UNE Biochemistry Final UPDATED
ACTUAL Exam Questions and CORRECT
Answers
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
Which of the following reactions of the urea cycle takes place in the mitochondria? - CORRECT
ANSWER - 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? - CORRECT ANSWER - Arginine
ACTUAL Exam Questions and CORRECT
Answers
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
Which of the following reactions of the urea cycle takes place in the mitochondria? - CORRECT
ANSWER - 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? - CORRECT ANSWER - Arginine
