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Chapter 21 Lipid Biosynthesis
Multiple Choice Questions 1. Biosyn Biosynthe thesis sis of of fatty fatty acids acids and and eicosan eicosanoid oidss Pages: 787-78 !ifficulty: 2 "ns: # Which of the following is not required required in the synthesis of fatty acids?
A) B) C) !) #)
Acetyl-CoA Biotin HCO3 – (CO) "alonyl-CoA $A!H
2. Biosyn Biosynthe thesis sis of of fatty fatty acids acids and and eicosan eicosanoid oidss Pages: 787-788 !ifficulty: 2 "ns: B Which of the following is not true true of the reaction %roducing &alonyl-CoA &alonyl-CoA during fatty acid synthesis?
A) B) C) !) #)
't is sti&ulated y citrate 't requires acyl carrier %rotein (AC*) 't requires CO (or icaronate) One &ole of A+* is con,erted to A!* * i for each &alonyl-CoA synthesi.ed +he cofactor is iotin
$. Biosyn Biosynthe thesis sis of of fatty fatty acids acids and and eicosan eicosanoid oidss Pages: 788-7% !ifficulty: $ "ns: ! /0 'f &alonyl-CoA is synthesi.ed fro& CO and unlaeled acetyl-CoA1 and the laeled &alonate is then used for fatty acid synthesis1 the final %roduct (fatty acid) will ha,e radioacti,e caron in2
A) B) C) !) #)
e,ery C e,ery e,en-nu&ered C-ato& e,ery odd-nu&ered C-ato& no %art of the &olecule only the o&ega-caron ato& (farthest caron fro& C-/)
&. Biosyn Biosynthe thesis sis of of fatty fatty acids acids and and eicosan eicosanoid oidss Page: 7% !ifficulty: 2 "ns: # Which one of the following state&ents est a%%lies to synthesis of fatty acids in E. coli etracts? coli etracts?
A) B) C) !)
Acyl inter&ediates are thioesters of a low &olecular weight %rotein called acyl carrier %rotein CO or HCO3 – is essential 4educing equi,alents are %ro,ided y $A!*H +he ulti&ate source of all the caron ato&s in the fatty acid %roduct is acetyl-CoA
2&8
Chapter 21 Lipid Biosynthesis
#) All of the ao,e are true '. Biosynthesis of fatty acids and eicosanoids Pages: 7&-7' !ifficulty: 2 "ns: ! 'n co&%aring fatty acid iosynthesis with β oidation of fatty acids1 which of the following state&ents is incorrect ?
A) A thioester deri,ati,e of crotonic acid ( trans--utenoic acid) is an inter&ediate in the synthetic %ath1 ut not in the degradati,e %ath B) A thioester deri,ati,e of !- β-hydroyutyrate is an inter&ediate in the synthetic %ath1 not in the degradati,e %ath C) 5atty acid iosynthesis uses $A!*H eclusi,ely1 whereas β oidation uses $A! eclusi,ely
!) 5atty acid degradation is cataly.ed y cytosolic en.y&es6 fatty acid synthesis y &itochondrial en.y&es #) +he condensation of two &oles of acetyl-CoA in the %resence of a crude etract is &ore ra%id in icaronate uffer than in %hos%hate uffer at the sa&e %H6 the clea,age of acetoacetyl-CoA %roceeds equally well in either uffer (. Biosynthesis of fatty acids and eicosanoids Page: 7& !ifficulty: 2 "ns: ! #n.y&es that cataly.e the synthesis of long chain fatty acids in ,erterate cells2
A) B) C) !) #)
act as se,en se%arate %roteins are encoded in &itochondrial genes are locali.ed in the &itochondrial &atri are %art of a single %oly%e%tide chain containing se,eral distinct en.y&e acti,ities ha,e none of the characteristics ao,e
7. Biosynthesis of fatty acids and eicosanoids Page: 7' !ifficulty: 2 "ns: # Which of the following is not true of the fatty acid synthase and the fatty acid β-oidation syste&s?
