1. Chap. 6: Lipids

2. Non-polar: water insoluble Energy density = Monomers:
Properties of Lipids
Non-polar: water insoluble
Energy density =
Monomers:
fatty acids & glycerol

3. LIPIDS: Classes True fats: 95 % are triglycerides Phospholipids
Fats: generic name, solid at room temp
Oils:
Phospholipids
Sterols

4. Fatty Acid Structure: omega end (methyl) alpha end (Carboxylic)
H H H H H H H H H H H H H H H H H O
H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH
H H H H H H H H H H H H H H H H H
omega end (methyl) alpha end (Carboxylic)
Hydrocarbon chain

5. Saturated Fatty Acid Structure
H H H H H H H H H H H H H H H H H O
H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH
H H H H H H H H H H H H H H H H H
omega end alpha end
Only single carbon-carbon bonds
Linear, pack tightly; solids
Red meat- highest % of SF; Chicken has lower % of Saturated fat

6. Monounsaturated Fatty Acid Structure
H H H H H H H H H H H H H H H O
H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end alpha end
One double bond
Canola oil and Olive oil high in monounsaturated FA

7. Polyunsaturated Fatty Acid Structure
H H H H H H H H H H H H H O
H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end alpha end
> 2 double bonds
Corn, soybean, sunflower, safflower oils rich in polyunsaturated FA.

8. Chain Length of Fatty Acids: Affects fluidity
Long chain Saturated FA
> 12 Carbons
Solid at room temperature
Medium chain FA (e.g coconut oil)
Carbons
Short chain FA: (e.g. dairy fats)
< 6 Carbons
Direct absorption from intestinal cell into the blood

9. Essential fatty acids: EFAs
Humans cannot synthesize double bonds within the fist 9 carbons from the methyl end (n) of any fatty acid chain
Fatty acids with double bonds in those locations must therefore come from the diet—and are considered essential
Thus, EFA are (poly)unsaturated
There are no essential saturated fats

10. Essential Fatty Acids
Omega-3 fatty acids: alpha linolenic acid (C18:3; w3)
Omega- 6 fatty acids: Linoleic acid (C18:2; w6)
Role in
Immune systems
Cardiovascular systems
Nervous systems
vision,
cell membrane,
production of eicosanoids
Omega 9 FA necessary but not essential
oleic acid (C18:1; w-9)

11. Essential Fatty Acid- Omega-3 (alpha-linolenic acid)
H H H H H H H H H H H H H H H H H O
H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H
omega end alpha end
1st double bond is located on the 3rd carbon from the omega end

12. Omega-3 Fatty Acids Family
Alpha linolenic acids
Eicosapentaenoic acid (EPA) (C20:5; w3)
Docosahexaenoic acid (DHA)(C22:6;w3)
Primarily from fish oil & also canola or soybean oil
Metabolized to form eicosanoids:
hormone-like compounds required for growth
Regulates blood pressure, childbirth, clotting, immune responses, & stomach secretions for growth
Recommend: ~2 servings fish/week
1g/d needed esp in cases of CVD

13. Essential Fatty Acid- Omega-6 (alpha-linoleic acid)
H H H H H H H H H H H H H O
H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end alpha end
1st double bond is located on the 6th carbon from the omega end

14. Omega-6 Fatty Acids Family
Linoleic acid,
Arachidonic acid ,
Dihomo-gama linoleic acid
Metabolized to form eicosanoids
In vegetable oils; need ~ 1 TBS a day
Read page 184

15. Signs and Symptoms of Essential Fatty Acids Deficiency
Flaky, itchy skin
Diarrhea
Infections
Retarded growth and wound healing
Anemia

16. Triglycerides: ester bondsH
H--C--OH
Fatty Acid
H O
H--C--O--C-- O H
Fatty Acid +
Fatty Acid
Fatty Acid
esterification/reesterification
deesterification
Deesterification can form di and monoglycerides
This is the breaking of FA from glycerol, reesterfication is the reverse
Free FA, monoglyceride and glycerol can freely cross the cell membrane

17. Functions of Triglycerides
Provide energy: for light activity, rest & sleep
Efficient storage of energy:
9kcal/kg; adipose cells can increase in size x50 to accommodate more fat pg 166
More cells can be synthesised, body efficient in storing fats
Insulation
Loss of subcutaneous fats results in Lanugo
Downy hair that appears after a person has lost much fat through semi-starvation
Seen in people with anorexia nervosa
Protection
Transport fat-soluble vitamins
Satiety
Flavor and mouth feel

