CH 5: The Lipids

1
CH 5 The Lipids
2
Introduction to Lipids

• Lipids water insoluble component of cells
• Called hydrophobic
• Made of the elements
• Carbon
• Hydrogen
• Oxygen
• Phosphorus (in phospholipids only)

3
Introduction to Lipids

• Classes of lipids
• Triglycerides (TG) and fatty acids (FA)
• TG are the fats we eat
• 9 kcal/gram
• Phospholipids
• Also 9 kcal/gram
• Sterols
• Not caloric

4
Intake

• Recommended levels of intake
• 20-35 daily kcal from fats (TG)
• Maximum 10 from saturated fats
• Maximum 300 mg cholesterol per day
• No or lower cholesterol intake is fine/good

5
Triglycerides

• TG chemical nature
• 3 carbon backbone (called glycerol) with 3 fatty
  acids (FA) attached
• Nature of the attached FA determines the
  properties of the TG

6
Fatty Acids

• Fatty Acids - structure
• Long hydrocarbon chains
• Most are 4-24 carbons long
• Always an even number of carbons
• Carbon chains differ in
• Length
• Points of unsaturation

7
Fatty Acids

• Saturated Fatty Acids
• All carbon to carbon single bonds
• Chain is saturated with hydrogens
• Chain is relatively straight

8
Fatty Acids

• Unsaturated Fatty Acids
• At least one C to C double bond present
• Text calls this a point of unsaturation
• Double bonds kink/bend the chain

9
Fatty Acids

• Monousaturated FA
• One C to C double bond
• Polyunsaturated
• More than one C to C double bond

10
Fatty Acids
11
TG

• Back to TG
• Glycerol with 3 FA attached
• FA may differ
• Nature of FA impacts properties of the TG

12
Triglyceride
13
TG

• TG with primarily saturated FA
• Solid
• Primarily from animal sources
• Plant sources palm and coconut oil

14
TG

• TG with primarily saturated FA
• More stable than TG w/ unsaturated FA
• Store better
• Associated w/ health risks

15
TG

• TG with primarily unsaturated FA
• Liquids (oils)
• Primarily from plant sources
• Plant TG are primarily unsatd FA
• FYI - Animal TG are a mixture of satd and
  unsatd FA

16
TG

• TG with primarily unsaturated FA
• Double bonds are reactive
• Therefore plant oils react with oxygen and go
  rancid easily

17
TG

• Food Sources Saturated Fats
• Butter, cream, milk, cheese
• Red meat
• Chicken and fish are a mixture of satd and
  unsatd fats

18
TG

• Sources of Unsaturated Fats
• Monounsaturated
• Olive oil, canola oil, peanut oil
• Polyunsaturated
• Corn oil, soybean oil, sunflower oil..

19
Fatty Acids

• Essential Fatty Acids
• Omega-3 FA gt double bond 3 C from the end
• May lower cholesterol and risk of heart disease,
  hypertension, ?cancer, ?arthritis
• Good food sources fish, soy, nuts, many oils

20
Triglyceride
21
Fatty Acids

• Essential Fatty Acids
• Omega-6 FA gt double bond 6 C from the end
• Food sources are vegetable oils and poultry

22
Hydrogenation

• Hydrogenation reaction
• Adds hydrogens to double bonds
• Removes kinks from FA chains

23
Hydrogenation

• Partially hydrogenated TG
• Some of double bonds saturated (made single
  bonds)
• As a result oils become ___________

24
Hydrogenation

• Partially hydrogenated TG
• Often the remaining double bonds converted from
  cis to trans form
• Cis form is the naturally occurring form
• Trans FA are associated with health risks

25
Hydrogenation

• Fully hydrogenated TG
• All double bonds are saturated
• As a result oils become solids (stick margarine)

26
Hydrogenation

• Fully hydrogenated TG
• Converts an unsaturated oil to a saturated fat
• Fully hydrogenated fats have the same health
  issues as natural sources of satd fats

27
Phospholipids

• Function structural component of all cell
  membranes
• Structure
• Glycerol backbone (3 carbon) with 2 fatty acids
  attached and one phosphate group
• Attached to phosphate group is some other group
  (see pg 136)

28
Phospholipids

• 9 kcal/gram
• Best known phospholipid is lecithin
• Supplements are NOT needed
• Can cause GI distress, loss of appetite
• Liver makes phospholipids for the body

