Chapter 21: Citric Acid Cycle Matching Choose the correct answer from the list. Not all the answers will be used. A) B) C) D) E) F) G) !) $) %) K) &)
oxaloacetate malate synthase malate malonate Krebs cycle aconitase succinylCo CoA synthetase α"eto#lutarate carbon dioxide malate de dehydro#enase isocitrate succinate de dehydro#enase
'. Another Another name name for the citri citricc acid cycle cycle is the ((((((. ((((((. Ans E &e*el of Difficulty Easy +ection Chapter 21 Introduction
,. (((((( is is the first first com-ound com-ound that is is oxidied oxidied in the the citric citric acid cycle. cycle. Ans K &e*el of Difficulty /oderate +ection 21-1. Cycle Overview 0 21-3. Enzye! o" the Citric Acid Cycle
1. (((((( is is an enyme enyme that cataly catalyes es a substrate substratele*e le*ell -hos-horyl -hos-horylation. ation. Ans G &e*el of Difficulty /oderate +ection 21-3. Enzye! o" the Citric Acid Cycle
2. 3he citric citric acid cycle cycle intermedia intermediate te (((((( is found at the the be#innin# be#innin# and at the the end of the citric acid cycle.
Ans A &e*el of Difficulty Easy +ection 21-1. Cycle Overview
4. 3he only membranebound enyme of the citric acid cycle is ((((((. Ans & &e*el of Difficulty Easy +ection 21-1. Cycle Overview# 21-3. Enzye! o" the Citric Acid Cycle
5. 3he name of this citric acid cycle intermediate0 ((((((0 is deri*ed from 6a--le.7 Ans C &e*el of Difficulty Easy +ection 21-1. Cycle Overview
8. 3he enyme (((((( contains an iron−sulfur cluster. Ans F &e*el of Difficulty /oderate +ection 21-3. Enzye! o" the Citric Acid Cycle
9. 3he com-ound (((((( is a com-etiti*e inhibitor of succinate dehydro#enase. Ans D &e*el of Difficulty /oderate +ection 21-3. Enzye! o" the Citric Acid Cycle
Multiple Choice :. ;hich of the followin# coenymes is re
thiamine -yro-hos-hate li-oic acid FAD NAD> biotin
Ans A &e*el of Difficulty /oderate +ection 21-2. Meta$olic %ource! o" Acetyl-Coenzye A '?. E, of the -yru*ate dehydro#enase com-lex contains a li-oyl #rou- that is co*alently attached to a (((((( residue of the enyme= A) B) C) D) E)
#lutamate serine lysine ar#inine histidine
Ans C &e*el of Difficulty /oderate +ection 21-2. Meta$olic %ource! o" Acetyl-Coenzye A ''. ;hich of the followin# is an intermediate between citrate and isocitrate in the citric acid cycle= A) B) C) D) E)
hydroxyethyl3@@ carboxybiotin oxalosuccinate succinyl-hos-hate cisaconitate
Ans E &e*el of Difficulty Easy +ection 21-1. Cycle Overview ',. ;hich of the followin# is the metabolic intermediate that condenses with oxaloacetate to form citrate= A) B) C) D) E)
acetylCoA carboxybiotin oxalosuccinate succinyl-hos-hate cisaconitate
Ans A &e*el of Difficulty Easy +ection 21-1. Cycle Overview '1. Durin# the oxidation of isocitrate0 the intermediate that is decarboxylated to form α "eto#lutarate is ((((((. A)
hydroxyethyl3@@
B) C) D) E)
carboxybiotin oxalosuccinate succinyl-hos-hate cisaconitate
Ans C &e*el of Difficulty Difficult +ection 21-3. Enzye! o" the Citric Acid Cycle '2. ;hich of the followin# enymes of the citric acid cycle contains an FAD -rosthetic #rou-= A) B) C) D) E)
isocitrate dehydro#enase α"eto#lutarate dehydro#enase succinylCoA synthetase succinate dehydro#enase malate dehydro#enase
