LIPIDS

LIPIDS

lip= fat

   - Makes up 18 - 25 % of body mass in lean adults.

   -Contain CARBON, HYDROGEN and OXYGEN.


But they do not have a 2:1 ratio of hydrogen to oxygen 

LIPIDS ARE HYDROPHILIC

The proportion of electronegative oxygen atoms in lipids is usually smaller than carbohydrates.

      - so there are fewer polar covalent bonds.
  As a result , most lipids are insoluble in polar solvents such as water.

Only the smallest lipids (some fatty acids ) can dissolve in watery blood plasma.

LIPOPROTEINS

To become more soluble in blood plasma, lipidn molecules join with hydrophilic protein molecules.

The resulting lipid- protein complexes are called lipoproteins.



  -Are soluble 
     - because proteins are outside and 
                    lipids are on the inside.


LIPID FAMILY

1. FATTY ACIDS

2. TRIGLYCERIDES

3. PHOSPHOLIPIDS

4. STEROIDS

5. EICOSANOIDS

6. OTHERS


1. FATTY ACIDS

   - Used to synthesize triglycerides and phospholipids.

   - catabolized to generate ATP.

   - consists of 

                          - a carboxyl group
                                    and
                          - a hydrocarbon group chain.

   - can be either saturated or unsaturated.

1. SATURATED FATTY ACID

    - Contains only single covalent bond between carbon atoms of the hydrocarbon chain.

Because they lack double bonds, each carbon atom of hydrocarbon chain is saturated with hydrogen atom.

eg.  Palmitic acid   C15H31COOH.

2. UNSATURATED FATTY ACID

Contains 
1 orv more double covalent bonds between carbon atoms of the hydrocarbon chain.

Thus the fatty acid is not completely saturated with hydrogen atoms.

eg.  Oleic acid  C17H33COOH

The unsaturated fatty acid has a KINK/ BEND at the site of the double bond.

MONOUNSATURATED FATTY ACID

 If fatty acid has just 1 double bond in hydrocarbon chain.

eg. Oleic acid.

POLYUNSATURATED FATTY ACID - PUFA


 If fatty acid more than  1 double bond in hydrocarbon chain.

  - contains more than a kink / bend

eg. Omega-3 fatty acids




FATTY ACIDS IN HEALTH AND DISEASE


ESSENTIAL FATTY ACIDS

 - A group of fatty acids essential to human health

 - Cannot be made by human body.

 - Must be obtained from foods or supplements.

MOST IMPORTANT ESSENTIAL FATTY ACIDS

1. OMEGA-3 FATTY ACIDS

2. OMEGA-6 FATTY ACIDS

3. cis- FATTY ACIDS



OMEGA-3 and OMEGA-6 FATTY ACIDS

   -Poly unsaturated fatty acids

   -Believed to work together to promote health.

1. may have a protective effect against heart disease and        stroke.

     -  by lowering total cholesterol

     - raising HDL / good cholesterol.

     - lowering LDL / bad cholesterol.

2. Decrease bone loss

     - by increasing calcium utilization by body.

3. Reduce symptoms of arthritis due to inflammation

4. Improve certain skin disorders

                                       - psoriasis
                                       - eczema
                                       - acne

5. Improve mental functions.


PRIMARY SOURCES OF OMEGA-3 FATTY ACIDS

   - Flax seed

   - Fatty fish

   - Fish oils

   - Walnuts

   - Oils that have large amounts of poly unsaturated fatty acids.


PRIMARY SOURCES OF OMEGA-6 FATTY ACIDS

   - Processed foods
                      - cereals
                      - breads
                      - white rice

   - Baked goods

   - Eggs

   - Oils that have large amounts of poly unsaturated fatty acids.

   - Meat especially organ meats such as liver.


CIS- FATTY ACIDS

                                            

- An unsaturated fatty acid with with hydrogen atom on either side of the double bond are on the same side of the unsaturated fatty acid

   - are nutritionally beneficial.

   - used by the body to produce hormone like regulators and cell membrane


When cis- fatty acids are heated , pressurized and combined with a catalyst (usually nickel) by hydrogenation

        - they are changed to unhealthy trans- fatty acids


TRANS- FATTY ACIDS

Hydrogen atoms are on opposite sides of the double bond of an unsaturated fatty acid

Hydrogenation is used by manufacturers to make vegetable oils solid at room temperature

                             -and less likely to turn rancid.

Hydrogenated / trans- fatty acids are common in 

     - commercially baked goods
          - crackers
          - cakes
          - cookies

     - salty snack foods

     - some margarine's

     fried foods- donuts, french fries

When oil is used fro frying, and if the oils reused,

     - cis- fatty acids are converted to trans- fatty acids.

If a product label contains the word hydrogenated or partially hydrogenated,
   
     - then the product contains trans - fatty acids




ADVERSE EFFECTS OF TRANS- FATTY ACIDS



1. Increase in total cholesterol.

2. Decrease in HDL.

3. Increase in LDL.

4. Increase in triglycerides.

5. Increase risk of heart diseases and other cardio-vascular diseases.



2. TRIGLYCERIDES / TRIGLYCEROLS

tri=3

The most plentiful lipids in our body and diet.

   - consists of 2 types of building blocks.

   - a single glycerol molecule

   - 3 fatty acid molecules.


   - a 3- carbon glycerol molecule forms the backbone of a triglyceride.

     - 3 fatty acids are attached by Dehydration synthesis reactions
                    - one to each carbon of the glycerol backbone.

