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					Department of Biochemistry
Foundation Module Phase - 1
                     Lipids
Soluble in non-polar solvents and insoluble in polar
solvents. Lipids are not polymers.
                      Fatty acids
•They are basic building blocks of lipids(simplest lipids).
•Fatty acids are carboxylic acids.
Q.Fatty Acids are
amphipathic
molecules. Why?




                     A.Because they have both
                    polar(hydrophilic) and non-
                    polar(hydrophobic) portions
                          in their structure
Classification of fatty acids

                 Fatty
                 acids


     saturated         unsaturated




            monounsaturated    polyunsaturated
  Q. What is the chemical
difference between saturated
and unsaturated fatty acids?



                               A. Saturated fatty acids
                                 contain only single
                               bonds between carbons,
                                 whereas unsaturated
                                fatty acids contain at
                               least one double bond.
Corn oil contains 86% polyunsaturated fatty acids
Therefore is a liquid at room temperature.




    Olive oil contains monounsaturated fatty
    acids.
    Therefore is a liquid at room temperature,
    likely to solidify when refrigerated.



Saturated fatty acids (tropical oils, animal
fats) are solids, or nearly solids at room
temperature.
Unsaturated fats are preferred over saturated fatty
acids for nutritional reasons.


   Q.Would you expect a deep sea fish (living in cold
   water) or a shallow water fish (living in warmer
   water) to have a higher percentage of unsaturated
   fatty acids in its tissues?




                                   A. deep
                                   sea fish
Q1.Give some examples for simple
lipids      Fatty acids + Alcohol




Q2.Find out some common examples
for complex lipids
             Fatty acids + Alcohol+ X
 The degree of saturation of a fatty
acid affects particularly the fatty acid
            melting point.


   Q3.Unsaturated fatty acids have lower
   melting points than saturated fatty acids.
   Why is that?
Melting Points and Solubility in Water
            of Fatty Acids

                                Melting Point




                               Solubility in H2O

                Chain Length
                               A. Fatty acids
                                 which have to be
                                 obtained from
   Q. What are                   food, as human
     essential                   cells have no
   fatty acids?                  appropriate
                                 enzymes
                                 required to
                                 produce them
                                 internally.




Q4.What are the two families of essential
fatty acids?
Good sources of ‘omega-3 fatty acids’

• Oily fish
  (salmon, mackerel, sardines, tuna)
• Pumpkin seeds, sesame seeds
• soybean oil
Good sources of ‘omega-6 fatty acids’
•Most vegetable oil, Sunflower oil, Corn oil, Soybean oil
•Cotton seeds oil
•Pumpkin seeds
•Nuts and cereals
•Poultry, eggs
•Avocado
Essential fatty acids are used by every cell
 in your body.




          Q5.Why are
         essential fatty
         acids good for
             you?
      Lipids have four major functions which
      are physiologically important for human.




                      Serve as vitamins and hormones.




Structural components of biological membranes.



                        synthesize bile acids that
                                    aid
                           lipid solubilization




     Provide energy
                     Glycerides
Glycerides (acylglycerols) are esters formed from glycerol
and fatty acids.
Q6.What elements are
 found in lecithin and
    sphingolipids?
Q7. Identify a-j
Q8.What are
Eicosanoids?
                             A


                             B




Q9.Name the enzymes A& B.
State the mechanisms by which aspirin and
ibuprofen inhibit PGH2 Synthesis.
                      Steroids

•General structure of a steroid – four rings




  Q10.What are the
derivatives of steroids?
      Cholesterol

• Most abundant steroid in the body
• Add methyl CH3- groups, alkyl chain,
  and -OH to steroid nucleus
Cholesterol in the Body,


   • Cellular membranes
   • Myelin sheath, brain,
     and nerve tissue
   • Bile salts
   • Hormones
   • Vitamin D
Q11 . Identify each lipid as: (1) phospholipid (2) steroid
(3) triglyceride (4) sphingolipid

 A. Cholesterol
 B. Glycerol, 2 fatty acids, phosphate, and choline
 C. Sphingosine, fatty acid, phosphate, and choline
 D. Estradiol
 E. Bile salts
 F. Most of plasma membranes
The diagram represents a phospholipid molecule




  Q12.Name the following parts of the molecule
     (i)     A

     (ii)    B

     (iii)   C
         1.Saponification Value

What are the main ingredients in your soap?
    • One test tube is filled with Sunflower oil (A).
    • Coconut oil is placed in a second test tube.(B)
    • Add few drops of Hubl’s iodine for each solution.
    • Test tubes are shaken.
    • After some minutes a spatula full of starch powder is added
      to each of the two test tubes.
    • The test tubes are again shaken.



