Lecture 3: Lipids: Fats, Phospholipids, Steroids 1.

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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