Ch 11- تفريغ pdf.pdf،،،،،

 Biochemistry of Lipids Objectives: Recognize the features and Functions of different classes of “Lipids” Understand the nomenclature and the physical properties of fatty acids and the relation of these properties to the saturation state of the fatty acids. Recognize t...

 Biochemistry of Lipids Objectives: Recognize the features and Functions of different classes of “Lipids” Understand the nomenclature and the physical properties of fatty acids and the relation of these properties to the saturation state of the fatty acids. Recognize the structure and function of different classes of polar lipids. Recognize the structure’s most popular examples for each class of lipids. Understand the role of lipids as pigments, signals, and cofactors, knowing different examples Classification 1. Storage lipids. 2. Structural lipids in membranes. 3. Lipids as signals, cofactors and pigments. Storage Lipids Fatty acids are hydrocarbon derivatives. -C4 to C36. -Saturation. -Nomenclature. -Physical properties. Triacylglycerols. -Simple vs. complex triglycerides. -Functions: provide stored energy and insulation. Waxes. -Functions: serve as energy stores and water repellents Structural Lipids Types of membrane lipids: 1. Glycerophospholipids: -Phosphatidic acid. 2. Sphingolipids: -Sphingosine. 3. Sterols: -Steroid nucleus. -Functions. Lipids as signals, cofactors and pigments Phosphatidylinositols act as intracellular signals. Eicosanoids carry messages to nearby cells. -Prostaglandins. -Thromboxanes. -Leukotrienes. Steroid hormones carry messages between tissues. Vitamins A. Vitamins D. Vitamins E. Vitamins K. References Chap. 11 of Lehninger  mo ch 2 1 → th a f st T I a ai 5 ey ny f m C a n I e a tt bu U ¥ b f a th rb y b nd c bo ( re th a ur → on. u b e n y a ra an 1 n o ' c nd t 2 d n th ( n g id ds e → ve ey d hy g s r sa s ry → t a dr o ro o u u 16 s → u h t p p t iw , ra av u be s he o 08 ho p M t e r t c y rt o o e a w ( C ly n d t ar c.T o e ee b f hy a N fa a d n o a dr o ⇒ tt u t n o o re & y n un fa y lt sa sa c c c e a tt y f - c ar A v tu tu a c b a ci ra le h w on r I en d ra te a as tt a t b , t d t y o e ci ( in # w 3 d d a s c xy nu 6 s o h m - a ll a lic be. in r ( ne c do ☆ ) a t ex id 8 n' c t id → tr A s b em el o ha y bo nd ve lon n ) g) d t o v we e cm ry W , I ra E c r f I S e T a £ hy ha ly t tr dr :) ty 0 I ee o c in ↳ t ox & o n o y a ," nf l, I W c : 0 p ig I id % p - s & o e t T ] th ur th. si e b a y i t o t l s e n io s d n a. s m & sa 0 id e o e I p me 0 s b po S a en si id in, b t e di ng en e d I in S # g n an a n o d t # so - a s :*. ( p.j p hy bo o -⇔ ro si p c nd I a ) T l  Lipids p o la r ⇔ g r ou p c o o lt Defined on the basis of solubility. Lipids: heterogeneous group of in so lu bl e 5 ! ! water-insoluble (hydrophobic) e t I II organic molecules, they are p ol ar gr ou p s chemically diverse compounds but have one feature: water insoluble li p id ☆ 4 1 1 6 I Many distinct chemical species in a “lipid fraction” - Po lar s? # n D & d on 4% - 7 3 3. p ol a r a m p hi p h il ic A m p h ip a th ic n on po la r 9  Functions ex fl tra ui ce d ll ul ar N.w s ↑ The biological functions of lipids are diverse as their chemistry n o n po la r → Lipids perform three biological ☒ A functions: in tr ac el lu la r f lu id I a 's 1. Lipids in form of a bilayer are essential components of biological membranes. 2. Lipids containing hydrocarbon side chains serve as energy stores. 3. Many intra-and intercellular signaling events involve lipid molecules. É i w e A m ph ip a th ic J, I p h o sp ho lip id & ↳ p o la r hy d r o g r ou p f a t ty A y l ↳ 2 no n p o la r hy dr oc ar b o n c h a in s C - H I G 2 n o n p ol ar f a tt y A c y l c h a ng es  Lipid Classification 1. Storage lipids Triglycerides, Waxes and Fatty acids. Fats and oils are stored forms of energy and are Triglycerides derivatives of fatty acids. 