LECTURE                                      LIPIDS

INTRODUCTION:
The primary role of lipids is forming cell membranes, the bilipid layer common to all living things bacteria and human.  Through evolution lipids have been put to use as storage of energy in the form of fats and oils.  An extremely important role of lipids is the further evolution into more complex structures such as cholesterol and other biologically active molecules.

After this lecture you will:

  • understand the structure of lipids
  • see how lipids are created from glycerol and fatty acids
  • learn what essential fatty acids are
  • learn how cell membranes are made from lipids-triglycerides
  • understand the role of cholesterol and how it is made
  • find out what other biologically active molecules are made from lipids
  • LIPIDS (fats and oils): TRIGLYCERIDE FORMATION (JAVA)
    Fats and oils are both lipids.  However, by convention liquid lipids are called oils and solid lipids are called fats.
    From carbohydrates comes sugars and glycerin AKA glycerol
     

    LIPIDS start with a "frame" of a triple alcohol 

    (that OH is the alcohol part) calledglycerol


    http://www.chemistryland.com/ElementarySchool/BuildingBlocks/BuildingOrganic.htm
    THEN, long chains of fatty acids are added to each OH by dehydration synthesis

    (an acid means a COOH is on one end)


    http://www.chemistryland.com/ElementarySchool/BuildingBlocks/BuildingOrganic.htm
    Put the glycerin and fatty acids together by dehydration synthesis (remove a water) and get...........

    Saturated and unsaturated fatty acids, cis and trans fatty acids click HERE

    What is wrong with trans fatty acids

    TRIGLYCERIDES
    http://www.chemistryland.com/ElementarySchool/BuildingBlocks/BuildingOrganic.htm
    GO HERE TO WATCH THE FORMATION OF TRIGLYCERIDES
    ESSENTIAL FATTY ACIDS
    They are called "essential" because we must eat them.  We cannot make all the different lengths of fatty acids we need.  Two of these are:

    1. linoleic acid (omega-6) 

    2. alpha-linolenic acid (omega-3)

    They are essential because they are precursors for molecules that regulate numerous body functions including blood pressure, blood viscosity, vasoconstriction, immune and inflammatory responses

    MORE READING HERE.  IT IS NECESSARY TO BE CAREFUL SINCE THERE IS A LOT OF SELLING GOING ON ABOUT THIS TOPIC.


     
    PHOSPHOLIPIDS
    phospholipid has two, rather then three, fatty acid chains attached to a glycerol molecule.
    - a phosphate (PO4) is in place of the third chain attached to a CH2-CH2-N- (CH2)3
    - is negatively charged and interacts nicely with water (hydrophilic)
    -- the fatty chains are hydrophobic and don't interact with water.
    - when simply dumped into water phospholipids form single layers, double layers AKA bilipid layer or spheres (called micelles) with the heads oriented toward the water and the tails oriented away from it.

    - double phospholipid layers forms a barrier with an outside and an inside.. this is essential for a cell because it keeps stuff inside and other stuff outside in a liquid environment

    -- cell membranes must be flexible. This is possible because the phospholipids are not chemically bonded together, rather they stay together because of the hydrophilic and hydrophobic interactions.

    - The greater the concentration of unsaturated fatty acid tails in the phospholipids the more fluid is the membrane. 

    - The double bond in the fatty acid prevents the fatty acid tails from packing tightly together.
     


     
    CHOLESTEROL AND OTHER BIOLOGICALLY ACTIVE MOLECULES MADE FROM LIPIDS
    CHOLESTEROL
    - has a ring structure (pic)
    -- is a major component of cell membranes
    - helps to 'pack' phospholipids giving more rigidity to the membranes
    -- it is converted to vitamin D (if irradiated with UV)
    -- can be modified to form steroid hormones
    -- is modified to bile acids to digest fats
    - your body makes cholesterol whether or not you eat it
    STEROIDS
    -- Steroids are REGULATORY molecules
    -- sex hormones estrogen and testosterone and vitamins A, D, and E.

    VITAMINS AND MINERALS
    -- some enzymes require small organic molecules called cofactors in order to function properly. Vitamins are the source of these cofactors.
    -- Vitamins A, D, E, and K are soluble in fat and are stored in fat, the rest are water soluble
    - vitamins like folic acid are required for DNA repair
    -- The body requires inorganic elements "minerals."
    -- Calcium and potassium are found in bones and teeth.
    -- Sodium and potassium are essential in the operation of nerve cells.
    -- Sulfur is found in proteins, magnesium is a constituent of enzymes, zinc is a coenzyme, and iodine is a component of the thyroid hormone.
    -- Iron and copper are necessary for hemoglobin.
    - too much of some of these minerals can cause problems

    VITAMINS                  PURPOSE
     A                                vision, differentiation
     Ascorbic Acid          collagen formation
     Biotin                       carboxylation
     Cobalamin               homocysteine metabolism
     D                               Ca metabolism
     E                               antioxidant
     Folic Acid                purine synthesis
     K                              blood coagulation
     Niacin                      oxidation-reduction
     Pantothenic Acid   carrier of activated acyl, acetyl groups
     Pyridoxine              transamination
     Riboflavin               oxidation-reduction
     Thiamine                 oxidative decarboxylation

    REVIEW QUESTIONS:
    What is the difference between fats, oils and lipids?
    What kind of structure does lipids form?
    What kind of regulatory molecules are made from lipids?
    What is the difference between a solid oil and a liquid oil?
    What two kinds of molecules make up tri-glycerides?
    What is glycerol used for in the body?  Fatty acids?
    What three kinds of molecules make up phospholipids?  What is it used for?
    What is dehydration synthesis?
    What are 3 functions of cholesterol?
    What are steroids?
    Why are vitamins and minerals needed?