UNE BIOCHEMISTRY COMPREHENSIVE QUESTIONS AND VERIFIED ANSWERS
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
,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
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? - ☑️☑️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? - ☑️☑️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? - ☑️☑️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? - ☑️☑️Cholesterol ester
transfer protein (CETP)
Which of the following is a major source of extracellular cholesterol for human tissues? -
☑️☑️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?
- ☑️☑️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? - ☑️☑️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? - ☑️☑️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? - ☑️☑️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? -
☑️☑️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? - ☑️☑️Homogentisate oxidase
Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides
through direct inhibition of which of the following processes? - ☑️☑️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? - ☑️☑️Elevated uric acid
Which of the following is the common intermediate for purine synthesis? - ☑️☑️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? -
☑️☑️Thioredoxin
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)
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
,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
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? - ☑️☑️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? - ☑️☑️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? - ☑️☑️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? - ☑️☑️Cholesterol ester
transfer protein (CETP)
Which of the following is a major source of extracellular cholesterol for human tissues? -
☑️☑️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?
- ☑️☑️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? - ☑️☑️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? - ☑️☑️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? - ☑️☑️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? -
☑️☑️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? - ☑️☑️Homogentisate oxidase
Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides
through direct inhibition of which of the following processes? - ☑️☑️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? - ☑️☑️Elevated uric acid
Which of the following is the common intermediate for purine synthesis? - ☑️☑️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? -
☑️☑️Thioredoxin
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)
