medical chemistry (2) part ii (lipids) week 5 lectures 1435-36 glycerides,non-glyceride lipids...
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Medical chemistry (2)Part II (Lipids)
week 5 lectures1435-36
Glycerides ,Non-glyceride lipidsMembranes Lipids
Taif UniversityCollege of Medicine
Preparatory Year Students
Lectures outlines
Definition and importance of lipids
Classification of lipids
Fatty acids structure and properties
Important reactions of FA
Glycerides
Non-glyceride lipids
Membranes Lipids
Phospho-glycerides
Phospho-glycerides
A glycerophospholipid is a lipid that contains two fatty acids and a phosphate group esterified to a glycerol molecule and an alcohol esterified to the phosphate group.
Glycerophospholipids
Phosphatidyl ester
Phosphatidyl ethanolamine(cephalin)
Phosphatidyl choline(lecithin-emulsifier)
Phosphatidyl serine
Phospho-glyceridesPhosphoLipids
inositol
The Importance and functions of phospholipids are :
1- Amphipathic molecules they form micelles in water.
2- Good emulsifying factors.3- Lung surfactant mainly of dipalmitoyl-lecithin, the lack of which is responsible for respiratory distress syndrome
in premature infants.
4- Prevent deposition of cholesterol (biliary calculi).5- Constituents of lipid bilayer in cell membranes6- Provide arachidonic acid for synthesis of
eicosanoids.7- Essential for blood clotting, as they provide the
platelet activating factor (PAF)
Lipids Classification
Eicosanoides
Nonglyceride Lipids A- Sphingolipids
Sphingolipids are derivatives of ceramide (an amide between a fatty acid and sphingosine) and an amino alcohol.
Ceramide Structure
Sphingolipids
Sphingophospholipids(Sphingomyelins )
Sphingoglycolipids(Cerebrosides &
Gangliosides)
Sphingomyelins
Fatty acid
Phosphate groupCholine
• present in cell membranes specially of the lungs and brain mainly in the myelin sheath
. It contains sphingosine (sphingol) which is 18 carbon amino alcohol fatty acids are linked to sphingosine to form ceramide, which is connected to phoshocholine to form sphingomyelin.
Sphingoglycolipids
are carbohydrate-containing ceramide derivatives (in the outer face of plasma membranes)
Glycosphingolipids at the cell surface are sites of recognition.They found mainly in the myelin sheath and cell membrane of RBCs. They act as cell membrane receptors for hormones and external stimuli. They provide recognition properties.
Cerebrosides(Monosaccharide)
Gangliosides(Oligosaccharide)
Nonglyceride Lipids
Gangliosides
Oligosaccharide linked to ceramide
Example:blood group
identification
Glucocerebrosides occur in the plasma membrane of non-neuronal cells
Galactocerebrosides occur in the plasma membrane of neurons
Cerebrosides
Nonglyceride Lipids: B-Steroids
CholesterolCholesterol is a C27 steroid molecule that is:
a component of cell membranesa precursor for other steroid-based lipids:
bile acidssteroid hormonesVitamin D3 (cholecalciferol) Blood level of cholesterol: ranging from 100 to 200 mg/dL (30% as free cholesterol and 70% as cholesteryl esters) Hazards of hyperchosterolemia: Increased plasma level of cholesterol predisposes to atherosclerosis and coronary heart diseases.
Steroid Hormones• Are Oxidized
cholesterol derivatives
• Function as:• sex hormones• metabolic
regulation• Anti-
inflammatory compounds
glucose metabolism,salt excretion (adrenalgland)
female sex hormone(ovaries, placenta)
male sex hormone (testis
antiinflammatory compounds
Bile acids• A bile acid is a cholesterol derivative that
functions as a lipid-emulsifying agent in the aqueous environment of the digestive tract.
• Obtained by oxidation of cholesterolFunctions: • Conversion of cholesterol
to bile salt is an important mechanism for removal of excess cholesterol from blood.
• prevent precipitation of cholesterol
• They are good emulsifying factors important for digestion and absorption of fats.
Lipids Classification
Eicosanoides
Nonglyceride Lipids C) Waxes
• Are esters of long-chain fatty acids with long-chain alcohols (a very high melting point)
Example:Triaconoylpalmitate,a major component of bees wax
Functions:•energy stores•water-repellent
Nonglyceride Lipids : D-Eicosanoids Eicosanoids are important regulatory molecules Referred to as local regulators (Function where they are
produced). Three classes: Prostaglandins, Thromboxanes, and
Leukotrienes Prostaglandins – mediate pains sensitivity, inflammation
and swelling Thromboxanes – involved in blood clotting, constriction
of arteries Leukotrienes – attract white cells, involved
inflammatory diseases (asthma, arthritis, etc..)
ProstaglandinsProstaglandins have:20 carbon atoms in their fatty acid chains.An OH on carbon 11 and 15.A trans double bond at carbon 13.
Prostaglandins in the BodyProstaglandins are:
• Produced by injured tissues.
• Involved in pain, fever, and inflammation.
• Not produced when anti-inflammatory drugs such as aspirin inhibit their synthesis.
For more information about prostaglandins please visit:
http://www.elmhurst.edu/~chm/vchembook/555prostagland.html
Biomembranes
Biomembranes
Lipid Structure
• Hydrophilic head – H2O loving – due to polar group in the head
• Hydrophobic tail – H2O hating – due to the long hydrocarbon tails
Membrane Lipidshy
drop
hobi
c fa
tty
acid
tail
hydrophilic head
General characteristics of membrane lipids
Structure of phospholipids
hydr
opho
bic
fatt
y ac
id c
hain
s
hydrophilic head
Membrane Lipids
A space-filling model of a typical phospholipid bilayer
Because their fatty acid tails are poorly soluble in water, phospholipids spontaneously form bilayers in aqueous solutions, with the hydrophobic tails buried in the interior of the membrane and the polar head groups exposed on both sides, in contact with water
Important Classes of Lipids
Glycerol backbone Sphingosine backbone
Question
To which class of lipids belong the following molecules?
A B C
D E F
G H
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