola oil
(LA, linoleic acid)Lots in corn, sunflower, soybean oil
EPA and DHAIn fatty fish
(AA)In meat, milk of grain-fed cattle
Converted to hormonesthat slow down cell divisionand dampen inflammation
Converted to hormones that speed up cell divisionand trigger inflammation
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The Yin & Yang of Inflammation
The “GOOD”: Upon injury/infection, pro-inflammatory prostaglandins “call” white blood cells to engulf & destroy injured
body cells & invaders.
The “BAD”: Overproduction of pro-inflammatory messengers causes white
blood cells to attack uninjured body cells.
http://taoism.about.com/od/visualsymbols/ig/Taoist-Symbols/Yin-Yang-Symbol.--jj.htm
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PREVENT
Healthful diet
PROMOTE
Modern western diet
High saturated fat
High omega-6:3 fatty acid ratio
Low saturated fat
Balanced omega-6:3 fatty acid
ratio
Chronic
disease
and
disorders
Impact of dietary fats on human health
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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)
SharkSwordfishKing mackerelTilefish
And alsoBluefin tunaChilean sea bassRockfishGrouperBluefish
Just FYI: Real World Advice
http://www.montereybayaquarium.org/cr/cr_seafoodwatch/download.aspx31
Which is correct?A) omega-3 fatty acids are good and omega-6 fatty acids
are badB) omega-6 fatty acids have no positive effectsA) both omega-3 fatty acids and omega-6 fatty acids
have vital roles in the human bodyD) the ratio of omega-6 to omega-3 fatty acids is not
important for human healthE) B, C, and D are all correct
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5 minute break
blog.famasalescoffee.com
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Three types of lipids:
FatsPhospholipidsSteroids
Phospholipid = phosphate + glycerol + 2 fatty acid chains
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How is a phospholipid constructed?
Fig. 5.1335
How is a phospholipid constructed?
Fig. 5.1336
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.
A. B.
C. D.
H20
H20
H20
H20
H20H20
H20
H20
hydrophilic (water-loving) polar head group
hydrophobic (water-fearing) non-polar tails
Think-Pair-Share37
Interactions of phospholipid molecules with waterThe basis of phospholipid bilayers
Hydrophilichead
Hydrophobictail WATER
WATER
Fig. 5.1438
Hydrophilichead
Hydrophobictail WATER
WATER
Fig. 5.14
Structure-function relationship: Phospholipids are key to the existence of biological cells
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Fat
Fig. 5.11
Phospholipid
Fig. 5.13
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(Three types of lipids:)
FatsPhospholipidsSteroids
Steroids = 4 carbon-hydrogen rings
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http://www.uv.es/EBRIT/macro/macro_5009_2_284.html
http://www.sciencephoto.com/media/97627/enlarge
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Steroids: What are they?
pictureschat.com; ellies-whole-grains.com; medicalinsider.com; genesistraining.org.uk
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Testosterone
Estradiol(an estrogen)
Fig. 4.9
See pages 977 & 993-994 in textbook for more information
Sex hormones are steroids.
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Cholesterol
Fig. 5.15
Made from saturated dietary fat
• Stabilizes biological membranes in animals (will be visited later)• Has a role in heart disease (will be visited later)
• Is an important precursor for other steroids45
Fig. 5.15
Precursor in synthesis of:Sex hormones, stress hormones, Vitamin D
Roles of cholesterol
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http://www.neurosci.pharm.utoledo.edu/MBC3320/steroid_hormones.htm
Synthesis of steroid stress hormones (corticosteroids) from cholesterol
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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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Fig. 5.15
Precursor in synthesis of:Sex hormones, stress hormones, Vitamin D
Roles of cholesterol
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Vitamin D2http://en.wikipedia.org/wiki/Vitamin_D
+ UV
Cholesterol
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Which lipid is most hydrophilic?
“Water and oil don’t mix!”
Fats
Fig. 5.11
Phospholipids
Steroids
Fig. 5.15
Fig. 5.13
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Fats
Fig. 5.11
Phospholipids
Steroids
Fig. 5.15
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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