Lipids

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dekupar
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76253
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Lipids
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2011-03-30 16:40:36
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Lipids
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Lipids
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  1. Definiation of lipids
    • a family of biomolecules that have the common property of being soluble in organic solvents but not in water.
    • typically the lipid content of a plant cell can be extracted using an organic solvent such as ether, chloroform, or acetone
  2. Composition of waxes
    fatty acids+ long chain of alcohols
  3. Composition of fats and oils
    fatty acids+ glycerol
  4. Physical properties of fats
    • melting pt- determined by length of the chain & degree of unsaturation
    • saturated- higher mp than unsaturated with same number of carbon atoms
    • more double bonds- lower mp ignoring # of carbons
    • solubility- low in water
  5. Simple lipids
    glycerol+ fatty acid
  6. complex lipids
    alcohol+ fatty acid+ a third component
  7. Hydrolyzable lipids
    these undergo hydrolytic cleavage into two or more considerably smaller compounds in the presence of an acid, a base, or a digestive enzyme. All of these contain at least one ester group
  8. Nohydrolyzable lipids
    these don't undergo hydrolytic cleavage b/c they don't contain an ester or amide, phosphate, or acetal group
  9. Lipid function
    • cell membrane structure
    • energy storage
    • hormones and vitamins
  10. Fatty acid structure
    • long chain monocarboxylic acid
    • size range C12-C14
    • always and even number of carbons
  11. saturated vs. unsaturated
    • saturated- no double bonds
    • unsaturated- one or more double bonds
  12. Bond designation in fatty acids
    18:3
    • 18 tells number of C atoms
    • 3 tells number of double bonds
  13. Delta notation
    the delta sign after the number of double bonds indicates the placement of the double bonds
  14. MUFA
    monounsaturated fatty acids have 1 double bond in the carbon chain
  15. PUFA
    polyunsaturated fatty acid have 2 or more double bonds
  16. amphipathic
    one part of the molecule is hydrophobic and another part is hydrophilic
  17. Structure of fats and oils
    • chemically fats and oils are both esters
    • the alcohol portion is always derived from glycerol and the acid portion is furnished by the fatty acid
    • B/c glycerol has 3 OH groups, a single molecule of glycerol can be bonded to 3 different acid molecules
  18. triglycerides
    • fats and oils
    • a compound formed by the esterfication of three fatty acids to glycerol
  19. Linoleic acid
    • an omega- 6 fatty acid
    • this means that the end most double bond is located 6 carbons from the methyl end of the chain
    • CH3(CH2)4(CH=CHCH2)2(CH2)6COOH
  20. Linolenic acid
    an omega- 3 fatty acid where the end most carbon atom having the double bond is 3 carbons from the methyl end
  21. Olestra
    a synthetic polyester of sucrose and fatty acids passes through the digestive tract unabsorbed
  22. melting points of fatty acids
    • fats- soild at room temp
    • oils- liquid at room temp
    • waxes are solid- ester of a saturated fatty acid and a long chain alcohol containing from 14-30 carbons- serves as a protective coating in feathers
  23. waxes
    • esters of fatty acid and long chain alcohols
    • water insoluble and not easily hydrolyzed
  24. Neutral glycerides
    • ester of glycerol and a fatty acid.
    • principal function is energy storage- fat
    • diagram in note!
  25. esterification of fatty acids
    RCOOH+ROH--> RC(=O)OR+H2O
  26. hydrolysis of fatty acids
    • RC-C(=O)-OR+ H2O-->R-C-OH + ROH
    • important for fat and oil digestion
  27. saponification of fatty acids
    • RCOOH+NaOH-->RCOO-Na++H2O
    • the commerical production of the salt of fatty acids (soap)
  28. reactions of unsaturated fatty acids
    • they can undergo the same reactions
    • will also undergo addition
    • most common addition is hydrogenation
  29. partial hydrogenation
    • not all of the double bonds are converted to single bonds
    • convert the oil into a solid
  30. hydrogenation
    • decreases the degree of unsaturation, used to make margarines from oils
    • now a health concern about the hydrogenation of food products.
