Simple lipids


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Simple lipids

  2. 2. • Lipids are a heterogamous group of chemicalcompounds including:• Fats• Oils• Waxes• Steroids• Other related compounds[they are related more by their physicalproperties than their chemical properties.]2
  3. 3. Common properties of lipids:• Relatively insoluble in water.• Soluble in nonpolar solvents such as:–Ether .–Chloroform.–Benzene.–Acetone.3
  4. 4. Lipids are important dietary constituents:• High energy value.• Essential fatty acids.• Fat soluble vitamins [ A D E K].4
  5. 5. • Lipids are stored in adipose tissue• It serves as thermal insulator• Nonpolar lipids serve as electrical insulator innerves.• Lipids and proteins (Lipoproteins) are importantconstituents of cell and mitochondrialmembranes.• Lipoproteins serve as means of transport of lipidsin blood.5
  6. 6. Knowledge of lipids biochemistry is necessary inunderstanding many important biochemical areas e.g.:Obesity.Diabetes mellitus.Atherosclerosis.Nutrition: role of polyunsaturated fatty acids and fatsoluble vitamins.etc……6
  7. 7. Classification of lipids:• Simple lipids.• Complex lipids.• Precursor and derived lipids.7
  8. 8. Classification of lipids:1. Simple lipids:They are esters of fatty acids with alcohols:1. Fats and oils: esters of fatty acids with glycerol(triacylglycerols).2. Waxes: esters of fatty acids with high molecularweight monohydric alcohol.8
  9. 9. 2. Complex lipids:Esters of fatty acids with alcohols and molecules withother groups.Phospholipids:Lipids containing:Fatty acidsAlcoholPhosphoric acid residue.Glycolipids (glycosphingolipids):Lipids containing:Fatty acidSphingosineCarbohydrate.9
  10. 10. 3. Precursor and derived lipids:• This group includes:–Fatty Acids.–Glycerol.–Cholesterol.–Steroid hormones.–Fatty aldehydes.–Fat soluble vitamins [ A D E K].–Some other alcohols.10
  11. 11. Esters ofAlcohols and Carboxylic Acids11RC OHOCarboxylic Acid Alcohol EsterR OHR C O RO
  12. 12. Triacylglycerols in Simple Lipids12
  13. 13. Fatty Acids• Fatty acids (FAs) exist as:• Esterified fatty acids:Fatty acids occur mainly as esters in natural fatsand oils (Triacylglycerols).• Free fatty acids (FFA).13
  14. 14. • more than 90% of FAs found in plasma are in theform of FA esters.– Triacylglycerols (triglycerides).– Cholesterol esters– PhospholipidsALL are contained in lipoproteins.• Unesterified FAs are circulated in association withalbumin.14
  15. 15. Physiological Functions of Fatty Acids:• Energy Source: During fasting, blood level of FFAincreases.• FAs can be oxidized by many tissues including liverand muscle to produce energy.• FAs are structural components of membrane lipids.• FAs are attached to some intracellular proteins.• FAs are precursors of hormone-like prostaglandins.• FAs esterified as TAGs stored in adipose tissue serveas major energy reserve in the body.15
  16. 16. Structure of Fatty Acids:• FAs consist of:– Hydrophobic hydrocarbon chain.– Carboxyl group. The anionic group has an affinity for water giving theFA its amphipathic nature, having both a hydrophilicand a hydrophobic regions. Long chain fatty acids (LCFA) are highly water insoluble,hence they need transport in blood through plasmaalbumin.16
  17. 17. Structure of a fatty acid.17
  18. 18. • the carbons in FAs are named as follows:– Carbon atoms are numbered from the carboxylcarbon (carbon no. 1).– C-2, the carbon at which the carboxyl group isattached also called: α- carbon.• C- 3 : β- carbon• C- 4: γ- carbon18
  19. 19. 19126 5 4 3
  20. 20. – Carbon of the terminal methyl group is known as ω-carbon.– The carbons of FAs can be counted beginning at theω-carbon or methyl end of the chain.– ω9 indicates a double bond between the 9th and the10th carbons counting from ω- carbon.– Arachidonic acid is called ω-6 FA.– Δ is used for indicating the number and position ofthe double bonds,• Δ9 indicates double bond between C9 and C10 of a fattyacid. 20
  21. 21. • In animals, additional double bonds areintroduced only between the existing doublebonds e.g.:– ω9– ω6– ω3– Leading to a series of fatty acids known as:ω9, ω6 and ω3 fatty acids.21
  22. 22. Chain length of FAs:• FAs are denoted as follows:• Ex: Arachidonic acid 20:4(5,8,11,14)– The number before the colon indicates thenumber of carbons in the chain.– The numbers after indicates the number andpositions of double bonds.22
  23. 23. Arachidonic acid23
  24. 24. • Fatty acids that occur in natural fats are always straightchain derivatives containing an even number of carbonatoms.• Fatty acids are named after corresponding hydrocarbonswith the same number and arrangements of carbonatoms.• oic been substituted for –e.• Saturated acids end in –anoic.• Unsaturated acids end in –enoic.24
  25. 25. Some fatty acids of physiologic importance 25
  26. 26. Saturation of Fatty AcidsSaturated Fatty Acids:• Saturated FAs: contain no double bonds.• Short chain saturated fatty acids have lowmelting point.• Short chain saturated fatty are liquid at roomtemperature.• Medium and long chain fatty acids have highmelting point.• Medium and long chain fatty acids are solid atroom temperature.26
  27. 27. S aturated fatty acids (all have C–C single bonds):27
  28. 28. Unsaturated Fatty Acids:• Unsaturated FAs: contain one, or more doublebond, being:1. Monounsaturated FAs.2. Polyunsaturated FAs.• Double bonds are nearly always in cis- ratherthan trans- position.• Double bonds are always spaced by 3 carbons.28
  29. 29. 29
  30. 30. Unsaturated Fatty acidsHave nonlinear chains that do not allow molecules to packclosely.Have low melting points, are liquids at room temperature.30
  31. 31. (CH 2)7C O HOomega-6 fatty acid(linoleic acid)(C H 2 )7 C O HO6ω1ω1omega-3 fatty acid(linolenic acid)Polyunsaturated Fatty acids:Polyunsaturated fatty acids such as:Linoleic acidLinolenic AcidAre nutritionally essential fatty acids31
  32. 32. Sat. Fatty Acids Formula Melting Point (oC)Butyric C4H8O2 LiquidPalmitic C16H22O2 63Stearic C18H36O2 70Unsat. Fatty Acids Formula Melting Point (oC)Oleic C18H34O2 LiquidLinoleic C18H32O2 LiquidLinolenic C18H30O2 LiquidMelting point of some saturated andunsaturated fatty acids32
  33. 33. - A fat is a triacylglycerol that is solid at room temperature- An oil is a triacylglycerol that is liquid at room temperature- Usually fats come from animal sources and contain moresaturated fatty acids- Oils come from plant sources and have a high content ofunsaturated fatty acidsFats and Oils33
  34. 34. THANKS34