A) B) C) !) #)
A deri,ati,e of the ,ita&in %antothenic acid is in,ol,ed Acyl-CoA deri,ati,es are inter&ediates !oule onds are oidi.ed or reduced y %yridine nucleotide coen.y&es +he %rocesses occur in different cellular co&%art&ents +he %rocesses occur in the &itochondrial &atri
8. Biosynthesis of fatty acids and eicosanoids Pages: 7'-7( !ifficulty: 2 "ns: ! +he rate-li&iting ste% in fatty acid synthesis is2
A) B) C) !) #)
condensation of acetyl-CoA and &alonyl-CoA for&ation of acetyl-CoA fro& acetate for&ation of &alonyl-CoA fro& &alonate and coen.y&e A the reaction cataly.ed y acetyl-CoA caroylase the reduction of the acetoacetyl grou% to a β-hydroyutyryl grou%
Chapter 21 Lipid Biosynthesis
. Biosynthesis of fatty acids and eicosanoids Page: 77 !ifficulty: 2 "ns: # Which of the following is not true of the fatty acid elongation syste& of ,erterate cells?
A) B) C) !) #)
't in,ol,es the sa&e four-ste% sequence seen in the fatty acid synthase co&%le 't is located in the s&ooth endo%las&ic reticulu& 't %roduces stearoyl-CoA y the etension of %al&itoyl-CoA 't uses &alonyl-CoA as a sustrate +he i&&ediate %recursor of the added carons is acetyl-CoA
1%. Biosynthesis of fatty acids and eicosanoids Page: 77 !ifficulty: 2 "ns: " Which of these can e synthesi.ed y %lants ut not y hu&ans?
A) B) C) !) #)
7inoleate 8/92( ∆:1/ ); *al&itate (/tearate (/92=)
11. Biosynthesis of fatty acids and eicosanoids Page: 78 !ifficulty: $ "ns: B +he en.y&e syste& for adding doule onds to saturated fatty acids requires all of the following except:
A) B) C) !) #)
a &ied-function oidase A+* cytochro&e b &olecular oygen (O ) $A!*H
12. Biosynthesis of fatty acids and eicosanoids Pages: 8%%-8%1 !ifficulty: $ "ns: " Which of these state&ents aout eicosanoid synthesis is true?
A) B) C) !) #)
An early ste% in the %ath to thro&oanes is loc@ed y iu%rofen Arachidonate is deri,ed &ainly y hydrolysis of triacylglycerols As%irin acts y loc@ing the synthesis of arachidonate *lants can synthesi.e leu@otrienes1 ut hu&ans cannot +hro&oanes are %roduced fro& arachidonate ,ia the linear %ath
2&
2'%
Chapter 21 Lipid Biosynthesis
1$. Biosynthesis of triacylglycerols Page: 8%& !ifficulty: 2 "ns: B +he iosynthesis of triacylglycerols fro& acetate occurs &ainly in2
A) B) C) !) #)
ani&als ut not in %lants hu&ans after ingestion of ecess carohydrate hu&ans with low carohydrate inta@e %lants ut not in ani&als none of the ao,e
1&. Biosynthesis of triacylglycerols Page: 8%' !ifficulty: 2 "ns: ! +he synthesis of oth glycero%hos%holi%ids and triacylglycerols in,ol,es2
A) B) C) !) #)
C!*-choline C!*-diacylglycerol %hos%hatidate %hos%hatase %hos%hatidic acid %hos%hoethanola&ine
1'. Biosynthesis of triacylglycerols Page: 8%( !ifficulty: 2 "ns: B Which of these state&ents aout triacylglycerol synthesis is correct?
A) B) C) !) #)
Hu&ans can store &ore energy in glycogen than in triacylglycerols 'nsulin sti&ulates con,ersion of dietary carohydrate into triacylglycerols 't is not a hor&one-sensiti,e %rocess "a&&als are unale to con,ert carohydrates into triacylglycerols *hos%hatidate is not on the %athway of triacylglycerol synthesis
1(. Biosynthesis of )e)*rane phospholipids Pages: 8%8-81$ !ifficulty: 2 "ns: C A strategy that is not e&%loyed in the synthesis of %hos%holi%ids is2
A) B) C) !) #)
condensation of C!*-alcohol with diacylglycerol condensation of C!*-diacylglycerol with alcohol condensation of C!*-diacylglycerol with C!*-alcohol echange of free alcohol with head grou% alcohol of %hos%holi%id re&odeling of head grou% alcohols y che&ical &odification
17. Biosynthesis of )e)*rane phospholipids Pages: 81%-811 !ifficulty: 2 "ns: # All glycerol-containing %hos%holi%ids are synthesi.ed fro&2
A) cardioli%in B) cera&ide
Chapter 21 Lipid Biosynthesis
C) gangliosides !) &e,alonate #) %hos%hatidic acid 18. Biosynthesis of )e)*rane phospholipids Page: 811 !ifficulty: 2 "ns: # 'n E. coli the synthesis of %hos%hatidylethanola&ine directly in,ol,es2
A) B) C) !) #)
acyl carrier %rotein iotin C!*-choline %hos%hatidylglycerol serine
1. Biosynthesis of )e)*rane phospholipids Page: 812 !ifficulty: 2 "ns: ! 'n the synthesis of %hos%hatidylcholine fro& %hos%hatidylethanola&ine1 the ðyl grou% donor is2
A) B) C) !) #)
a tetrahydrofolate deri,ati,e choline ðanol S -adenosylðionine (ado"et) serine
2%. Biosynthesis of )e)*rane phospholipids Page: 81$ !ifficulty: 1 "ns: ! *al&itoyl-CoA1 1 is a direct %recursor of2
A) B) C) !) #)
cholesterol &alonyl-CoA &e,alonate s%hingosine squalene
21. Biosynthesis of )e)*rane phospholipids Page: 81$ !ifficulty: $ "ns: # C!*-diglyceride is not in,ol,ed in the iosynthesis of2
A) B) C) !) #)
%hos%hatidylcholine %hos%hatidylethanola&ine %hos%hatidylglycerol %hos%hatidylserine s%hingo&yelin
22. Biosynthesis of )e)*rane phospholipids Page: 81' !ifficulty: 2 "ns: C Which of the following is true of s%hingoli%id synthesis?
