fatty acids

fatty acids

1. fatty acids have a carboxyl group at the polar end and a hydrocarbon chain as a non-polar tail.

2. amphiphilic compounds

   • carboxyl group is hydrophilic
   • hydrocarbon tail is hydrophobic

3. types

   • saturated fatty acids
     • palmitic (16;0) and stearic acid (18;0) are the most abundant fatty acids found in animal fat and occur largely in esterfied form (glycerides). fatty acids of 10 carbons or less are not normally found as components of animal lipid. one exception is butyric acid (C3H7COOH) which is found in butter fat of the milk of ruminants
     • only c-c single bonds
   • unsaturated fatty acids
     • their melting points and boiling points are generally lower than those of their saturated counterparts
     • have c-c double bonds of varying numbers - (single - monoenoic) (double - dienoic) (triple - trienoic)
     • the solubility of unsaturated fatty acids in non-polar solvents is normally greater than that of their saturated counterparts
     • all common unsaturated fatty acids are liquids at room temperature
     • monoenic series
       • one double bond
       • members of this series are components of the lipid in prokaryotic membranes
     • dienoic series
       • 2 double bonds
     • shorthand notation= chain length:number of double bonds (postion of double bonds)
     • trienoic series
       • 3 double bonds
     • arachidonic-acid or tetraeonic fatty acid
       • docosahexenoic acid 22:6 (4,7,10,13,16,19)
         • most abundant fatty acid in photoreceptor membranes
       • fatty acids with higher degrees of unsaturation
   • essential and non-essential fatty acids
     • essential fatty acids are those that an organism cant produce on its own; such as linoleic acid and a-linolenic acid which animals have to get from plants
   • eicosanoids
     • fatty acids which are derived from 20 carbon arachidonic acid (20;4), and are polyunsaturated.
     • they exert potent hormone-like actions on various tissues, in which they are produced
     • prostaglandins
       • 20 carbons
       • synthesized in all mammalian cells except red blood cells
       • they are circulating hormones
       • they are not stored in the body
       • are formed in burst responses to certain stimuli
       • contain diverse groups such as keto, carboxyl and hydroxy which are found on the side chains and/or cyclopentane ring.
       • the double bonds are in the trans configuration
       • the letter occuring after the abbreviation PG indicates the nature and position of the oxygen containing substituents present in the cyclopentane ring.
       • the physiological effects elicited by prostaglandins are confusing.
         • they are natural mediators of inflammation for example in arthritis, skin and eye inflammation
           • these effects are inhibited by corticosteroids and non-steroidal anti-inflammatory drugs which act by blocking prostaglandin biosynthesis.
             • other processes involving PGs include water retention, ion transport and modulation of blood pressure.
               • their release in the eye following inflammation or trauma can produce increased vascular permeability or intraocular pressure
                 • some prostaglandins in low topical doses can decrease intraocular pressure and thus have potential in treating glaucoma
     • thromboxanes
       • first isolated from blood platelets (thrombocytes)
       • they have a six carbon ring containing an ether
       • they are produced by platelets and act in the formation of blood clots and the reduction of blood flow to the site of the clot
     • leukotrienes
       • they are found in white blood cells (leukocytes)
       • they have 3 conjugated bonds (trienes)
       • in LTA4
         • LT = leukotriene
         • A = nature and postion of the O2 containing constituent
         • 4 = number of double bonds
       • functions:
         • result in constriction of smooth muscle especially in lungs. asthma attack may result from this constricting action since synthesis of leukotriene C appears to be facilitated by allergic reactions. drugs that inhibit synthesis of LTC4 show promise for treatment of asthma reducing the need for inhalers
         • they may have inflammatory properties involved in rheumatoid arthritis
         • strong contraction of the smooth muscle of the lung that occurs during anaphylactic shock is part of the potentially fatal allergic reaction in individuals hypersensitive to bee stings, pencillin or various other agents