UNE Biochemistry Final
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? -
correct answer Alanine
Which of the following enzymes is correctly paired with its activator? - correct answer N-
acetylglutamate synthatase; arginine
The urea cycle takes place in which of the following subcellular locations? - correct answer the
cytosol and the mitochondria
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)? - correct answer
CPS I
Which of the following enzymes is the regulatory step in the urea cycle? - correct answer
Carbamoyl phosphate synthetase I (CPS I)
Which of the following statements is consistent with nitrogen transport in the fasted state? -
correct answer 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? - correct
answer 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? - correct answer 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? - correct answer Increases degradation of
HMG-CoA reductase
Dietary cholesterol is primarily transported in the body by which of the following lipoproteins? -
correct answer 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? - correct answer 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? - correct answer Decreasing hepatic cholesterol biosynthesis
A deficiency in the LDL receptor will result in an initial decrease in which of the following? -
correct answer Intracellular cholesterol
,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? - correct answer Low blood LDLs
A 45-year-old man is found to have an elevated serum triglycerides of > 730mg/dL. He tells you
he forgot to fast before his visit and he ate a full breakfast of bacon and eggs before the labs
were drawn. Which of the following lipoproteins would be the largest contributors to a
measurement of plasma triglycerides in this situation? - correct answer Chylomicrons and
VLDLs
In the reaction catalyzed by cholesterol ester transfer protein (CETP), the VLDL particle receives
which of the following compounds from HDL particles? - correct answer Cholesterol-ester
In reverse cholesterol transport HDL interacts with the ABCA1 transporter to move cholesterol
from the cell to the HDL. This also requires the activity of which of the following enzyme? -
correct answer Lecithin cholesterol acyltransferase (LCAT)
HDL particles interact with VLDL particles to exchange cholesterol ester for triacylglyerols.
Which of the following enzymes is responsible for this process? - correct answer Cholesterol
ester transfer protein (CETP)
Which of the following is a major source of extracellular cholesterol for human tissues? -
correct answer LDLs
An individual is suspected of having a deficiency in branched chain keto acid dehydrogenase.
Supplementation of which of the following vitamins or cofactors may help resolve this issue? -
correct answer Thiamine
A 55-year old man presents to his primary care physician with bouts of dizziness and confusion.
He is diagnosed with hyperhomocysteinemia due to a deficiency of cystathionine-ß synthase. In
this individual which of the following amino acids could potentially become essential? - correct
answer Cysteine
Phenylketonuria can be caused by an enzymatic deficiency or it can present due to a deficiency
in which of the following required metabolic cofactors? - correct answer Tetrahydrobiopterin
(BH4)
A 17-year old female presents to her primary care and is diagnosed with a Vitamin B12
(cobalamin) deficiency. In this individual, which of the following reactions would be
compromised? - correct answer Conversion of methyl malonyl-Co A to succinyl-CoA
A 15-year-old female presents to her pediatrician with concerns over her inability to sleep,
increased feelings of depression and generalized fatigue. A full laboratory work-up is ordered
and based on these findings she is diagnosed with a melatonin deficiency. Based on this
information, metabolism of which of the following amino acids is likely impaired? - correct
answer Tryptophan
, A 52-year- old male sought medical help complaining about progressive appearance of
hyperchromic (hyper pigmented) papules on the edge of the second finger of both hands. He
also complained about darkening of urine. Incisional biopsy of one of the spots on his hands
and urine sample tested positive for or homogentisic acid. Based on these findings a diagnosis
of alkaptonuria is made. This diagnosis is consistent with a deficiency in which of the following
enzymes? - correct answer Homogentisate oxidase
Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides
through direct inhibition of which of the following processes? - correct answer Metabolism of
folic acid
A 47-year-old man complains of pain in the joints of his left big toe, which are obviously swollen
and tender. The pain has been chronic but became intolerable the day after Thanksgiving when
he had a large meal and several glasses of red wine. Based on this information a diagnosis of
gout is made. Which of the following is involved in the pathophysiology of this patient's
condition? - correct answer Elevated uric acid
Which of the following is the common intermediate for purine synthesis? - correct answer
Inosine monophosphate
The ribonucleotide reductase is important for converting ribose bases to the deoxy form. This
conversion is coupled with the oxidation of which of the following compounds? - correct
answer Thioredoxin
In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically
activated by which of the following compounds? - correct answer 5-phosphoribosyl 1-
pyrophosphate (PRPP)
Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)? - correct
answer 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? - correct answer 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? - correct answer
Orotate phosphoribosyltransferase
The transamination of all amino acids requires which of the following cofactors? - correct
answer Pyridoxal phosphate (PLP)
Ubiquitination is a means of targeting a protein for which of the following cellular processes? -
correct answer Proteasomal degradation