18. Functions of Phospholipids
Non-essential
Cell membrane
Eicosanoid synthesis
Lecithin emulsifies fat to micelles (small fat droplets)
Plenty in peanuts, egg yolk, liver, soybean
Bile acids contains lecithins, acids,cholesterol

19. Sterols
Waxy substance, no glycerol or FA backbone; a multi-ringed structure
Non essential; made from acetyl CoA
Cholesterol is a sterol only in animal products
Essential component of cell membrane
Forms important hormones
Estrogen, testosterone, vitamin D
Precursor of bile acids
See table 6.2

20. Digestion of Fat in the Stomach
Little digestion in stomach aided by
Gastric lipase
Short & medium FA chain triglycerides
Long FA chain unaffected

21. Digestion of Fat in the Small Intestine (SI)
SI is the primary site of fat digestion
Cholecystokinin (CCK): hormone in duodenum
causes the gallbladder to release bile and the
the pancreas to secrete pancreatic lipase
Pancreatic colipase- coenzyme
Products of fat digestion are
Monoglycerides, glycerol & fatty acids

22. Absorption
FA, Glycerol and monoglycerides form little micelles /spherical structures
Absorption is by enterocyte thru the villi of SI
Short chain FA ---hepatic portal vein to liver
95 % absorption rate

23. Absorption Long Chain FA: reformed into triglycerides
Packaged into lipoproteins
Large lipid droplet surrouned by protein, triglyceride, phospholipid and cholesterol
Chylomicrons: LPPs produced by small intestine

25. Absorption Lipoproteins In blood vessels
Lymphatic system via lacteals & then circulatory system
In blood vessels
Lipoprotein Lipase breaks triglycerides in chylomicrons
FA are absorbed by cells (muscle or adipose)
Takes 2-10 hrs to clear the chylomicrons from the blood circulatory system

26. From Last week Chylomicrons consist of:
A core made of lipids (triglycerides and cholesterol bound to fatty acids)
A shell made of cholesterol, protein, phospholipids and apolipoproteins (apolipoproteins aid in transport of chylomicrons to target cells)
Chylomicrons transport diet-derived lipids (mostly triglycerides) from the small intestine to other body locations.
The chylomicron gets smaller and smaller as it hands off the triglycerides to body cells.
After ~ 2-10 hours following absorption, only protein remnants and small amounts of lipid remain.
The liver picks up these remnants, removing them from the circulation.

27. Fate of fats and cholesterol made in the liver
Liver synthesizes fat and cholesterol using FA, glycerol and triglycerides in vessels
Processes them into
Very Low Density Lipoprotein (VLDL)
Transport cholesterol, & lipid produced by the liver
VLDL goes into the blood stream from the liver
Are broken down by Lipoprotein Lipase, release FA, glycerol
FA taken up by body cells
As the triglycerides are removed, the lipoprotein becomes heavier, or more dense
The lipoprotein is now converted into a low-density lipoprotein, or LDL, containing mainly cholesterol.

28. Uptake of LDL Receptor Pathway for cholesterol
A process by which LDL is bound by cell receptors and incorporated into cells where cholesterol is broken down or used for building cells
when diet is low in saturated fat and cholesterol
Removes LDL from circulation

29. Uptake of LDL Scavenger pathway for cholesterol
A process by which LDL is taken by scavenger cells embedded in the endothelium of blood vessels
LDL is oxidized, forms a plaque,
a thick, hard deposit that can clog those arteries
Atherosclerosis
Antioxidants (Vit C, Vit E, carotenoids) found in fruits and vegetables reduces risk of coronary heart disease
Prevent oxidation of LDLs

30. High Density Lipoprotein (HDL)
Synthesized by liver and intestine
High proportion of protein, thus dense
Picks up cholesterol from dying cells and other sources
Transfers cholesterol to other lipoprotein for transport to the liver for excretion
HDL can also transfer directly back to the liver

31. Benefits of (a high) HDL (level)
Remove cholesterol from the blood stream
HDL may block oxidation of LDL
Reduce risk of heart disease
High HDL in blood = good
Low HDL in blood = problems
Little cholesterol to the liver for excretion
Common in men