Ans D &e*el of Difficulty Easy +ection 21-3. Enzye! o" the Citric Acid Cycle '4. $n which of the followin# locations do eu"aryotes house the enymes of the citric acid cycle= A) B) C) D) E)
cytosol mitochondrial matrix endo-lasmic reticulum Gol#i a--aratus outer mitochondrial membrane
Ans B &e*el of Difficulty Easy +ection 21-1. Cycle Overview '5. !ow many NAD! are -roduced when one acetyl #rou- is oxidied in the citric acid cycle= A) B) C) D) E)
' , 1 2 more than 2
Ans C &e*el of Difficulty Easy +ection 21-1. Cycle Overview
'8. ;hich of the followin# terms describes the citric acid cycle is referred to as bein# both catabolic and anabolic= A) B) C) D)
am-hibolic am-hi-athic ana-lerotic cata-lerotic
Ans A &e*el of Difficulty Easy +ection Chapter 21 Introduction 0 21-&. 'he Aphi$olic (ature o" the Citric Acid Cycle '9. 3he reaction that is catalyed by -yru*ate carboxylase is an exam-le of an (((((( reaction because it re-lenishes the citric acid cycle intermediates that ha*e been si-honed off for biosynthesis. A) B) C) D)
am-hibolic am-hi-athic ana-lerotic cata-lerotic
Ans C &e*el of Difficulty Easy +ection 21-&. 'he Aphi$olic (ature o" the Citric Acid Cycle
':. ;hich of these com-ounds is oxidied by a multienyme com-lex that re
,C
C
C
C ,
!
A)
A
B)
A ,C
C!, C
CA ,
A!
C)
A ,C
C!, C!
CA , A
D)
A ,C
C!, C!, C
CA ,
E)
C!1 C
+CoA
Ans D &e*el of Difficulty /oderate +ection 21-2. Meta$olic %ource! o" Acetyl-Coenzye A ,?. 3he isomeriation of citrate to isocitrate A) is the only unnecessary ste- of the citric acid cycle. B) -rotects cells from the toxic effects of arsenite ion. C) con*erts a tertiary alcohol0 which cannot easily be oxidied0 to a secondary alcohol that can be oxidied. D) is a maor re#ulatory ste- for the citric acid cycle. E) is an oxidation reaction. Ans C &e*el of Difficulty Difficult +ection 21-3. Enzye! o" the Citric Acid Cycle ,'. ;hich of the followin# is correct concernin# the metabolic reaction shown below= )yruvate * (A+* * CoA-%,
Acetyl-CoA * (A+, * ,* * CO2
A) 3he enyme that catalyes this reaction contains a -yridoxal -hos-hate -rosthetic #rou-. B) 3his reaction is sometimes referred to as an ana-lerotic reaction in that it 6refills7 the citric acid cycle when intermediates ha*e been remo*ed for biosynthesis. C) 3he enyme that catalyes this metabolic con*ersion is acti*ated by hi#h concentrations of A3@. D) 3his reaction is an oxidati*e decarboxylation. E) 3his reaction is catalyed by an enyme in the cytosol of the cell. Ans D &e*el of Difficulty /oderate +ection 21-2. Meta$olic %ource! o" Acetyl-Coenzye A ,,. ;hich of the followin# causes -yru*ate dehydro#enase "inase to catalye the -hos-horylation and inacti*ation of E' in the -yru*ate dehydro#enase com-lex= A) B) C) D) E)
ele*ated concentrations of NAD! and A3@ ele*ated concentrations of NAD> and AD@ Ca,> insulin ele*ated concentrations of acetylCoA
Ans A &e*el of Difficulty Difficult +ection 21-. egulation o" the Citric Acid Cycle ,1. $f acetylCoA labeled with '2C0 as shown in the fi#ure to the ri#ht0 were used as the substrate for the citric acid cycle0 which of the followin# intermediates would be -roduced durin# the first round of the cycle=
CoA+
C
A! ! A ,C
A)
C
C
C!, CA ,
!
CA ,
! ! ,C
B)
C!, C ,
C
C
!
C ,
A! ! A ,C
C)
C!, CA ,
C
C
!
CA ,
! ! ,C C !