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? -
correct answer Alanine
Which of the following enzymes is correctly paired with its activator? - correct answer N-
acetylglutamate synthatase; arginine
The urea cycle takes place in which of the following subcellular locations? - correct answer the
cytosol and the mitochondria
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)? - correct answer
CPS I
Which of the following enzymes is the regulatory step in the urea cycle? - correct answer
Carbamoyl phosphate synthetase I (CPS I)
Which of the following statements is consistent with nitrogen transport in the fasted state? -
correct answer 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? - correct
answer 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? - correct answer 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? - correct answer Increases degradation of
HMG-CoA reductase
Dietary cholesterol is primarily transported in the body by which of the following lipoproteins? -
correct answer 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? - correct answer 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? - correct answer Decreasing hepatic cholesterol biosynthesis
A deficiency in the LDL receptor will result in an initial decrease in which of the following? -
correct answer Intracellular cholesterol
,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? - correct answer Low blood LDLs
A 45-year-old man is found to have an elevated serum triglycerides of > 730mg/dL. He tells you
he forgot to fast before his visit and he ate a full breakfast of bacon and eggs before the labs
were drawn. Which of the following lipoproteins would be the largest contributors to a
measurement of plasma triglycerides in this situation? - correct answer Chylomicrons and
VLDLs
In the reaction catalyzed by cholesterol ester transfer protein (CETP), the VLDL particle receives
which of the following compounds from HDL particles? - correct answer Cholesterol-ester
In reverse cholesterol transport HDL interacts with the ABCA1 transporter to move cholesterol
from the cell to the HDL. This also requires the activity of which of the following enzyme? -
correct answer Lecithin cholesterol acyltransferase (LCAT)
HDL particles interact with VLDL particles to exchange cholesterol ester for triacylglyerols.
Which of the following enzymes is responsible for this process? - correct answer Cholesterol
ester transfer protein (CETP)
Which of the following is a major source of extracellular cholesterol for human tissues? -
correct answer LDLs
An individual is suspected of having a deficiency in branched chain keto acid dehydrogenase.
Supplementation of which of the following vitamins or cofactors may help resolve this issue? -
correct answer Thiamine
A 55-year old man presents to his primary care physician with bouts of dizziness and confusion.
He is diagnosed with hyperhomocysteinemia due to a deficiency of cystathionine-ß synthase. In
this individual which of the following amino acids could potentially become essential? - correct
answer Cysteine
Phenylketonuria can be caused by an enzymatic deficiency or it can present due to a deficiency
in which of the following required metabolic cofactors? - correct answer Tetrahydrobiopterin
(BH4)
A 17-year old female presents to her primary care and is diagnosed with a Vitamin B12
(cobalamin) deficiency. In this individual, which of the following reactions would be
compromised? - correct answer Conversion of methyl malonyl-Co A to succinyl-CoA
A 15-year-old female presents to her pediatrician with concerns over her inability to sleep,
increased feelings of depression and generalized fatigue. A full laboratory work-up is ordered
and based on these findings she is diagnosed with a melatonin deficiency. Based on this
information, metabolism of which of the following amino acids is likely impaired? - correct
answer Tryptophan
, A 52-year- old male sought medical help complaining about progressive appearance of
hyperchromic (hyper pigmented) papules on the edge of the second finger of both hands. He
also complained about darkening of urine. Incisional biopsy of one of the spots on his hands
and urine sample tested positive for or homogentisic acid. Based on these findings a diagnosis
of alkaptonuria is made. This diagnosis is consistent with a deficiency in which of the following
enzymes? - correct answer Homogentisate oxidase
Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides
through direct inhibition of which of the following processes? - correct answer Metabolism of
folic acid
A 47-year-old man complains of pain in the joints of his left big toe, which are obviously swollen
and tender. The pain has been chronic but became intolerable the day after Thanksgiving when
he had a large meal and several glasses of red wine. Based on this information a diagnosis of
gout is made. Which of the following is involved in the pathophysiology of this patient's
condition? - correct answer Elevated uric acid
Which of the following is the common intermediate for purine synthesis? - correct answer
Inosine monophosphate
The ribonucleotide reductase is important for converting ribose bases to the deoxy form. This
conversion is coupled with the oxidation of which of the following compounds? - correct
answer Thioredoxin
In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically
activated by which of the following compounds? - correct answer 5-phosphoribosyl 1-
pyrophosphate (PRPP)
Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)? - correct
answer 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? - correct answer 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? - correct answer
Orotate phosphoribosyltransferase
The transamination of all amino acids requires which of the following cofactors? - correct
answer Pyridoxal phosphate (PLP)
Ubiquitination is a means of targeting a protein for which of the following cellular processes? -
correct answer Proteasomal degradation
