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UNE Biochemistry Final, Final Exam Review UNE Medical Biochemistry – Q’s & A’s (Graded A+)
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UNE Biochemistry Final, Final Exam Review UNE Medical Biochemistry – Q’s & A’s (Graded A+)
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UNE Biochemistry Final, Final Exam Review UNEMedical Biochemistry – Q’s & A’s (Graded A+)
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
Ans - 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 Ans -
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 Ans - Increases degradation of HMG-CoA reductase
Dietary cholesterol is primarily transported in the body by which of the
following lipoproteins? Correct Ans - 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 Ans - 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 Ans -
Decreasing hepatic cholesterol biosynthesis
A deficiency in the LDL receptor will result in an initial decrease in which
of the following? Correct Ans - 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
Ans - 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 Ans -
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 Ans - 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 Ans - 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 Ans - Cholesterol ester transfer protein (CETP)
Which of the following is a major source of extracellular cholesterol for
human tissues? Correct Ans - 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 Ans - 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 Ans
- 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 Ans - 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 Ans -
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 Ans - 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 Ans - Homogentisate
oxidase
Methotrexate is a potent anticancer agent that starves dividing cells of
deoxyribonucleotides through direct inhibition of which of the following
processes? Correct Ans - 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 Ans - Elevated uric acid
Which of the following is the common intermediate for purine synthesis?
Correct Ans - 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 Ans - Thioredoxin
, In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be
allosterically activated by which of the following compounds? Correct
Ans - 5-phosphoribosyl 1-pyrophosphate (PRPP)
Which of the following enzymes is used directly in the synthesis of dTMP
(thymidine)? Correct Ans - 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 Ans - 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 Ans - Orotate
phosphoribosyltransferase
The transamination of all amino acids requires which of the following
cofactors? Correct Ans - Pyridoxal phosphate (PLP)
Ubiquitination is a means of targeting a protein for which of the following
cellular processes? Correct Ans - Proteasomal degradation
Which of the following reactions of the urea cycle takes place in the
mitochondria? Correct Ans - 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 Ans - 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?
Correct Ans - Loss of function of cystathionine- β synthase
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