                            A              B




Q13.what is the
observation?
Foods prepared with edible oil develop a kind of smell
and undergo changes in taste after some time. What is the
reason for this?
                      Rancidity

       Hydrolytic                    Oxidative

Partial hydrolysis of TAG        Oxidation of UFA @double
                                 bond positions.
FFA                 Glycerol
                    (mono/di)              Peroxides

                                Aldehyde               Ketones

                    Objectionable
                    odour + Taste
Health issues associated with lipids
                  Trans fat
•Unsaturated fat with trans-isomer fatty acid.
•Not essential fatty acids

•Naturally found in animal products where they are
produced by bacteria in the gut of ruminant animals (eg:
cow, goat, sheep)
•Therefore some trans fatty acids are present in meat,
milk and other dairy products.
•These are mostly C18 monounsaturated fatty acid
(vaccenic acid).
• Daily intake of 5g trans fat increases the risk of heart
disease by 25%
Trans fatty acids
 are commonly
  found in…..
   How are trans fats made
        artificially?


                     Trans fats are made through the chemical
                     process called hydrogenation of vegetable oils.
                     Hydrogenation solidifies liquid oils and
                     increases the shelf life and the flavour stability
                     of oils and foods that contain them.




Sun flower oil                             Margarine
ANSWERS
a.Fats: Fatty acids + Glycerol


b. Waxes: Fatty acids + Long chain alcohol
      Example             Fatty acids    Alcohol        X
a.Phospholipid            Fatty acids   Alcohol    Phosphoric
ex:                                                acid residue
1.Glycero phospholipid    Fatty acids   Glycerol
                                                   Phosphoric
ex: Lecithin                                       acid residue
                          Fatty acids   Glycerol   Choline

2.Sphingophospho lipid Fatty acids      Sphingosin Carbohydrat
                                        e          e
b.Glycolipids(Glycosphi
ngo lipid)
Presence of one or more double bonds in hydrocarbon chain of unsaturated fatty acids
results “ BENDS” in the molecules. These molecules do not stack well. As a result of that
inter-molecular interactions become much weaker than saturated fatty acids leading to
lower melting points.
1. ω-3 (or omega-3 or n-3)
2. ω-6 (omega-6, n-6.)

•   Alpha-linolenic acid – a polyunsaturated omega-3 fatty acid

•   Linoleic acid -an unsaturated omega-6 fatty acid.
• Control immune system, blood pressure, nervous system,
  inflammatory reactions, blood clotting and hormonal
  functions.
• Regulate a large number of mechanisms including
  increasing the fluidity of cell membranes and improving the
  ability of selective permeability and help to keep toxin out
  and bring nutrients into cells.
• Influence the activation of cell genes and act as second
  messengers and produce good eicosanoids.
• Furthermore, a diet rich in EFAs can be helpful in many
  diseases( Rheumatoid arthritis, Inflammatory bowel disease)
Lecithin
•   a: Oligosaccharide
•   b: Glycoprotein
•   c: Glycolipids
•   d: Head of phospholipid
•   e:Tail of phospholipid
•   f: Phospholipid bilayer
•   g: Filament
•   h:Peripheral protein
•   i: Cholesterol
•   j: Transmembrane protein
Eicosanoids are a family of powerful, hormone-like
compounds
produced in the body from essential fatty acids . . .



• They have specific effects on target cells close to their site of
  formation.
• They are rapidly degraded, so they are not transported to
  distal sites within the body.

• Examples: prostaglandins, prostacyclins, thromboxanes,
  leukotrienes, epoxyeicosatrienoic acids (EETs).
• Roles in inflammation, fever, regulation of blood pressure,
  blood clotting, immune system modulation, control of
  reproductive processes & tissue growth, sleep/wake cycle
  regulation.
A: Lipoxygenase
B:PGH2 synthase

Aspirin and Ibuprofen (a Non-steroid
anti inflammatory drug) Inhibit PGH2
Synthase enzyme.

Note: Aspirin irreversibly acetylates and
thus inactivates the enzyme whereas the
action of Ibuprofen is reversible.
•   Steroid hormones
•   Cholesterol
•   Vitamin D
•   Bile
A.   steroid
B.   phospholipid
C.   sphingolipid
D.   steroid
E.   steroid
F.   phospholipid
Phosphate   Glycerol   2 Fatty acids
group &
N- base
  Observation:
  The sample containing Coconut oil turns intensely blue
  (iodine-starch complex).
  In Sunflower oil all the iodine will be consumed.
  Consequently no colour change can be observed after the
  addition of starch.




Discussion and background:

Sunflower oil contains unsaturated fatty acids.
Iodine adds across the double bonds in an unsaturated bond.
Coconut oil consists mainly of glycerides from saturated fatty
acids (e.g. palmitic and lauric acid).

				
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posted:10/29/2012
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