2. Structural lipids in membranes Glycerophospholipids, Sphingolipids, Sterols. are major structural elements in biological membranes 3. Lipids as signals, cofactors and pigments. These lipids are present in small quantities but play crucial roles: Phosphatidylinositols, Eicosanoids Prostaglandins. Thromboxanes. Leukotrienes. Steroid hormones carry messages between tissues. Vitamins A and D are hormone precursors. Vitamins E and K are oxidation-reduction Common lipid signaling molecules: lysophosphatidic acid (LPA) cofactors. sphingosine-1-phosphate (S1P) platelet activating factor (PAF) anandami de or arachidonoyl ethanolamine (AEA)  Storage Lipids Fats and oils are derivatives of Fatty acids. Fatty acids (F.A) are carboxylic acids with long hydrocarbon chains ranging from 4-36 carbon atoms 16- and 18-C long are most abundant. Even number of carbons, 16, 18… the odd are also present but rare.  Storage Lipids The hydrocarbon chain can be fully saturated (without double bonds), or with one, two or three double bonds (cis-configuration only) Usually, they are unbranched, some cases have ethyl, hydroxyl, or three-carbon ring as a branch  Nomenclature The nomenclature of these acids is rather complicated. There are at least five systems in use. Here are some of the above in the different systems. 1. The delta system numbers the double bonds from the carboxyl group (the α carbon), specify the chain length and the number of double bonds separated by a colon Palmitic acid is saturated F. A with 16 C atoms ➔ 16:0 Stearic acid ➔ 18:0 2. Whereas the omega system indicates where the first double bond is counting from the other end of the molecule (the methyl group, the ω carbon).  ③ G s p ① S y 4 ol s ig n € y w w ns th u e ) ② a e si ns rm l a s b a li n of o t ng d in n ① ② p d./ r fl s sy m os a / P r m v a e p ta m er in d to m g a y n s la t m P e n io ss d n ed op ( ← in ia u in s m la c R - e r re d to :p rs a I ia se to.t D ) r w g b s lo. od S Jj f y lo n pr. w th os ta P ) e gl la nz an sm y di n a m e t me YU s e mb ls s M 0.I ix I I O I a s I C sa sr Nomenclature - ⇔ m o I m s a eg ts y a Linoleic acid ➔ 18:2( 9,12) 5 b 'd I on N 74 d 2, 0 112 C I 7 (⇒ W H, 2, 14 8 J E G I P ii 8 % ,1.9 's 5 ! o ? 2 m Y # - y Arachodonic acids ➔20:4 ( 5,8,11,14) 87 eg 12 6 I: S 57 D # a 6 is 1 8 ? f R ,d 'i ? u a O F a p & F F " ns ke ea 0 d I s D a. l 0 - , t p W i 13 I 3 I ol. it y p 1= IF t' s t " I E o i I 12 s ly 1 & s ± f ↘ 6 7 " in IN un a I.I s &. s 8 a T JU ↳ s 1.I I it 8 I N 1 t  Omega Fatty acids -Essential F.A Linoleic (18:29,12) w6 Linolenic (18:39,12,15) w3 R e a l p o ly u n sa t. Arachidonic (20:45,8,11,14) w6 R ea l p o ly u n s a t  The position of the double bond should be specified superscript numbers following the  (delta) Oleic acid ➔ 18:1( 9) Linoleic acid ➔ 18:2( 9,12) Linolenic acid ➔ 18:3( 9,12,15) The location of double bonds is 9=10; 12=13; 15=16 Arachodonic acids ➔20:4 ( 5,8,11,14) The polyunsaturated F. A is never conjugated, the double bond is separated by a methyl group 1 9  f : co nj u ga te I s # ◦ ⇐ (d oub & p le- o sin , ly u gle n -d sa oub tu le. it ra.) te d E fa - tt s y.a a.a id re R hy ea ne dr l v o c a er rb on c w on Polyunsaturated F. A i ju ↳ ga & te d Double bonds are not conjugated, why? d. ou b le Arachodonic acids ➔20:4 ( 5,8,11,14) b o nd s E  4 g D ↳ ↔ ly ia & c c on er fi o g cy lg e u l m st r a o 4 er t ly io H n no if O ce a ic o c r a a f cy t h ol l p io n a g ol a fa ¥ C ri t t H ly ty I ce ni 2 a a tz c ro l id 0 H ph ↳ ↳ P os ph O A a H ti d T ic r De : & ia c ph a.- y p lg h os c ly ph os c id 1 p h oly er ra p o j o ly l i (( tio ra n t ti.I & on - 21 T * ' d H , ia I 1% " cy i # 1) lg.a ' ly a c 4 Ade a n er o d ol ld - posit 's ⅓ e w ③ m cy 5 i ~ on JI to 03 Th o ird d fa pl a % 3 a ph tt sm 1 fa os p y & tty t h a "½ 0 a c ac t id 1 id o e & I 4 a '# 6 i " 1 & j f if # t e & I ½ O b ☆ R I. y  u ns a s v f tu at a r s tt y a ur te at a d ed a c m id ph ip. e a S ↳ D 7 st th o ic L % lu ou er b i F & if il g bl e ic p it o.a # a bo I , hy nd ti o - & dr s t n p op i SL la ho s ki W b ← n a (c I sm ph I ic ⇔ d t on a os it ju m y of er ph ol ; & ga em s ± & -a so ip lu tio. br id h g b n) e 2 - il an e 8 s it 3 a y if & y of (= D t 3 ' u d ⇔ ) M es ra # s -a a ti '- a bo TI tu on t ra nd $ G ⇐ s. - tio n f /b a so t P 2 on tt a o n ( y la o