    • the problem is that during hydrogenation some of the cis-bonds are converted to trans
  31. summary of reactions
    hydrolysis
    saponification
    esterification
    hydrogenation
    • hydrolysis-->glycerol+ 3 fatty acids
    • saponification: 3 fatty acids+glycerol--> 3 fatty acid salts + 3 water
    • esterification--> triacylglyerol + 3 water
    • hydrogenation--> reduces the degree of PUFAs
  32. oxidation
    • the C-C double bonds present in the fatty acid residues of a triacygylcerol are subject to oxidation with oxygen from the air as teh oxidizing agent
    • producing both aldehyde and carboxylic acid products
    • comerically prepared foods containing fats and oils nearly always contain antioxidants- substances that are more easily oxidized than the food
  33. eicosanoids
    • oxygenated C20 fatty acids that function as a messenger
    • these are "hormone like" molecules rather than true hormones b/c they are not transported in the blood stream to their site of action
    • unsaturated
    • some are essentail fatty acids
  34. Physiological effect of eicosanoids
    • 1.inflammatory response
    • 2.production of paon and fever
    • 3.regulation of blood pressure
    • 4.induciton of blood clotting
    • 5.control of reproduction functions
    • 6.regulation of the sleep/ wake cycle
  35. Prostaglandins
    • all are dervied from arachidoric acid a twenty carbon fatty acid derivation that contains a cyclopentane ring and oxygen containing functional group
    • most of these are synthesized from arachidonic acid by a ring closer at C 8 & 12
    • the enzyme catalyzing this is called cycloxygenase (COX)
  36. COX-1
    catalyzes the normal physiological function
  37. COX-2
    responsibly for the production of prostaglands
  38. Smooth muscle contraction
    prostaglandins stimulate contractions in the reproductive system
  39. GI tract
    • prostoglandins will:
    • inhibit the secretion of hydrocholoric acid in the stomach
    • increase secration of mucus layer
    • protects mucose from acid invasion
  40. NSAID
    block the oxidation of an achidonic acid to form the various classes of eicosanoids (block COX-2)
  41. Leukotrienes
    produced by WBC's in lungs
  42. Thromboxane
    • produced by platelets in blood
    • stimulates constriction of blood vessels
    • Aggreation of platelets
  43. Steroids
    broad class of compounds that all have the same base structure. a nonsaponifiable lipid
  44. Cholesterol
    • most abundant steroid in the human body
    • principal membrane lipid for fluidity
    • insoluble in the aqueous medium of the blood
  45. How does cholesterol become water soluble
    in order for it to be transported from the liver where it is synthesized, to the tissues, cholesterol combines w/ phospholipids & proteins to form small water soluble spherical particles called lipoproteins
  46. What does cholesterol do to the body's arteries
    • LDL supply more cholesterol than is needed, LDLs deposit cholesterol in the wall of arteries forming plaque
    • results in:
    • increased bp from: narrowing of arteries, reduced ability to stretch
    • clot formation leading to: MI, stroke
  47. What is cholesterol used for?
    need for healthy cell membranes and it serves as teh starting material for the synthesis of all other steroids and vit. D
  48. LDLs
    low density lipoproteins transport chloesterol from the liver to the tissue
  49. HDLs
    high density lipoproteins transport cholesterol from the tissue bakc to the liver
  50. Bile Salts
    • emulsifying agents that make dietary lipids soluble in the aqueous environment of the digestive tract
    • these salts are released ino the intestine from the gallbladder
  51. Source for bile salts
    • bile, a fluid secreted by the liver, stored in hte gallbladder, and released into the small intestine during digestion
    • bile salts are cholesterol oxidation products
  52. Sex hormones
    control reproduction and secondary sex hormones
  53. estrogen
    • synthesized in the ovaries and adrenal cortex- the female sex hormone
    • responsible for secondary sex characteristics, onset of puberty, regulation of the menstrual cycle, stimulate the development of the mammary glands
  54. androgens
    • synthesized in the testes
    • responsible for the male scondary sex characteristics
  55. progestins
    • synthesized in the ovaries and the placenta
    • prepare the lining of the uterus for implantation of the fertilized ovum
  56. ALL DONE!!!
    =)

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