29
Phospholipids

• Food sources
• Eggs (yolk only)
• Liver
• Soybean
• Wheat germ
• Peanuts

30
Sterols

• Structure 4 linked carbon rings with side
  chains
• Examples of sterols (we make in body)
• Cholesterol
• Vitamin D
• Bile salts
• Sex hormones

31
Digestion of Lipids

• Goal is to digest TG to
• Glycerol, fatty acids, and monoglycerides

32
Digestion of Lipids

• Small amount of chemical digestion occurs in
  mouth and stomach
• Infants have an enzyme that begins digestion of
  TG found in milk in mouth
• Adults make a small amount of gastric lipase
• Begins digestion of TG in ______

33
Digestion of Lipids

• Small Intestine
• Bile emulsifies fats (physical digestion)
• Pancreatic and SI lipases remove FA from TG
• Digestion produces

34
Absorption

• Glycerol and short/medium chain FA
• Absorbed into the capillaries
• Go directly to the liver

35
Absorption

• Long chain FA and monoglycerides
• Form micelles
• Micelles absorbed into SI cells
• In SI cells TG are remade!

36
Absorption

• Long chain FA and monoglycerides
• IN the cells of the SI, newly made TG and
  cholesterol are packaged with transport proteins
  to make a chylomicron
• Chylomicrons are absorbed into lacteals

37
Transport

• Chylomicrons lipoproteins
• Travel through lymph and enter blood in chest
• Travel through the heart and then body
• Deliver some fats and cholesterol to cells
• Chylomicron remnants are then delivered to the
  liver

38
Transport

• In the liver
• Liver breaks down remaining TG and remakes them!
  
• Liver also makes cholesterol and other TG
• These TG and cholesterol are packaged with
  proteins to make VLDL
• Very low density lipoproteins

39
Transport

• VLDL enters blood
• VLDL delivers cholesterol and TG to needy cells
• Density goes up as the fats leave the transport
  protein

40
Transport

• VLDL becomes LDL
• Low density lipoprotein
• LDL is high in cholesterol
• LDL circulates in blood looking for cells that
  need cholesterol
• Also picks up cholesterol from other lipoproteins

41
Transport

• LDL
• Bad cholesterol
• Contributes to plaques when cholesterol falls
  off the LDL and is deposited on artery walls
• Plaques narrow arteries
• Raises blood pressure
• Increases risk of blood clots and heart attacks

42
Transport

• HDL
• High density lipoprotein
• HDL transports cholesterol and other lipids back
  to liver for disposal
• Can pick up cholesterol from plaques
• Good cholesterol

43
Cholesterol

• Maximum level of intake recommended
• 300 mg/day
• Make all we need, so no intake is fine
• Food Sources all animal (no plant sources)
• Egg yolk
• Dairy (unless fat removed as in skim milk)
• Meat, poultry

44
Cholesterol

• Blood levels
• Goal total cholesterol lt 200 mg/dL (know this
  one)
• Other recommendations (do not need to know)
• LDL lt 100 mg/dL
• HDL gt 60 mg/dL
• LDLHDL ratio to be less than 5 for men and less
  than 4.5 for women
• Triglycerides lt 150 mg/dL

45
Lowering Cholesterol Levels

• Reduce intake of
• Saturated fats
• Trans fatty acids
• Cholesterol
• Sugars (if sugar sensitive)
• Increase intake of
• soluble fibers (oats and legumes)
• fish

46
Lowering Cholesterol Levels

• Moderate alcohol intake
• Exercise aerobic may be best
• Lose weight
• FYI - Estrogen lowers cholesterol levels
• Therefore, cholesterol levels often go up in
  postmenopausal women.

47
Weight Loss and Cholesterol
48
Genetics MatterMale with a healthy weight and
active lifestyle, but family history of heart
disease
49
Functions of Fats in the Body

• Source of energy
• Thermal insulation
• Protect and supports organs
• Fats hold some organs in place
• Use to make all cells
• Use to make important substances
• E.g. sex hormones, bile

50
Review Fat Sources

• Saturated Fats
• Monounsaturated Fats
• Polyunsaturated Fats
• Trans Fatty Acids
• Cholesterol

51
Review Health Aspects Fats

• Saturated Fats
• Trans Fatty Acids
• Cholesterol
• Monounsaturated Fats
• Polyunsaturated Fats