Biochemistry C784: Module 4 Exam
Questions & Answers Guide
A 45-year-old man has a mild heart attack and a history of vascular disease. He is placed
on a Mediterranean diet and statin drug therapy. Which of the following will be the most
likely result of this drug therapy?
Low blood LDLs
In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically
activated by which of the following compounds?
5-phosphoribosyl 1-pyrophosphate (PRPP)
Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)?
Thymidylate synthase
The regulation of PRPP synthetase is critical in the production of both purines and
pyrimidines. This enzyme is inhibited under which of the following conditions?
When both GDP and ADP are elevated
A 4-year-old girl presented to the clinic with megaloblastic anemia and failure to thrive.
Urinalysis showed significant sediment with extremely high levels of orotic acid. A
deficiency in which of the following enzymes would be consistent with this presentation?
Orotate phosphoribosyltransferase
The transamination of all amino acids requires which of the following cofactors?
Pyridoxal phosphate (PLP)
Ubiquitination is a means of targeting a protein for which of the following cellular
processes?
Proteasomal degradation
Which of the following reactions of the urea cycle takes place in the mitochondria?
The synthesis of carbamoyl phosphate
Several amino acids are intermediates of the urea cycle, having side ammonia groups that
join with free carbon dioxide (CO2) and ammonia to produce net excretion of ammonia as
urea. Which of the following amino acids has a nitrogen in its side chain and is an
intermediate of the urea cycle?
Arginine
Homocystinuria can be caused by several different enzyme or vitamin deficiencies. An
elevation of homocysteine and a decrease in cysteine would most likely present due to
which of the following deficiencies?
Loss of function of cystathionine-β synthase
In an individual with a deficiency in the branched chain ketoacid dehydrogenase complex,
metabolism of which of the following amino acids would not likely be impaired?
Tyrosine
S-adenosylmethionine (SAM) is synthesized from ATP and methionine. A deficiency in
which of the following enzymes would impair the production of SAM?
Methionine adenosyltransferase (MAT)
The conversion of ribose bases into deoxy-bases will be occurring under which of the
following conditions?
When cells are proliferating
,A patient recently diagnosed with colon cancer is being treated with 5-fluorouracil. Which
of the following enzymes will this drug directly inhibit?
Thymidylate synthase
An elevation of purine nucleotides will negatively regulate pyrimidine synthesis through
which of the following mechanisms?
Inhibiting the activity of carbamoyl phosphate synthetase II
Purine biosynthesis starts with the activation of a 5-carbon sugar. In this initial reaction,
ribose 5-phosphate is converted into which of the following compounds?
PRPP (5- phosphoribosylpyrophosphate)
A 40-year-old male comes in to the doctor's office with severe pain in his big toe. He is
diagnosed with gout. Allopurinol is administered and this drug will inhibit which of the
following enzymes?
Xanthine oxidase
In the salvage of purines, hypoxanthine-guanine phosphoribosyl transferase (HGPRT) is
responsible for which of the following processes?
Conversion of guanine to guanosine monophosphate (GMP)
In the case of a deficiency of biotin, which of the following enzymes required for fatty acid
metabolism will be impaired?
Acetyl-CoA carboxylase
During fatty acid synthesis, after the initial step involving acetyl-CoA, the fatty acid chain
is elongated by the addition of which of the following compounds?
Malonyl-CoA
Which of the following compounds or substrates is required for the synthesis of tyrosine?
(+ indicates the compound is required; - indicates the compound is not required)
4
A 2-day-old infant test positive for hyperphenylalaninemia. This is most likely caused by a
heritable defect in which of the following enzymes?
Phenylalanine hydroxylase
You and a friend are being chased by a bear. Under these conditions levels of epinephrine
are increased due to metabolism of which of the following amino acids?
Tyrosine
In pyrimidine synthesis, uridine triphosphate (UTP) can feedback and inhibit which of the
following enzymes?
Carbamoyl phosphate synthase II
Which of the following characteristics distinguish most RNA molecules from DNA?
Uridine base on RNA, whereas a thymidine base on DNA
Which of the following lipoproteins distributes dietary lipids?
Chylomicron
The interaction fo chylomicrons with lipoprotein lipase is stimulated by which of the
following App proteins?
ApoCII
Nascent chylomicrons are synthesized in which tissue?
Intestine
Bile salts are synthesized from cholesterol and are used for the emulsification of dietary
lipids. What is the primary fate of bile salts during digestion?