I f ds il s r n P & T.a ro om S a & h o of.c £ te c bo ic ha m 3 li. id 0 nd in = d 9 s p H li ol in g l 25 8 y s Jf % t D o u fo m e n ns ) rc a ap ( s a es m a o a t # ii b o r c. p el tu.I l ☆ p t: tt m a ho i p fr ra sp i - rb n y- e el e.W o 1 - d e tin se u ft ha ti , id 4/ z g m p dy 1 liq o in l st I 1 - a 5 of 12 f p o re ui P et 0 C d in o.s lc w 1 t '⇔ f j oh 1 o ol ) 2 is f g I 5 & s e i ly G p @ I sa m ! c h o : J os 1 N tu.P si er p 25 ra o.F h m l o 4 te → ti 2 & d.w II p d et 4 h ic ti s 4 I µ N ee o n o F. s " d la r g a a.p li d I ! n. ☆. s  so lu b il So J it lu o y b b il it , g y D 9 D es J e # sa at tu ur ra a t tio io n. n :.: → I ⇔ t I N.: - 4 1 2 m.P ↓ G sg R.T l iq a w u w (2 ns at 5 ur w ) at.T 0 ed ☑ # ☆  Double bonds are not conjugated Conjugated double bonds in a molecule, mean that the single and double bonds alternate. These enables the electrons to be delocalised over the whole system and so be shared by many atoms. The electrons may move around the whole system. Resonance structures result from electrons not being fixed in position. In ions, resonance and electron delocalization occurs to "distribute" the charge around. In molecules, resonance and electron delocalization occurs in aromatic rings and conjugated double bonds. Conjugated double bonds are more stable than isolated ones.  Molecular structure Name so lid at RT & F G 12 c g Lauric acid: saturated C12 M. P - 4 9 Myristic acid: saturated C14 MJ.I T M mp Palmitic acid: saturated C16 -1 $ Stearic acid: saturated C18 M P s t o Oleic acid: monounsaturated C18 m.p t. B O d o u b le b on d.: # f li q a ⇒t R 1.t £ '¾ :* w a i t→ & t o il a , a ', 1 I. 12 s ☆ Linoleic acid: diunsaturated C18 N ' 13 W I T.) f or ce s, w a s m a bb γ-Linolenic acid: triunsaturated C18 M p - 0 Arachidonic acid: tetraunsaturated C20 m ar 5 ↳ ⇔ ,s o 2 5 a J TA m ap I ( R oo m2 5t en a t u ns at II  j → ( ☒ W j ) L ur 8 & I y T u.A 1, st. s I ✓ a 'I ☑ s, ½ j at m L a s I.P a T so lid m M f. ¼ D I & oeb -P m a i. m e li e s sa ( lt ÷ 6 S =.p l. s ) tu o ) 11 P o w ra lu e as ) m lu tio bi j * b n lit , 7 - ← el G o JA ili u ti a o W i ng ty e il W i h , ns sa jb at s.P di ny 1p 25 % t.F 2 p I ig ⑨ 0.f ②..a '.a 5 & ① g 5 ☆  Longer the fatty acid chain –The higher the melting temperature (i.e. more solid at room temp) More double bonds -lower the melting temperature (i.e. more liquid at room temperature)  Physical properties of fatty acids Physical properties of F. A and the compounds containing them are largely determined by the length and degree of unsaturation of the hydrocarbon chain 1. Solubility: The non-polar hydrocarbon chain accounts for the poor solubility of F. A in water Lauric acid 12:0 M. Wt 200 ➔ sol. In water 0.063 mg/g Glucose M.wt 180 ➔ water sol. Is 1.1mg/g The carboxyl group is polar and this accounts for the slight solubility of short-chain fatty acids in water The longer the fatty acid acyl and fewer the double bonds, the lower the solubility in water 2. Melting points Melting points are strongly influenced by the length and degree of unsaturation at R.T the saturated F. A with length chain 12-24 has waxy consistency while the unsaturated F. A is liquid  Fully saturated molecule ➔ free rotation around each C-C This gives the hydrocarbon chain great freedom and flexibility ➔ adopt the most stable Saturated chains pack conformation which is the tightly and form more rigid, fully extended form in which organized aggregates the steric hindrance of neighboring atoms is minimized The molecules can pack together tightly in nearly crystalline arrays. So the Vander Waal interaction and the hydrophobic interaction are maximized The high thermal energy required to disorder (melt) these highly ordered F.A molecules ➔ higher melting points  In the unsaturated F. A the cis configuration double bond forces a kink (bend) in the hydrocarbon chain Unsaturated chains bend and pack in a less ordered way, with greater potential for motion F.A with one or more kinks cannot pack together as tightly as fully saturated F.A and their interactions are weaker So the unsaturated F.As take less thermal energy to diso