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Chapter 5:LIPIDS

NFS284: Basic Human Nutrition

Lecture 1:- Types of Lipids- Chemical structure of Lipids- Food sources of fatty acids- Digestion and absorption- Metabolism of dietary fat

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Case StudySam is 20yr University student

His grandfather died of a heart attack at age 50.He is 10kg overweight; blood cholesterol 5.4mmol/L.Eats red meat, whole milk, ice cream, & 1-2 F&V daily.Exercise: frisbee on Tues and weights on Fri.

e s concerne a out r s or . atshould he do? Advice from friends:Vegetarian girlfriend: eliminate meatLab partner: cut out all fatSister: Mediterranean diet (pasta and olive oil)Roommate: eat more fishMother: stop using margarine due to the trans fat it

containsCopyright 2010, John Wiley & Sons, Inc.

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What Are Lipids?A diverse class of molecules that do notdissolve in waterThree types of lipids are found in foods:

PhospholipidsSterols

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TriglyceridesMajor form of lipid in food and in the body.

Consist of:3 fatty acids : long chains of carbon atomssurrounded by hydrogen atoms

One glycerol molecule: a 3-carbonalcohol that is the backbone of atriglyceride

Copyright 2012, John Wiley & Sons Canada, Ltd.

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Triglycerides


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TriglyceridesFatty acids can differ in

Length of their carbon chainShort-, medium-, or long-chain

Level of saturationSaturation refers to how many hydrogen atoms surroundeach carbon

Shape

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Triglycerides Chain LengthThe shorter the chain

The more liquid fats are at room temperatureThe more soluble they are in water

h r - h in w r h n r n m Acetic Acid (CH 3-COOH) - vinegar

Medium-chain: 6-12 carbonsTropical oils, milk

Long-chain14 or more carbons (most common fats)

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Milk: Chain length of SaturatedFatty Acids

4:0-6:0

8:0-12:0

14:0

16:0

18:0

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Saturated fatty acids have hydrogen atoms aroundevery carbon in the chain.

Monounsaturated fatt acids lack hydrogen atoms

Triglycerides: Degree of Saturation

C16:0

at one carbon; theyhave one double bond.

Polyunsaturated fatty acidshave > 1 double bonds.

C18:1

C18:2

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Some important fatty acidsC16:0 Palmitic acidC18:0 Stearic AcidC18:1 Oleic Acid

C18:2 6 Linoleic acidC18:3 3 Alpha-linolenic acid (ALA)C20:4 6 Arachadonic acidC20:5 3 Eicosapentaenoic acid (EPA)C22:6 3 Docosahexaenoic acid (DHA)

know fatty acids marked with arrows

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Triglycerides - ShapeThe shape of a triglyceride is determined bythe saturation of the carbon chains and bythe type of double bond.

The hydrogen atoms at the unsaturatedregion can be arranged in different positions:

Cis same side of the carbon chain

Trans opposite sides of the chain

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Fatty Acids: ShapeThe more unsaturated, the more liquid at room temperature.


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Turn this .. into this?

Hydrogenation!

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Hydrogenation : The addition of hydrogenatoms to unsaturated fatty acids.

Coverts liquid fats (oils) into a more solid

Used to create margarine from plant oilOften creates trans fatty acids

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Oleic Acid

Creation of Trans Fatty Acidsby Hydrogenation

Elaidic AcidStearic Acid

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Essential Fatty AcidsEssential fatty acids

Two fatty acids cannot be synthesized in the bodyand must be obtained in the dietAlpha-linolenic acid (omega-3 fatty acid): C18:3 3

oo ources: ax, s an s o sLinoleic acid (omega-6 fatty acid) C18:2 6Found in vegetable and nut oils

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HO

O

1

9 12 18

169Linoleic Acid

HO

O

1

9 12 1815

169 3

Alpha-Linolenic Acidomega end

omega name based onposition of first doublebond

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Fatty Acids in Food

MUFA

-3


SFA

coconut oil is stillliquid due toshorter chain

saturated fats -meats, tropicaloils, usuallycaused by highcarbohydrateintake

be able to compare relative amounts of fats in each source

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Omega-3 and Omega-6 Fatty Acids


C18 conversionrequired, lowefficiency

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Food Sources of Trans Fatty Acids

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PhospholipidsAre composed of

Glycerol backbone2 fatty acidsPhosphate

Polar head-groupAmphipathic

Both hydrophilic and hydrophobic

Are emulsifiersForm a lipid bi-layer

Not required in our dietCopyright 2012, John Wiley & Sons Canada, Ltd.

Phosphatidylcholine(lecithin)

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SterolsLipids containing multiple rings of carbon

atoms.Are essential components of cell membranes andmany hormones

Are manufactured in our bodies and therefore arenot essential components of our diet

Dietary SterolsCholesterol (animal products)Plant sterols

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Sterols

Vitamin D 3

You are NOTrequired to knowthe structures.

made from acetate

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Cholic Acid Progesterone

Testosterone Estradiol

You are NOT required to know the structures.

bile acid

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Fat digestion

MouthLingual lipaseEnzyme that digests

Copyright 2010, John Wiley & Sons, Inc.

But, very little fat isdigested

possibly for taste, but digestionaspect is insignificant

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Fat digestion

LiverProduces bileStored in gall bladder


intestineEmulsifies fat

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Role of Bile: Emulsification

Micelles

brings fat into hydrophilic layer, increasing surface area fordigestion

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Fat digestion

LiverProduces bileStored in gall bladder


intestineEmulsifies fat

Pancreas

Secretes lipaseCleaves triglyceride intofatty acids andmonoglycerides

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Fat digestion


monoglyceride and fa -long and insoluble,therefore carried intoGolgi and er, formedinto solublechylomicrons releasedinto lacteals. shorterfas may be directlydigested

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Portal Vein vsLymphatics

fat usually doesn't go to liver (fatty liver=bad), so it ends up in the lymphcirculation

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LipoproteinsLipoproteins are particles which transport

lipids and fat-soluble vitamins in the blood.Lipoproteins contain fats, sterols,

.Lipoproteins are made in the small intestineand liver.


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Lipoproteins


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Types of LipoproteinsChylomicrons

VLDL (very low density lipoprotein)IDL (intermediate density lipoprotein)

ow ens y popro e nHDL (high density lipoprotein)

know these

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Transport of Dietary Fat

Chylomicron


remnant

Adipose tissue (90%)Muscle (10%)

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Lipaemic Plasma

Normal

LipaemicFasting Postprandial

turbulent,increase offats

lipoproteinlipasedeficiency,extreme fat

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Next LecturesLipids 2

AlcoholEndogenous fat metabolismFood sources of fatRole of fat in the body

Lipids 3Cardiovascular diseaseDietary fat and health

REQUIREDREADING:

- Section 5.6 in textbook - Critical Thinking:Lowering risk of heart disease

- Section 5.7 in textbook Label LiteracyChoosing lean meat

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Copyright

Copyright 2012 John Wiley & Sons Canada, Ltd.

All rights reserved. Reproduction or translation of this work beyond thatpermitted by Access Copyright (The Canadian Copyright LicensingAgency) is unlawful. Requests for further information should be

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Ltd. The purchaser may make back-up copies for his or her own useonly and not for distribution or resale. The author and the publisherassume no responsibility for errors, omissions, or damages caused bythe use of these programs or from the use of the information containedherein.

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NFS284 - 6 - Lipids I