Medical Biochemistry Final | UNE Biochemistry
Final Questions And Answers
In glycolysis, ____ is considered the committed step in the pathway. ✅PFK-1
Phospholipids are made up of one or more fatty acids, a core, a phosphate, and which
one of the following? ✅alcohol
cholesterol has a unique chemical structure with four fused rings that allows it to serve
what critical role in our bodies ✅regulating membrane fluidity
Pyruvate plays a central role in intermediary metabolism. Which three chemical
functional groups does it contain? ✅carboxylic acid, methyl, ketone
The urea cycle takes place in which subcellular location(s)? ✅cytosol, mitochondria
Which pathway below requires the use of NADPH? ✅cholesterol biosynthesis
Individuals with Lesch-Nyhan would be expected to build up which compound due to
their enzyme deficiency? ✅uric acid
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)
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
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)
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
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
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