Exam (elaborations) BIOCHEM CHAPTER 17

BIOCHEM CHAPTER 17 EXAM 17
the 8 enzymes of the citric acid cycle function in a multistep catalytic cycle to oxidize an
acetyl group to 2 CO2 molecules with the concomitant generation of __NADH,
__FADH2, and __GTP.

The free energy released when the reduced coenzyme ultimately reduce O2 is used to
generate ATP - CORRECT ANSWER-the 8 enzymes of the citric acid cycle function in
a multistep catalytic cycle to oxidize an acetyl group to 2 CO2 molecules with the
concomitant generation of 3 NADH, 1 FADH2, and 1 GTP.

The free energy released when the reduced coenzyme ultimately reduce O2 is used to
generate ATP

acetyl groups enter the citric acid cycle as acetyl coA.

the pyruvate dehydrogenase multienzyme complex, which contains __types of enzymes
and __types of coenzymes, generates acetyl-CoA from the glycolytic product pyruvate.

The lipoyllsyl arm of E2 acts as a tether that swings reactive groups between enzymes
in the enzyme. - CORRECT ANSWER-acetyl groups enter the citric acid cycle as acetyl
coA.

the pyruvate dehydrogenase multienzyme complex, which contains 3 types of enzymes
and 5 types of coenzymes, generates acetyl-CoA from the glycolytic product pyruvate.

The lipoyllsyl arm of E2 acts as a tether that swings reactive groups between enzymes
in the enzyme.

________ ________ catalyzes the condensation of acetyl CoA and oxaloacetate in a
highly exergonic reaction - CORRECT ANSWER-citrate synthase catalyzes the
condensation of acetyl CoA and oxaloacetate in a highly exergonic reaction

________ catalyzes the isomerization of citrate to isocitrate, and isocitrate
dehydrogenase catalyzes the oxidative decarboxylationof isocitrate to a-ketoglutarate to
produce the citric acid cycle's first ________ and NADH - CORRECT ANSWER-
aconitase catalyzes the isomerization of citrate to isocitrate, and isocitrate
dehydrogenase catalyzes the oxidative decarboxylationof isocitrate to a-ketoglutarate to
produce the citric acid cycle's first CO2 and NADH

a-ketoglutarate dehydrogenase catalyzes the oxidative decarboxylation of a-
ketoglutarate to produce succinyl-CoA and the citric acid cycle's 2nd CO2 and NADH -
CORRECT ANSWER-a-ketoglutarate dehydrogenase catalyzes the oxidative

,decarboxylation of a-ketoglutarate to produce succinyl-CoA and the citric acid cycle's
2nd CO2 and NADH

________________ synthetase couples the cleavage of succinyl CoA to the synthesis
of GTP with phosphoric-enzyme intermediate - CORRECT ANSWER-succinyl-CoA
synthetase couples the cleavage of succinyl CoA to the synthesis of GTP with
phosphoric-enzyme intermediate

the citric acid cycle's remaining 3 reactions, catalyzed by succinate dehydrogenase,
fumarase, and malate dehydrogenase, regenerate ________ to continue the citric acid
cycle. - CORRECT ANSWER-the citric acid cycle's remaining 3 reactions, catalyzed by
succinate dehydrogenase, fumarase, and malate dehydrogenase, regenerate
oxaloacetate to continue the citric acid cycle.

entry of glucose-derived acetyl CoA into the citric acid cycle is regulated at the pyruvate
dehydrogenase step by ________ ________ (by NADH & acetyl-CoA) and by covalent
modification. - CORRECT ANSWER-entry of glucose-derived acetyl CoA into the citric
acid cycle is regulated at the pyruvate dehydrogenase step by product inhibition (by
NADH & acetyl-CoA) and by covalent modification.

the citric acid cycle itself is ________ at the steps catalyzed by citrate synthase, NAD+-
dependent isocitrate dehydroginase, and a-ketoglutarate dehydrogenase - CORRECT
ANSWER-the citric acid cycle itself is regulated at the steps catalyzed by citrate
synthase, NAD+-dependent isocitrate dehydroginase, and a-ketoglutarate
dehydrogenase

cataplerotic reactions ________ citric acid cycle intermediates. - CORRECT ANSWER-
cataplerotic reactions deplete citric acid cycle intermediates.

________ reactions such as the pyruvate carboxylase reaction replenish citric acid
cycle intermediates. - CORRECT ANSWER-anaplerotic reactions such as the pyruvate
carboxylase reaction replenish citric acid cycle intermediates.

the glyoxylate cycle, which operates only in ________, bacteria, and fungi, requires the
glyoxysomal enzymes isocitrate lyase and malate synthase.

this variation of the citric acid cycle permits net synthesis of ________ from acetyl-CoA -
CORRECT ANSWER-the glyoxylate cycle, which operates only in plants, bacteria, and
fungi, requires the glyoxysomal enzymes isocitrate lyase and malate synthase.

this variation of the citric acid cycle permits net synthesis of glucose from acetyl-CoA

main fuel sources for citric acid cycle:
(1)pyruvate from ________
(2)fatty acids from ________ in mitochondria
(3)amino acids from ________ cycle

, **all broken down to acetyl CoA for oxidation - CORRECT ANSWER-main fuel sources
for citric acid cycle:
(1)pyruvate from glycolysis
(2)fatty acids from oxidation in mitochondria
(3)amino acids from urea cycle

**all broken down to acetyl CoA for oxidation

citric acid cycle =

-8 rxns that oxidize the acetyl group of acetyl CoA into __ molecules of CO2
-produces NADH, FADH2, _____
-cycle is named after the first rxn's product; citrate
-oxaloacetate consumed in the first step is regenerated in the last step - CORRECT
ANSWER-citric acid cycle =

-8 rxns that oxidize the acetyl group of acetyl CoA into 2 molecules of CO2
-produces NADH, FADH2, GTP
-cycle is named after the first rxn's product; citrate
-oxaloacetate consumed in the first step is regenerated in the last step

citric acid cycle, net rxn:

(3NAD+)+(FAD)+(GDP)+(Pi)+(acetyl-CoA) -->
(3NADH)+(FADH2)+(GTP)+(CoA)+(2CO2)

________ _____ = product of pyruvate dehydrogenase rxn

NADH, FADH2 = enters electron transport system

GTP = converted to ATP

CO2 = diffuses out of cell to _____ and Hb - CORRECT ANSWER-citric acid cycle, net
rxn:

(3NAD+)+(FAD)+(GDP)+(Pi)+(acetyl-CoA) -->
(3NADH)+(FADH2)+(GTP)+(CoA)+(2CO2)

acetyl CoA = product of pyruvate dehydrogenase rxn

NADH, FADH2 = enters electron transport system

GTP = converted to ATP

CO2 = diffuses out of cell to RBC and Hb