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Chapter 18 Preparation for the Cycle

Terms in this set (33)

Where does the citric acid cycle take place in the cell?
Mitochondria
The activated carrier of acyl groups is ________________.
Coenzyme A
In the presence of oxygen, pyruvate is converted to ________________.
Acetyl CoA
________________ is a large, multi-subunit enzyme complex that links glycolysis and the citric acid cycle under aerobic conditions.
i) pyruvate dehydrogenase
________________ provides a flexible linker between active sites within the pyruvate dehydrogenase (PDH) complex.
Lipoamide
Pyruvate is decarboxylated at this active site in PDH
E₁
The coenzyme ________________ is the prosthetic group in the decarboxylation of pyruvate.
thiamine pyrophosphate (TPP)
________________: Arsenite inhibits the function of this component of the PDH.
E₃
________________: The type of enzyme regulation process that inhibits the PDH complex.
phosphorylation
________________ is caused by a deficiency in vitamin B1.
BeriBeri
__________________ is the PDH subunit responsible for the regeneration of the oxidized form of lipoamide.
Ans: Dihydrolipoyl dehydrogenase (E3) Section: 18.1
Decarboxylation, oxidation, and __________________ are the three steps critical to preserve the free energy derived from decarboxylation of the PDH complex.
Ans: transfer to CoA Section: 18.1
E1 of the PDH complex requires the coenzyme __________________ for proper activity.
Ans: thiamine pyrophospate Section: 18.1
E2 of the PDH complex contains a lipoyl group that is covalently attached to a __________________ residue of the enzyme.
Ans: lysine Section: 18.1
A __________________ is the critical functional group of lipoamide responsible for carrying acetyl groups and maintaining the free energy of CoA.
Ans: Sulfhydryl (−SH) Section: 18.1
__________________ provides a flexible linkage for substrate to move between active sites on the PDH.
Ans: Lipoamide Section: 18.1
__________________ inserts the lipoamide arm of the Sulfhydryl (− SH) domain deep into the channel in E1.
Ans: E2 Section: 18.1
PDH is inactivated when it the enzyme is __________________.
Ans: phosphorylated Section: 18.2
The high-energy charge which results in increasing concentration of NADH __________________ the activity of PDH.
Ans: inhibits Section: 18.2
A deficiency in the vitamin thiamine causes the disease ____________.
Ans: Beriberi Section: 18.2
The citric acid cycle is also known as the:
A) Krebs cycle.
B) Cori cycle.
C) tricarboxylic acid cycle.
D) A and B.
E) A, B, and C.
A) Krebs cycle.
C) tricarboxylic acid cycle.
Acetyl CoA is:
A) the activated form of acyl groups.
B) formed by citrate synthase.
C) the fuel for the citric acid cycle.
D) A and C.
E) A, B, and C.
D) A and C.
A) the activated form of acyl groups.
C) the fuel for the citric acid cycle.
Pyruvate is decarboxylated by which subunit of the PDH?
A) E1
B) E2
C) E3
D) E4
E) E5
A) E1
Which enzyme(s) is/are responsible for the following reaction?
Pyruvate + CoA + NAD⁺ → Acetyl CoA + NADH + H⁺ + CO2
A) acetyl CoA synthetase
B) pyruvate decarboxylase
C) pyruvate dehydrogenase complex
D) A and B
E) A, B, and C
C) pyruvate dehydrogenase complex
What are the steps involved (in order) in the conversion of pyruvate to acetyl CoA?
A) decarboxylation, oxidation, transfer to CoA
B) decarboxylation, transfer to CoA, oxidation
C) oxidation, decarboxylation, transfer to CoA
D) oxidation, transfer to CoA, decarboxylation
E) None of the above.
A) decarboxylation, oxidation, transfer to CoA
Which of the following vitamins are precursors to coenzymes that are necessary for the formation of acetyl CoA from pyruvate?
A) thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid
B) thiamine, riboflavin, niacin, lipoic acid, pantothenic acid, and biotin
C) thiamine, riboflavin, niacin, and biotin
D) thiamine, riboflavin, and lipoic acid
E) None of the above.
A) thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid
Which of the following functions as a "flexible swinging arm" when it transfers the reaction intermediate from one active site to the next?
A) FAD
B) NAD+
C) lipoamide
D) thiamine pyrophosphate
E) coenzyme A
C) lipoamide
Pyruvate dehydrogenase is _______________ when ATP-ADP ratios are high.
A) activated
B) inhibited
C) phosphorylated
D) B and C
E) A and C
B) inhibited
PDH phosphatase deficiency results in which condition?
A) overstimulated PDH
B) low blood glucose
C) chronic elevated plasma lactate
D) high levels of acetyl CoA
E) None of the above.
C) chronic elevated plasma lactate
Milling and polishing rice results in:
A) the loss of the husk of rice.
B) white rice.
C) the potential for Beriberi.
D) the loss of thiamine pyrophosphase.
E) All of the above.
E) All of the above.
A) the loss of the husk of rice.
B) white rice.
C) the potential for Beriberi.
D) the loss of thiamine pyrophosphase.
Beriberi symptoms are similar to those of which disease?
A) arsenite poisoning
B) lactic acidosis
C) Type II diabetes
D) scurvy
E) cancer
A) arsenite poisoning
Which of the following conditions will activate PDH kinase, which catalyzes the phorphorylation and inactivation of E1 in the PDH complex?
A) elevated concentrations of NADH and ATP
B) elevated concentrations of NAD+ and ADP
C) Ca2+
D) insulin
E) elevated concentrations of acetyl CoA
A) elevated concentrations of NADH and ATP
In addition to PDH, what other enzymes are key regulatory sites in the citric acid cycle?
A) isocitrate dehydrogenase
B) alpha-ketoglutarate dehydrogenase
C) citrate synthase (in bacteria)
D) A and B
E) A, B, and C
E) A, B, and C
A) isocitrate dehydrogenase
B) alpha-ketoglutarate dehydrogenase
C) citrate synthase (in bacteria)
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