They are reabsorbed in the ileum
,The glucose-alanine cycle is a method of transferring ammonia from the skeletal muscle to
the liver. In this process the non-toxic carrier of ammonia is which of the following
compounds?
Alanine
Which of the following enzymes is correctly paired with its activator?
N-acetylglutamate synthatase; arginine
The urea cycle takes place in which of the following subcellular locations?
the cytosol and the mitochondria
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)?
CPS I
Which of the following enzymes is the regulatory step in the urea cycle?
Carbamoyl phosphate synthetase I (CPS I)
Which of the following statements is consistent with nitrogen transport in the fasted state?
The urea cycle will be active
A comatose infant is brought to the ER. In the course of the examination, plasma ammonia
was found to be elevated 20-fold over normal values. Urine orotic acid and uracil were both
greater than normal. A defect of which of the following enzymes is the most likely
diagnosis?
Ornithine transcarbamoylase
Your patient presents with a deficiency of the enzyme that catalyzes synthesis of N-
acetylglutamate (NAGs). Which of the following would be a consequence of this deficiency
in the patient?
Increased amino acids in the blood
The cellular uptake of LDL increases intracellular cholesterol levels. This has which of the
following impacts on de novo cholesterol synthesis?
Increases degradation of HMG-CoA reductase
Dietary cholesterol is primarily transported in the body by which of the following
lipoproteins?
Chylomicron
Secondary bile salts are generated by bacterial modification of primary bile salts in the
intestinal lumen. These modifications have which of the following impacts on bile salt
solubility?
Decrease solubility
A 47-year-old male is prescribed a statin (HMG-CoA reductase inhibitor) to manage his
elevated LDL cholesterol. What is the initial mechanism of action for obtaining the desired
effect in this man?
Decreasing hepatic cholesterol biosynthesis
A deficiency in the LDL receptor will result in an initial decrease in which of the following?
Intracellular cholesterol
Nascent chylomicrons interact with HDL particles and obtain which fo the following Apo
proteins?
ApoCII and ApoE
The activity of pancreatic lipase is inhibited by which of the following compounds?
Bile salts
, Which fo the following statements regarding liid digestion and absorption is true?
A. The products of lipid digestion travel in the circulatory system in the form of micelles.
B. The products of lipid digestion diffuse into capillaries in the vicinity of the intestinal
epithelium.
C. Pancreatic lipase emulsifies lipids.
D. The products of lipid digestion are resynthesizes into triacylglycerols in the intestinal
epithelial cells.
e. In the absence of bile salts, no digestion of lipids would occur.
The products of lipid digestion are resynthesizes into triacylglycerols in intestinal epithelial cells.
Under fasting conditions, elevated glucagon will activate which of the following enzymes?
Hormone sensitive lipase
VLDL particles are characterized by which of the following apoproteins?
ApoB100
An increase in insulin leads to which of the following metabolic shifts?
Acetyl CoA carboxylase will become dephosphorylated and active.
Biotin is a cofactor required for which of the following enzymes?
A and B (Acetyl CoA carboxylase and Pyruvate carboxylase)
The first step in fatty acid synthesis is the formation of ________ from acetyl CoA and
carbon dioxide.
Malonyl CoA
Insulin increases the activity of all of the following enzymes except
Hormone sensitive lipase
Which fo the following is the regulatory enzyme for fatty acid synthesis?
Acetyl CoA carboxylase
Which fo the following is the regulated step of fatty acid synthesis in eukaryotes?
Carboxylation of acetyl CoA
Under conditions of starvation, all of the following are true except
Malonyl CoA will be elevated
Which of the following proteins is responsible for the transfer of ApoB48 to nascent
chylomicrons before secretion into circulation?
Microsomal transfer protein (MTP)
The process of beta-oxidation generated all of the following compounds except
NADPH
During the fasted state, lipolysis is facilitated by the action of hormone sensitive lipase. This
enzyme requires which of the following post - translational modification for activation?
Phosphorylation
Adiponectin is secreted from adipocytes. One of the primary roles of adiponectin is to
activate the MAPK pathway in skeletal muscle which enhances the activity of which of the
following pathways?
Beta-oxidation
When the process of glucose oxidation is elevated, the acetyl CoA produced will
allosterically activate which of the following enzymes leading to an increase in the
production of oxaloacetate?
Pyruvate carboxylase
The process of ketogenesis refers to the conversion of acetyl CoA to which of the following
compounds?
