The Lipids: Triglycerides, Phospholipids and Sterols

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The Lipids Triglycerides, Phospholipids and
Sterols
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Lipids Objectives

• 1. Understand the chemical composition and
  differences between fats
• 2. Explain the structural and functional
  processes of triglycerides, phospholipids, and
  sterols
• 3. Describe the process of fat digestion and
  absorption
• 4. Discuss the different types of lipoproteins
  in the body
• 5. Clarify the recommended intakes of fat and
  essential fatty acid requirements to meet daily
  nutritive needs
• 6. Describe the health-risk factors with over
  consumption of lipids in the diet

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Triacylglycerol Triglycerides
R-COO-CH2 R-COO-CH R-COO-CH2

• Triglycerides found in seeds and
• animal adipose.
• Diglycerides found in plant leaves,
• one fatty acid is replaced by sugar
• (galactose).

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Most Common Fatty Acids in Di- and Triglycerides
Fatty acid CarbonDouble bonds Double bonds
Myristic 140
Palmitic 160
Palmitoleic 161 Cis-9
Stearic 180
Oleic 181 Cis-9
Linoleic 182 Cis-9,12
Linolenic 183 Cis-9,12,15
Arachidonic 204 Cis-5,8,11,14
Eicosapentaenoic 205 Cis-5,8,11,14,17
Docosahexaenoic 226 Cis-4,7,10,13,16,19
CH3(CH2)nCOOH
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Triglyceride Containing Linoleic Acid Omega-6
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Linolenic Acid Omega-3
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Fatty Acid Isomers
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Fatty Acids

• The Length of the Carbon Chain
• long-chain, medium-chain, short-chain
• The Degree of Unsaturation
• saturated, unsaturated, monounsaturated,
  polyunsaturated
• The Location of Double Bonds
• omega-3 fatty acid, omega-6 fatty acid

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Lipid Content of Feeds
Forages Fat content is low 1 to 4 of dry
matter High proportion of linolenic acid
(183) Diglycerides in fats of leaves Grains Fat
content variable 4 to 20 of dry matter High
proportion of linoleic acid (182) Triglycerides
in oils of seeds
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The Length of the Carbon Chain
Short-chain Fatty Acid (less than 6
carbons)
Medium-chain Fatty Acid (6-10 carbons)
Long-chain Fatty Acid (12 or more carbons)
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Fatty Acids are Key Building Blocks

• Saturated Fatty Acid
• All single bonds between carbons

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Monounsaturated Fatty Acid(MUFA)
One carbon-carbon double bond
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Polyunsaturated Fatty Acid(PUFA)
More than one carbon-carbon double bond
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Location of Double Bonds

• PUFA are identified by position of the double
  bond nearest the methyl end (CH3) of the carbon
  chain this is described as a omega number
• If PUFA has first double bond 3 carbons away from
  the methyl endomega 3 FA
• 6 carbons from methyl endomega 6 FA

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Degree of Unsaturation

• Firmness
• saturated vs. unsaturated
• Stability
• oxidation, antioxidants
• Hydrogenation
• advantages, disadvantages
• Trans-Fatty Acids
• from hydrogenation

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Hydrogenation
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Cis-fatty acid Hs on same side of the double
bond fold into a
U-like formation naturally occurring Trans-fatty
acid Hs on opposite side of double bond
more linear occur
in partially hydrogenated foods
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Essential Fatty Acids (EFA)

• Omega-3
• Eicosopentaenoic acid (EPA)
• Docosahexaenoic acid (DHA)
• Alpha-linolenic acid (ALA)
• flaxseed--most, canola (rapeseed), soybean,
  walnut, wheat germ
• body can make some EPA and DHA from ALA
• Omega-6
• corn, safflower, cottonseed, sesame, sunflower
• Linoleic acid

FISH
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Omega-3
Omega-6
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Omega-3 Fatty Acids

• Associated with
• anti-inflammatory, antithrombotic,
  antiarrhythmic, hypolipidemic, vasodilatory
  properties
• Inflammatory conditions
• Ulcerative colitis, Crohns
• Cardiovascular disease
• Type 2 diabetes Mental function
• Renal disease Growth and
  development

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Essential Fatty Acid Deficiency

• Classical symptoms include
• growth retardation, reproductive failure, skin
  lesions, kidney and liver disorders, subtle
  neurological and visual problems
• People with chronic intestinal diseases
• Depression--omega-3
• ?inadequate intake alters brain activity or
  depression alters fatty acid metabolism?
• Attention Deficit Hyperactivity Disorder
• lower levels of omega-3--more behavioral problems

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Eicosanoids made from EFA --derivatives of
20-carbon fatty acids --affect cells where they
are made --have different effects in different
cells --cause muscles to contract and muscles to
relax --help regulate blood pressure, blood clot
formation, blood lipids, and immune
response --participate in immune response to
injury and infection, producing fever,
inflammation, and pain --includeprostaglandins,
thromboxanes, leukotrienes
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Triglycerides

• Structure
• Glycerol 3 fatty acids
• Functions
• Energy source
• 9 kcals per gram
• Form of stored energy in adipose tissue
• Insulation and protection
• Carrier of fat-soluble vitamins
• Sensory properties in food

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Triglycerides lipids composed of three fatty
acids attached to a glycerol
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Triglycerides

• Food sources
• fats and oils
• butter, margarine, meat, baked goods, snack
  foods, salad dressings, dairy products, nuts,
  seeds
• Sources of omega-3 fatty acids
• Soybean, canola, walnut, flaxseed oils
• Salmon, tuna, mackerel
• Sources of omega-6 fatty acids
• Vegetable oils

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Fatty Acids in Common Food Fats
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Phospholipids

• Structure
• Glycerol 2 fatty acids phosphate group
• Functions
• Component of cell membranes
• Lipid transport as part of lipoproteins
• Emulsifiers
• Phosphatidylcholine
• Food sources
• Egg yolks, liver, soybeans, peanuts

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Cell membranes are phospholipid bilayers
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Sterols Cholesterol

• Functions
• Component of cell membranes
• Precursor to other substances
• Sterol hormones
• Vitamin D
• Bile acids
• Synthesis
• Made mainly in the liver
• Food sources
• Found only in animal foods