D)
C
C!, C ,
C ,
A! ! A ,C
E)
C C !
C!, CA ,
CA ,
Ans B &e*el of Difficulty Difficult +ection 21-1. Cycle Overview ,2. ;hich of the followin# ser*es as a 6swin#in# arm7 when it transfers a reaction intermediate from one acti*e site to the next= A) B) C) D) E) Ans C
FAD NAD> &i-oamide 3hiamine -yro-hos-hate Coenyme A
C! 1
&e*el of Difficulty /oderate +ection 21-2. Meta$olic %ource! o" Acetyl-Coenzye A
,4. ;hich of the followin# best describes the citric acid cycle as a central -athway of metabolism= A) $t is im-ortant for reco*ery of ener#y from carbohydrates only. B) $t is im-ortant for reco*ery of ener#y from fatty acids only. C) $t is im-ortant for reco*ery of ener#y from amino acids only. D) $t is im-ortant for reco*ery of ener#y from se*eral metabolic fuels that are bro"en down to acetylCoA. E) nly A) and B) abo*e Ans D &e*el of Difficulty Easy +ection 21-1. Cycle Overview ,5. ;hich of the followin# coenymes is N3 used by the -yru*ate dehydro#enase com-lex= A) B) C) D) E)
thiamine -yro-hos-hate -yridoxal -hos-hate coenenyme A FAD NAD>
Ans B &e*el of Difficulty /oderate +ection 21-2. Meta$olic %ource! o" Acetyl-Coenzye A ,8. ;hich of the followin# enymes catalyes a reaction with the -ictured com-ound as an intermediate= A) B) C) D) E)
"eto#lutarate dehydro#enase succinylCoA synthetase succinate dehydro#enase fumarase malate dehydro#enase
COO-
α
CH2 CH2
C 2 -
OP
Ans B &e*el of Difficulty /oderate +ection 21-3. Enzye! o" the Citric Acid Cycle ,9. ;hich of the followin# can be said about the isocitrate -roduct of aconitase= A)
3he -roduct always has the confi#uration.
O
B) C) D)
3he -roduct always has the + confi#uration. 3he -roduct can ha*e either the or + confi#uration 3he -roduct isnt chiral0 so has neither confi#uration
Ans A &e*el of Difficulty Difficult +ection 21-3. Enzye! o" the Citric Acid Cycle ,:. ;hich of the followin# enymes of the citric acid cycle is inhibited by A3@= A) B) C) D) E)
citrate synthase isocitrate dehydro#enase α"eto#lutarate dehydro#enase succinylCoA synthetase malate dehydro#enase
Ans B &e*el of Difficulty Difficult +ection 21-. egulation o" the Citric Acid Cycle OH
1?. ;hich enyme has an intermediate of the form -resented= 3@@ thiamine -yro-hos-hate) A) B) C) D) E)
enolase aldolase -yru*ate decarboxylase #lyceraldehyde1-hos-hate dehydro#enase lactate dehydro#enase
H3C
C
TPP
Ans C &e*el of Difficulty Difficult +ection 21-2. Meta$olic %ource! o" Acetyl-Coenzye A
1'. ;hich of the followin# amino acids -artici-ates in the transfer of a -hos-hate #rou- in the reaction catalyed by succinylCoA synthetase= A) B) C) D) E)
as-artate #lutamate histidine lysine serine
Ans C &e*el of Difficulty Difficult +ection 21-3. Enzye! o" the Citric Acid Cycle
1,. ;hich enyme has an intermediate of the form -resented= A) B) C) D) E)
citrate synthase aconitase isocitrate dehydro#enase succinylCoA synthetase succinate dehydro#enase
O-
O C
C H2 C
C OO -
HC C OO -
Ans B &e*el of Difficulty /oderate +ection 21-3. Enzye! o" the Citric Acid Cycle
11. !ow many electrons are transferred from one acetyl #rou- when it is con*erted to two carbon dioxide molecules in the citric acid cycle= A) B) C) D) E)
, 2 5 9 '?
Ans D &e*el of Difficulty Easy +ection 21-. egulation o" the Citric Acid Cycle