MEDICAL BIOCHEMISTRY FINAL, UNE
BIOCHEMISTRY FINAL, UNE
BIOCHEMISTRY FINAL, FINAL, FINAL
EXAM REVIEW UNE MEDICAL
BIOCHEMISTRY QUESTIONS AND
ANSWERS
In glycolysis, ____ is considered the committed step in the pathway. - answer PFK-1
Phospholipids are made up of one or more fatty acids, a core, a phosphate, and which one of
the following? - answer alcohol
cholesterol has a unique chemical structure with four fused rings that allows it to serve what
critical role in our bodies - answer regulating membrane fluidity
Pyruvate plays a central role in intermediary metabolism. Which three chemical functional
groups does it contain? - answer carboxylic acid, methyl, ketone
The urea cycle takes place in which subcellular location(s)? - answer cytosol, mitochondria
Which pathway below requires the use of NADPH? - answer cholesterol biosynthesis
Individuals with Lesch-Nyhan would be expected to build up which compound due to their
enzyme deficiency? - answer uric acid
The urea cycle takes place in which of the following subcellular locations? - answer the cytosol
and the mitochondria
,Which of the following enzymes is regulated by N-acetylglutamate (NAGs)? - answer CPS I
Which of the following enzymes is the regulatory step in the urea cycle? - answer Carbamoyl
phosphate synthetase I (CPS I)
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? - 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? - 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? - answer Increases degradation of HMG-
CoA reductase
Dietary cholesterol is primarily transported in the body by which of the following lipoproteins? -
answer Chylomicron
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? - answer Decreasing hepatic cholesterol biosynthesis
A deficiency in the LDL receptor will result in an initial decrease in which of the following? -
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? - 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? - 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? - 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? -
answer Lecithin cholesterol acyltransferase (LCAT)
Which of the following is a major source of extracellular cholesterol for human tissues? - 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? -
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? - 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? - 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? - 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? - 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? - answer Homogentisate oxidase
Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides
through direct inhibition of which of the following processes? - 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? - answer Elevated uric acid
Which of the following is the common intermediate for purine synthesis? - answer Inosine
monophosphate
In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically activated
by which of the following compounds? - answer 5-phosphoribosyl 1-pyrophosphate (PRPP)
Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)? - answer
Thymidylate synthase
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