   - The chemical bond formed  where each water molecule is removed is an ester linkage


The reverse reaction- HYDROLYSIS- 
           - breaks down a single molecule of a triglyceride into 3 fatty acids

                              HYDROLYSIS
TRIGLYCERIDES      -    3 FATTY ACIDS


FUNCTIONS

   - Body's most  highly concentrated form of chemical energy .

   - provide more than twice as much energy per gram as do carbohydrates and proteins.

   - Our capacity to store triglycerides in adipose tissue is unlimited for practical purposes.

   - Excess carbohydrates,  proteins, fats and oils are deposited in adipose tissues as triglycerides.


FAT

Triglycerides that us solid at room temperature.

 - Fatty acids of a fat are mostly saturated.

   - these lack double bonds in their hydrocarbon  chains,

      - they can closely pack together and solidify at room temperature.

SATURATED FAT

- A fat that mainly consists of saturated fatty acids.

   - Occur 
       - mostly in meats especially red meats.

       - nonskim dairy products
                                     - whole milk
                                     - cheese       
                                     - butter


       - in cocoa butter
       - palm oil
       - coconut oil


Diets that conatin large amounts of saturate dfats are associated with disorders sucha s heart disease and colorectal cancer.


OIL

Triglycerides that is liquid at room temperature .

-Fats of oil are mostly unsaturated.

The kinks at the sites of the double bonds prevent unsaturated fatty acids of an oil from closely packing together and solidifying.

   The fatty acids of an oil can be either 
       - monounsaturated 

                  OR

       - polyunsaturated


MONOUNSATURATED FATS

   - Contain triglycerides with monounsaturated fatty acid.

eg.
   olive oil
   peanut oil
   canola il
   most nuts
   avocados


POLYUNSATURATED FATS

   - Contain triglyceride that mostly consist of polyunsaturated fatty acids.

eg.

   corn oil
   safflower oil
   sunflower oil
   soyabean oil
   fatty fish - salmon
                 - tuna
                - mackerel

Both monounsaturated  and polyunsaturated fats are believed to decrease the risk of heart disease.


3. PHOSPHOLIPIDS

- Lipids that contain phosphorus.

- Major lipid component of cell membrane.

- Have a glycerol backbone
            and  

   2 fatty acid chains attached to the first carbon atom


HEAD POSITION

   -In the third position a phosphate group (PO4 3-) links a small charged group that usually contains nitrogen to the backbone.

   -Is polar.

   - Can form hydrogen bonds with water molecules.

TAIL POSITION

 - the 2 fatty acids

   - Non polar

   - Can interact only with other lipids.

AMPHIPATHIC

amphi= on both sides
-pathic= feeling

   - Molecules that have both polar and non polar parts.

   - Amphipathic phospholipids line up tail to tail in a double row to make up much of the membrane that surrounds each cell.


4. STEROIDS

- Lipids that have 4 rings of carbon atoms.

- Body cells synthesize other steroids from cholesterol
    - which has a  large non polar region.

- consists of 4 rings and a hydrocarbon tail.

'
COMMON STEROIDS IN BODY

These are known as STEROLS 
                - because they also have at least 1 hydroxyl(alcohol) group -OH.

The polar hydroxyl groups make sterol weakly amphipathic.  



a. CHOLESTEROL

   -Minor component of all animal cell membranes.

   - Precursor of bile salts
                        Vitamin D
                        steroid hormone

b. BILE SALTS

- Needed for lipid digestion
   and absorption of dietary lipids.

c. Vitamin D

 - Helps to regulate calcium level in body.

 - Needed for bone growth and repair.


d. Adrenocortical hormones

 -Help regulate metabolism
                        resistance to stress
                        salt and water balance.

eg.

Cortisol- for maintaining normal blood sugar levels.



e. SEX HORMONES

- Stimulate reproductive functions  and sexual characteristics

eg.  estrogen 
       testosterone



5. EICOSANOIDS

eicosan= 20

- Lipids derived from a 20 carbon fatty acid called arachidonic acid.



2 PRINCIPAL CLASSES

A. PROSTAGLANDIN

B. LEUKOTRIENES


  A. Prostaglandin

  - a. modify responses to hormones.

  - b. contributes to inflammatory response.

  - c. influence formation of blood clots.

  - d. regulate body temperature.

  - e. dilate air ways to the lungs.

  - f. prevent stomach ulcers.

  
 B. Leukotrienes

   - participate in allergic and inflammatory responses.




6. OTHERS

A. FAT SOLUBLE VITAMINS

B. LIPOPROTEINS



a. FAT SOLUBLE VITAMINS



   1. CAROTENES


   - Yellow - orange pigments in egg yolk
                                                 carrots
                                                 tomatoes


    - needed for synthesis of Vitamin- A

    - functions as anti oxidants.


    2.  VITAMINS A,D,E,K


a. VITAMIN-A


    - Used to make visual pigments in the eye.



b. Vitamin D

   - Helps to regulate calcium level in body.

   - Needed for bone growth and repair.

c. VITAMIN- E

   - Promotes wound healing.

   - prevents tissue scarring.

   - contributes to the normal structure and function of nervous system.

   - functions as an antioxidant.


d. VITAMIN-K


   - Required for synthesis of blood clotting proteins.



B. LIPOPROTEINS

  -Transports lipids in the blood

 - Carry triglycerides and cholesterol to tissues.

 - Remove excess cholesterol from the blood.