Questions & Answers Guide
A 45-year-old man has a mild heart attack and a history of vascular disease. He is placed
on a Mediterranean diet and statin drug therapy. Which of the following will be the most
likely result of this drug therapy?
Low blood LDLs
In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically
activated by which of the following compounds?
5-phosphoribosyl 1-pyrophosphate (PRPP)
Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)?
Thymidylate synthase
The regulation of PRPP synthetase is critical in the production of both purines and
pyrimidines. This enzyme is inhibited under which of the following conditions?
When both GDP and ADP are elevated
A 4-year-old girl presented to the clinic with megaloblastic anemia and failure to thrive.
Urinalysis showed significant sediment with extremely high levels of orotic acid. A
deficiency in which of the following enzymes would be consistent with this presentation?
Orotate phosphoribosyltransferase
The transamination of all amino acids requires which of the following cofactors?
Pyridoxal phosphate (PLP)
Ubiquitination is a means of targeting a protein for which of the following cellular
processes?
Proteasomal degradation
Which of the following reactions of the urea cycle takes place in the mitochondria?
The synthesis of carbamoyl phosphate
Several amino acids are intermediates of the urea cycle, having side ammonia groups that
join with free carbon dioxide (CO2) and ammonia to produce net excretion of ammonia as
urea. Which of the following amino acids has a nitrogen in its side chain and is an
intermediate of the urea cycle?
Arginine
Homocystinuria can be caused by several different enzyme or vitamin deficiencies. An
elevation of homocysteine and a decrease in cysteine would most likely present due to
which of the following deficiencies?
Loss of function of cystathionine-β synthase
In an individual with a deficiency in the branched chain ketoacid dehydrogenase complex,
metabolism of which of the following amino acids would not likely be impaired?
Tyrosine
S-adenosylmethionine (SAM) is synthesized from ATP and methionine. A deficiency in
which of the following enzymes would impair the production of SAM?
Methionine adenosyltransferase (MAT)
The conversion of ribose bases into deoxy-bases will be occurring under which of the
following conditions?
When cells are proliferating
,A patient recently diagnosed with colon cancer is being treated with 5-fluorouracil. Which
of the following enzymes will this drug directly inhibit?
Thymidylate synthase
An elevation of purine nucleotides will negatively regulate pyrimidine synthesis through
which of the following mechanisms?
Inhibiting the activity of carbamoyl phosphate synthetase II
Purine biosynthesis starts with the activation of a 5-carbon sugar. In this initial reaction,
ribose 5-phosphate is converted into which of the following compounds?
PRPP (5- phosphoribosylpyrophosphate)
A 40-year-old male comes in to the doctor's office with severe pain in his big toe. He is
diagnosed with gout. Allopurinol is administered and this drug will inhibit which of the
following enzymes?
Xanthine oxidase
In the salvage of purines, hypoxanthine-guanine phosphoribosyl transferase (HGPRT) is
responsible for which of the following processes?
Conversion of guanine to guanosine monophosphate (GMP)
In the case of a deficiency of biotin, which of the following enzymes required for fatty acid
metabolism will be impaired?
Acetyl-CoA carboxylase
During fatty acid synthesis, after the initial step involving acetyl-CoA, the fatty acid chain
is elongated by the addition of which of the following compounds?
Malonyl-CoA
Which of the following compounds or substrates is required for the synthesis of tyrosine?
(+ indicates the compound is required; - indicates the compound is not required)
4
A 2-day-old infant test positive for hyperphenylalaninemia. This is most likely caused by a
heritable defect in which of the following enzymes?
Phenylalanine hydroxylase
You and a friend are being chased by a bear. Under these conditions levels of epinephrine
are increased due to metabolism of which of the following amino acids?
Tyrosine
In pyrimidine synthesis, uridine triphosphate (UTP) can feedback and inhibit which of the
following enzymes?
Carbamoyl phosphate synthase II
Which of the following characteristics distinguish most RNA molecules from DNA?
Uridine base on RNA, whereas a thymidine base on DNA
Which of the following lipoproteins distributes dietary lipids?
Chylomicron
The interaction fo chylomicrons with lipoprotein lipase is stimulated by which of the
following App proteins?
ApoCII
Nascent chylomicrons are synthesized in which tissue?
Intestine
Bile salts are synthesized from cholesterol and are used for the emulsification of dietary
lipids. What is the primary fate of bile salts during digestion?
