Chap. 5: Lipids. Properties of Lipids Do not readily dissolve in water Fats are solid at room temperature Oils are liquid at room temperature Triglycerides.

Chap. 5: Lipids

Properties of Lipids

Do not readily dissolve in water

Fats are solid at room temperature

Oils are liquid at room temperature

Triglycerides are the main form of lipids in food and body (storage)

Energy dense (9 kcal /gm)

Fatty Acids

Basic Form of Fats

Form together to make use for the body and for foodSaturatedUnsaturatedPolyunsaturated

Fatty Acid Structure (Fig. 5-1-A)

omega end alpha end

degree of saturation

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

Saturated Fatty Acid Structure (Fig. 5-1-A)

omega end alpha end

degree of saturation: single carbon bond

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

Monounsaturated Fatty Acid Structure (Fig. 5-1-B)

omega end alpha end

One double bond

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

Polyunsaturated Fatty Acid Structure (Fig. 5-1-C)

omega end alpha end

> 2 double bonds

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

Essential Fatty Acids

Body can only make double bonds after the 9th carbon from the omega end

Primarily need Omega-3 and Omega-6

Essential Fatty Acid- Omega-3 (alpha-linolenic acid)

omega end alpha end

1st double bond is located on the 3rd carbon from the omega end

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-3 Fatty Acid

Primarily from fish oil

Also found in canola or soybean oil

Recommend intake of ~2 servings of fish per week

(Omega-3)Alpha-linolenic acid

decrease blood clotting reduces heart attackexcess may cause hemorrhagic stroke large amounts may decrease inflammation

pain with rheumatoid arthritis

Essential Fatty Acid- Omega-6 (alpha-linoleic acid)

omega end alpha end

1st double bond is located on the 6th carbon from the omega end

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-6 Fatty Acid

Found in vegetable oils

Only need ~ 1 tablespoon a day

Linoleic acid (Omega-6)Arachidonic acid

increase blood cot increase inflammatory responses

Fats in the body/food

TriglyceridesMain form of fats in the body and in food

PhosolipidsManufactured by the liver (not essential)

SterolsManufactured by the liver and in food

Differ based upon structure & function

Triglycerides

Structure:3 fatty acids connected to a glycerol

backbone

Function:Main form of fats in food and bodyTaken up my muscles for energyTaken up by adipose tissue for storage

Triglycerides

(Ester bond)

Glycerol + 3 FA’s Triglyceride +

3 H20

H

H--C--OH

H--C--OH

H--C--OH

H

O

HO-C-R

O

HO-C-R

O

HO-C-R

+

H O

H--C--O--C--

O

H--C--O--C--

O

H--C--O--C--

H

R + H2O

R + H20

R + H20

Phospholipid

Structure:Built on a glycerol backboneHas at least one fatty acid replaced with

phosphorus compound

Function: EMULSIFICATIONNeeded for transport of triglycerides and

sterols Needed for breakdown of triglycerides

inside the cellPart of the cell membrane

Functions of Phospholipids cont.

Emulsifier Bile acidsLecithins Improves food products

Emulsifier

Hydrophilic end (attracts water)

Hydrophobic end (attracts lipid)

Emulsification

Sterol--Cholesterol

Structure:A multi-ringed structureDo not have a glycerol backboneWaxy substance

Function:Needed for cell structureNeeded for bile and hormone production

Digestion

Digestion of Fat in the Stomach

Gastric lipase works only on triglycerides containing short & medium chain fatty acid

Minimal digestion in the stomach

Digestion of Fat in the Small Intestine

Primary site of fat digestionCCK stimulates pancreas to release pancreatic lipaseBile acid emulsifies digested fatFat is broken down to monoglycerides and fatty acids

Absorption of Fat

Short and medium chain (<12 C) fatty acids are water solubleEnters the portal system

Long chain fatty acids reforms into TGEnters the lymphatic system

Carrying Fat in the Bloodstream

Water (blood) and oil (fat) are incompatible

Unique system of fat

transportation is needed Fat

Transportation of Digested Fat

Re-formed triglycerides are packaged into a lipoprotein called chylomicrons

Enters Lymphatic System

Enzymes in the chylomicrons break down triglycerides

Fatty acids are absorbed by cells (i.e. muscles or adipose)

Lipoproteins

Transportation of Synthesized Fat

LIVER: takes up lipids from bloodManufactures fats (lipids) and cholesterolSynthesizes new lipoproteins and releases

them into the blood stream

LIPOPROTEINS produced by the liver

VLDL becomes more dense as it releases lipid to cells;

turns into LDL carries and releases fat

LDL carries and releases cholesterol and protein

HDL Cleans up loose cholesterol in the blood High proportion of protein

Benefits of HDL

Remove cholesterol from the blood stream

HDL may block oxidation of LDL

Reduce risk of heart disease

Pre-menopausal women have higher HDL

Good vs Bad Cholesterol

CVD increases with low HDL

If LDL not cleared from bloodstream, WBC’s take it to the arteries

Eventual build up of cholesterol in BV

Leads to CVD

Functions of Lipids (a recap)

Provide energy (muscles)

Efficient storage of energy (in adipose)

Insulation/Protection

Transport fat-soluble vitamins

Satiety

Flavor and mouth feel

Lipids in Foods

Hidden Fat

Look on the Nutrition Facts

Look on the lists of ingredients

Control portion size

Reduce-Fat Foods

Total energy is about the same

Sugar is commonly added in place of fat

Hydrogenation of Fatty Acids

Process used to solidify an oilAddition of H to C=C double bondsIncreases shelf lifeDecreases rancidityFormation of trans fatty acid (similar to shape of saturated fatty acid)

Health Dangers of Excessive Trans Fatty Acid

Raises LDL

Lowers HDL

Increases risk for heart disease

Current intake is~3% of total kcals

Soon to be on food labels

Where do we get Trans Fatty Acids?

hydrogenated fats

deep-fried foods

baked goods

non-dairy creamers

Rancidity

Decomposed oils

Breakdown of the C=C double bonds by ultraviolet rays, &/or O2

Yields unpleasant odor and flavor

PUFA more susceptible

Limits shelf life

RecommendationEssential fatty acids:2 servings of fatty fish/wk2-4 Tbls. of plant oil

~ 20-35% of total caloric intakeCurrent diet supplies ~33% of total kcal

from fatmuch from animal, whole milk, pastries,

cheese, margarine, and mayo

The American Heart Association

For high risk individuals

<20-30% of total kcal from fat/day

<7-10% from saturated fat (includes trans fatty acid)

<200-300 mg cholesterol a day