MCB 450 Exam 4 Test Questions with
Answers Already Passed.
High levels of ATP and citrate: - Answer Inhibit glycolysis
Indicate remote gluconeogenesis
Indicate a high energy-well fed state.
Which of the following would be associated with LOW pyruvate dehydrogenase rate? - Answer
High NADH
The hallmarks of acute alcoholism without food intake are acidosis and hypoglycemia. These
metabolic changes are due to the: - Answer Metabolism of ethanol, which prevents the
production of sufficient levels of blood glucose from lactate, glycerol and alanine.
Hormonal activation of cyclic AMP levels will: - Answer Increase the activation of
gluconeogenesis.
Which of the following vitamins are precursors to coenzymes that are necessary for the
formation of acetyl CoA from pyruvate? - Answer Thiamine, riboflavin, niacin, lipoic acid, and
pantothenic acid
In addition to pyruvate dehydrogenase, what other enzyme(s) in the citric acid cycle has a key
thiamine pyrophosphate coenzyme? - Answer α-ketoglutarate dehydrogenase
Why does acetyl CoA, a product of fatty acid catabolism, influence the pyruvate dehydrogenase
complex (PDH), a control point in carbohydrate catabolism? - Answer When fatty acid
breakdown is high, PDH is inhibited by acetyl CoA due to pyruvate kinase activity.
The citric acid cycle is activated in the presence of oxygen (O2), but what is the link between the
citric acid cycle and O2? - Answer A primary product of the citric acid cycle is NADH, the
principle electron donor to the O2, the last electron acceptor in the electron-transport system.
What is(are) the chemical change(s) involved in the conversion of citrate into isocitrate? -
Answer Dehydration followed by hydration
, The direct movement of substrates from one enzyme to the next is called: - Answer Substrate
channeling
A mutation in the active site of succinyl CoA synthetase where His is converted to Lys would
result in which of the following? - Answer Loss of a succinyl phosphate intermediate
What are the steps involved (in order) in the conversion of pyruvate to acetyl CoA? - Answer
Decarboxylation, oxidation, transfer to CoA
Approximately how many ATP or GTP equivalents are produced during one turn of the citric acid
cycle? - Answer 10
Although we study the citric acid cycle as the final stage oxidation of carbon from glucose, an in-
depth look at the cycle shows intermediates entering and leaving the cycle from a number of
metabolic pathways. With all of these demands on the cycle, how does it maintain a minimal
level of oxaloacetate (OAA) to allow the cycle to function? - Answer OAA is synthesized via
pyruvate carboxylase in an anaplerotic reaction that occurs when acetyl CoA is present.
A 1-month-old male showed abnormalities of the nervous system and lactic acidosis. Enzyme
assay for pyruvate dehydrogenase (PDH) activity on extracts of cultured skin fibroblasts showed
5% of normal activity, with a low concentration (1 x 10-4 mM) of thiamine pyrophosphate (TPP),
but 80% of normal activity when the assay contained a high (0.4 mM) concentration of TPP.
Which one of the following statements concerning this patient is most correct? - Answer
Administration of thiamine is expected to reduce his serum lactate concentration and improve
his clinical symptoms.
Which of these compounds is oxidized by a multienzyme complex that requires five different
coenzymes? - Answer Pyruvate
A low level of carbon dioxide labeled with 14C is accidentally released into the atmosphere
surrounding industrial workers as they resume work following the lunch hour. Unknowingly,
they breathe the contaminated air for 1 hour. Which of the following compounds will be
radioactively labeled? - Answer About one third of the carbons of newly synthesized malonyl
CoA.
The β-oxidation of myristyl-CoA (14:0) yields: - Answer 7 acetyl CoA + 6 FADH2 + 6 NADH + 6
H+.
Answers Already Passed.
High levels of ATP and citrate: - Answer Inhibit glycolysis
Indicate remote gluconeogenesis
Indicate a high energy-well fed state.
Which of the following would be associated with LOW pyruvate dehydrogenase rate? - Answer
High NADH
The hallmarks of acute alcoholism without food intake are acidosis and hypoglycemia. These
metabolic changes are due to the: - Answer Metabolism of ethanol, which prevents the
production of sufficient levels of blood glucose from lactate, glycerol and alanine.
Hormonal activation of cyclic AMP levels will: - Answer Increase the activation of
gluconeogenesis.
Which of the following vitamins are precursors to coenzymes that are necessary for the
formation of acetyl CoA from pyruvate? - Answer Thiamine, riboflavin, niacin, lipoic acid, and
pantothenic acid
In addition to pyruvate dehydrogenase, what other enzyme(s) in the citric acid cycle has a key
thiamine pyrophosphate coenzyme? - Answer α-ketoglutarate dehydrogenase
Why does acetyl CoA, a product of fatty acid catabolism, influence the pyruvate dehydrogenase
complex (PDH), a control point in carbohydrate catabolism? - Answer When fatty acid
breakdown is high, PDH is inhibited by acetyl CoA due to pyruvate kinase activity.
The citric acid cycle is activated in the presence of oxygen (O2), but what is the link between the
citric acid cycle and O2? - Answer A primary product of the citric acid cycle is NADH, the
principle electron donor to the O2, the last electron acceptor in the electron-transport system.
What is(are) the chemical change(s) involved in the conversion of citrate into isocitrate? -
Answer Dehydration followed by hydration
, The direct movement of substrates from one enzyme to the next is called: - Answer Substrate
channeling
A mutation in the active site of succinyl CoA synthetase where His is converted to Lys would
result in which of the following? - Answer Loss of a succinyl phosphate intermediate
What are the steps involved (in order) in the conversion of pyruvate to acetyl CoA? - Answer
Decarboxylation, oxidation, transfer to CoA
Approximately how many ATP or GTP equivalents are produced during one turn of the citric acid
cycle? - Answer 10
Although we study the citric acid cycle as the final stage oxidation of carbon from glucose, an in-
depth look at the cycle shows intermediates entering and leaving the cycle from a number of
metabolic pathways. With all of these demands on the cycle, how does it maintain a minimal
level of oxaloacetate (OAA) to allow the cycle to function? - Answer OAA is synthesized via
pyruvate carboxylase in an anaplerotic reaction that occurs when acetyl CoA is present.
A 1-month-old male showed abnormalities of the nervous system and lactic acidosis. Enzyme
assay for pyruvate dehydrogenase (PDH) activity on extracts of cultured skin fibroblasts showed
5% of normal activity, with a low concentration (1 x 10-4 mM) of thiamine pyrophosphate (TPP),
but 80% of normal activity when the assay contained a high (0.4 mM) concentration of TPP.
Which one of the following statements concerning this patient is most correct? - Answer
Administration of thiamine is expected to reduce his serum lactate concentration and improve
his clinical symptoms.
Which of these compounds is oxidized by a multienzyme complex that requires five different
coenzymes? - Answer Pyruvate
A low level of carbon dioxide labeled with 14C is accidentally released into the atmosphere
surrounding industrial workers as they resume work following the lunch hour. Unknowingly,
they breathe the contaminated air for 1 hour. Which of the following compounds will be
radioactively labeled? - Answer About one third of the carbons of newly synthesized malonyl
CoA.
The β-oxidation of myristyl-CoA (14:0) yields: - Answer 7 acetyl CoA + 6 FADH2 + 6 NADH + 6
H+.