They are reabsorbed in the ileum
,The glucose-alanine cycle is a method of transferring ammonia from the skeletal muscle to
the liver. In this process the non-toxic carrier of ammonia is which of the following
compounds?
Alanine
Which of the following enzymes is correctly paired with its activator?
N-acetylglutamate synthatase; arginine
The urea cycle takes place in which of the following subcellular locations?
the cytosol and the mitochondria
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)?
CPS I
Which of the following enzymes is the regulatory step in the urea cycle?
Carbamoyl phosphate synthetase I (CPS I)
Which of the following statements is consistent with nitrogen transport in the fasted state?
The urea cycle will be active
A comatose infant is brought to the ER. In the course of the examination, plasma ammonia
was found to be elevated 20-fold over normal values. Urine orotic acid and uracil were both
greater than normal. A defect of which of the following enzymes is the most likely
diagnosis?
Ornithine transcarbamoylase
Your patient presents with a deficiency of the enzyme that catalyzes synthesis of N-
acetylglutamate (NAGs). Which of the following would be a consequence of this deficiency
in the patient?
Increased amino acids in the blood
The cellular uptake of LDL increases intracellular cholesterol levels. This has which of the
following impacts on de novo cholesterol synthesis?
Increases degradation of HMG-CoA reductase
Dietary cholesterol is primarily transported in the body by which of the following
lipoproteins?
Chylomicron
Secondary bile salts are generated by bacterial modification of primary bile salts in the
intestinal lumen. These modifications have which of the following impacts on bile salt
solubility?
Decrease solubility
A 47-year-old male is prescribed a statin (HMG-CoA reductase inhibitor) to manage his
elevated LDL cholesterol. What is the initial mechanism of action for obtaining the desired
effect in this man?
Decreasing hepatic cholesterol biosynthesis
A deficiency in the LDL receptor will result in an initial decrease in which of the following?
Intracellular cholesterol
Nascent chylomicrons interact with HDL particles and obtain which fo the following Apo
proteins?
ApoCII and ApoE
The activity of pancreatic lipase is inhibited by which of the following compounds?
Bile salts
, Which fo the following statements regarding liid digestion and absorption is true?
A. The products of lipid digestion travel in the circulatory system in the form of micelles.
B. The products of lipid digestion diffuse into capillaries in the vicinity of the intestinal
epithelium.
C. Pancreatic lipase emulsifies lipids.
D. The products of lipid digestion are resynthesizes into triacylglycerols in the intestinal
epithelial cells.
e. In the absence of bile salts, no digestion of lipids would occur.
The products of lipid digestion are resynthesizes into triacylglycerols in intestinal epithelial cells.
Under fasting conditions, elevated glucagon will activate which of the following enzymes?
Hormone sensitive lipase
VLDL particles are characterized by which of the following apoproteins?
ApoB100
An increase in insulin leads to which of the following metabolic shifts?
Acetyl CoA carboxylase will become dephosphorylated and active.
Biotin is a cofactor required for which of the following enzymes?
A and B (Acetyl CoA carboxylase and Pyruvate carboxylase)
The first step in fatty acid synthesis is the formation of ________ from acetyl CoA and
carbon dioxide.
Malonyl CoA
Insulin increases the activity of all of the following enzymes except
Hormone sensitive lipase
Which fo the following is the regulatory enzyme for fatty acid synthesis?
Acetyl CoA carboxylase
Which fo the following is the regulated step of fatty acid synthesis in eukaryotes?
Carboxylation of acetyl CoA
Under conditions of starvation, all of the following are true except
Malonyl CoA will be elevated
Which of the following proteins is responsible for the transfer of ApoB48 to nascent
chylomicrons before secretion into circulation?
Microsomal transfer protein (MTP)
The process of beta-oxidation generated all of the following compounds except
NADPH
During the fasted state, lipolysis is facilitated by the action of hormone sensitive lipase. This
enzyme requires which of the following post - translational modification for activation?
Phosphorylation
Adiponectin is secreted from adipocytes. One of the primary roles of adiponectin is to
activate the MAPK pathway in skeletal muscle which enhances the activity of which of the
following pathways?
Beta-oxidation
When the process of glucose oxidation is elevated, the acetyl CoA produced will
allosterically activate which of the following enzymes leading to an increase in the
production of oxaloacetate?
Pyruvate carboxylase
The process of ketogenesis refers to the conversion of acetyl CoA to which of the following
compounds?