32. Hydrogenation of Fatty Acids
Process used to solidify an oil
Forms trans fatty acid with hydrogen on opposite sides of the double bond.
Causes backbone to remain straight and allows tighter packing just like saturated FA
CIS configuration common in mono & polyunsaturated fatty acid
See figure 6.15

33. Health Dangers of Excessive Trans Fatty Acid
Raises LDL levels
Lowers HDL
Increases risk for heart disease
Current intake is~3% of total kcals (10g/d)
FDA requires trans fat content on food labels
Examples of spreads with low or no trans fats:
Smart beat
Promise
Fleischmann

34. Minimize Intake of Trans Fatty Acid
Limit use of hydrogenated fats
Limit deep-fried foods
Limit high fat baked goods
Limit use of non-dairy creamers
Restaurant foods high in trans-fatty acids and saturated FA
Read page 222

35. Rancidity Decomposed oils emit an odor, taste, sour taste due to
Breakdown of the C=C double bonds by ultraviolet rays, and O2
Yields unpleasant odor, flavor, and sickness when consumed
Limits shelf life
Food more prone
Food with high PUFA
Deep fried foods
Powdered eggs
Powdered milk, cake mixes,
Fat in fish

36. Prevention of Rancidity
Hydrogenation
Addition of vitamin E
Addition of Butylated hydroxyanisol (BHA) and Butylated hydroxytolune (BHT)
Common synthetic antioxidants

37. Added to salad dressing and cake mixes to vegetable oil in water
Emulsifiers
Monoglycerides
Diglycerides
Polysorbate 60
Eggs added to cake batter
Added to salad dressing and cake mixes to vegetable oil in water

38. American Heart Association’s Recommendations
AI set by American Heart Association
20%-30% of total energy intake (TEI) from all fats
47-70g/d
7% -10% of TEI from saturated and trans fat
mg cholesterol /day
Limit intake of trans fatty acid
Low fat is not recommended for children under 2 years of age
See also Tables 6.6 & 6.7
Essential fatty acids intake~ 5 % of total energy intake
Linoleic acid (omega-6) 17g/d for men and 12 g/d for women
Alpha linolenic acid (Omega –3), 16 (men); 1.1 (women)

39. Fats in Foods Fat rich foods (~100% of energy as fat)
Salad oils
Butter
Margarine: 80%
Mayonnaise
Foods with 80% energy as fat
Walnuts
Bologna
Avocadoes
Bacon
Peanut – butter: 75 %
Cheddar cheese: 75 %

40. Fats in Foods Foods with 35% of energy as fat Eggs Pumpkin pie
Cup cakes
Lean cuts
Meat-top round

41. Animal Fats 40-60% of fat is saturated
Saturated fats contributes to high LDL
Lauric acid: 12 C
Myristic acid: C
Palmitic: 16
Dairy foods also high in fats that raise LDL levels in blood, rich in myristic acid

42. Plant Oils Mostly unsaturated FA: 73-94% of total
Canola, olive, & peanut oils:
50-80% monounsaturated FA
Corn, cottonseed, sunflower, soybean, safflower:
mostly poly-unsaturated FA
50-80% of total fat
Supply omega -3 and omega- 6 FA

43. FAT-Free = “all you can eat”
Sales of reduced fat food were projected to rise to 32 billion by year 2001
When fat is removed, sugar is added in its place
Fat free = Calorie free
Calorie content is still similar to full-fat version
Eat reduced fat foods in moderation

44. Fat Substitutes Z-trim Starch derivative
Made from hulls of soybean, peas & rice or bran (corn or wheat)
Absorbs large amounts of water to form a gelatin-like product
Used in a variety of foods
Creates mouth-feel
Contains less calorie than fat but does not remove all calories
Not used for frying

45. Fat Substitutes Dairy-Lo Used in milk and other dairy products
Contains eggs, milk protein treated with microscopic protein globules
Mouth feel of fat, without the fat
1-2 kcal/gm due to pn & water
High water content

46. Fat Substitutes Olestra (Olean) Engineered fat
Fatty acids linked to sucrose
Not digested by human or bacterial enzymes
Yields no calories
Can be used in frying or can replace all fat in salad dressing and cakes
Problem: bind fat soluble vitamins and carotenoids in a meal
Over-consumption may cause cramping and loose stool
May bind to carotenoids in the meal