A) All of the caron ato&s of %al&itate and serine are incor%orated into s%hingosine
2'1
2'2
Chapter 21 Lipid Biosynthesis
B) C) !) #)
C!*-s%hingosine is the acti,ated inter&ediate CO is %roduced during the synthesis of cera&ide fro& %al&itate and serine lucose how the first reduction reaction1 with any required cofactors "ns: β-@etoacyl-AC* $A!*H H → β−hydroyacyl-AC* $A!* (>ee 5ig /-1 % G9:) $2. Biosynthesis of fatty acids and eicosanoids Pages: 7%-71 !ifficulty: 2 5atty acid synthesis and fatty acid rea@down occur y si&ilar %athways !escrie1 ,ery riefly1 four ways in which the synthetic and rea@down %athways differ "ns: 5atty acid synthesis (in any order) ( /) e&%loys $A!*H as reducing agent6 () in,ol,es an acyl grou% ound to a %rotein1 AC*6 ( 3) ta@es %lace in the cytosol of ani&als6 (0) in,ol,es the condensation of &alonyl- and acetyl-grou%s6 () in,ol,es the for&ation of the !- β-hydroyacyl deri,ati,e 5atty acid rea@down (/) e&%loys $A! as electron acce%tor6 () in,ol,es acyl grou%s
ound to coen.y&e A6 (3) occurs in the &itochondrial &atri6 (0) does not in,ol,e &alonylderi,ati,es6 () in,ol,es the 7-stereoiso&er of the β-hydroyacyl deri,ati,e $$. Biosynthesis of fatty acids and eicosanoids Pages: 7%-71 !ifficulty: 2 +he synthesis of fatty acids and their rea@down y β oidation occur y se%arate %athways Co&%are the two %aths y filling in the lan@s elow (>o&e lan@s &ay require &ore than one answer)
Acti,ating grou% #lectron carrier coen.y&e(s) Basic units added or re&o,ed Cellular location of %rocess
β oidation >ynthesis IIIIIIIIIIIIIII IIIIIIIIIIIIII IIIIIIIIIIIIIII IIIIIIIIIIIIII IIIIIIIIIIIIIII IIIIIIIIIIIIII IIIIIIIIIIIIIII IIIIIIIIIIIIII
"ns:
β oidation >ynthesis Acti,ating grou%
acyl carrier %rotein
#lectron carrier coen.y&e(s) Basic units added or re&o,ed Cellular location of %rocess
$A!*H &alonyl- and acetylcytosol in ani&als1 chloro%last in %lants
CoA>H $A! acetyl&itochondrial &atri
$&. Biosynthesis of fatty acids and eicosanoids Page: 72 !ifficulty: $ >how the structure of each inter&ediate in the con,ersion of β-hydroyutyryl-AC* to utyryl-AC*
Chapter 21 Lipid Biosynthesis
2''
y the fatty acid synthetase co&%le >how where cofactors %artici%ate 'n your first inter&ediate1 circle the caron ato&s that are deri,ed fro& &alonyl-CoA "ns: β-hydroyutyryl-AC* is first dehydrated1 yielding trans-∆-utenoyl-AC*1 which is then reduced to utyryl-AC*1 with $A!*H as the reducing agent (>ee 5ig /-1 % G:) $'. Biosynthesis of fatty acids and eicosanoids Pages: 7&-7( !ifficulty: $ !escrie the &echanis& for &o,ing acetyl-CoA %roduced in the &itochondrial &atri into the cytosol for fatty acid synthesis "ns: Acetyl-CoA in the &itochondrial &atri condenses with oaloacetate to for& citrate in a reaction cataly.ed y citrate synthase Citrate &o,es out of the &atri ,ia the citrate trans%orter Citrate in the cytosol is clea,ed y citrate lyase1 yielding acetyl-CoA and oaloacetate +o co&%lete the cycle1 oaloacetate in the cytosol is reduced to &alate1 which &o,es into the &itochondrial &atri on the &alate- α-@etoglutarate trans%orter1 and is con,erted to oaloacetate in the &atri $(. Biosynthesis of fatty acids and eicosanoids Page: 8%% !ifficulty: 2 #%lain riefly why we require fats in our diets "ns: !ietary fats %ro,ide the linoleate and linolenate that we need (for eicosanoid synthesis) ut cannot synthesi.e $7. Biosynthesis of fatty acids and eicosanoids Page: 8%1 !ifficulty: $ >@etch the %athway fro& arachidonate to thro&oanes and e%lain how as%irin loc@s the synthesis of thro&oanes "ns: (>ee 5ig /-/1 % 9=/) $8. Biosynthesis of )e)*rane phospholipids Page: 8% !ifficulty: 2 !escrie two asic strategies for acti,ating %recursors in the iosynthesis of %hos%holi%ids "ns: (/) Acti,ate the head grou% y attach&ent to C!*1 as in C!*-choline1 then dis%lace C"* with the hydroyl grou% of glycerol in diacylglycerol () Acti,ate diacylglycerol y the attach&ent of C!*1 then dis%lace C"* with the hydroyl grou% of the head grou%
$. Biosynthesis of )e)*rane phospholipids Pages: 81%-812 !ifficulty: 2 >how the iosynthetic %ath(s) fro& %hos%hatidic acid to %hos%hatidylcholine Jou &ay use shorthand notation for %hos%hatidic acid1 ut na&e any cofactors required in the %ath and show where they are in,ol,ed "ns: *hos%hatidic acid condenses with C+* to for& C!*-diacylglycerol6 then serine dis%laces C"*1 yielding %hos%hatidylserine !ecaroylation of %hos%hatidylserine yields %hos%hatidylethanola&ine1 and ðylation of the a&ino grou% of %hos%hatidylethanola&ine with three ðyl grou%s1 each donated y S -adenosylðionine1 yields %hos%hatidylcholine (>ee 5igs
2'(
Chapter 21 Lipid Biosynthesis
/-1 %9/=1 and 5ig /-G1 % 9/) 'n an alternati,e %ath1 %hos%hocholine condenses with C+*1 for&ing C!*-choline6 %hos%hatidic acid is de%hos%horylated to yield diacylglycerol6 and diacylglycerol dis%laces C"* fro& C!*-choline1 for&ing %hos%hatidylcholine (>ee 5ig /-ee 5ig /-301 % 9/G) &$. Biosynthesis of cholesterol+ steroids+ and isoprenoids Page: 817 !ifficulty: 2 >how the %athway fro& &e,alonate to diðylallyl %yro%hos%hate1 indicating where any cofactors %artici%ate "ns: (>ee 5ig /-31 % 9/G) &&. Biosynthesis of cholesterol+ steroids+ and isoprenoids Page: 817 !ifficulty: $ +he synthesis of cholesterol egins with the condensation of a four-caron unit fro& IIIIIIIIIIIIIII with the two carons of acetyl-CoA to for& a si-caron deri,ati,e i,e its structure1 and circle the ato&s that originated in the acetyl-CoA "ns: Acetoacetyl-CoA6 +he si-caron %roduct is β-hydroy- β-ðylglutaryl-CoA (H"-CoA) (+he structure and carons originating in acetyl-CoA are shown in 5ig /-301 % 9/G) &'. Biosynthesis of cholesterol+ steroids+ and isoprenoids Page: 818 !ifficulty: 2 !escrie the for&ation of farnesyl %yro%hos%hate fro& acti,ated iso%renyl units "ns: +his is the reaction in which diðylallyl %yro%hos%hate condenses head-to-tail with iso%entenyl %yro%hos%hate1 with the eli&ination of ** i (>ee 5ig /-3
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