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CASE FILES: BIOCHEMISTRY
In summary,
folate
is a vitamin acquired from the diet that is
essential for
1-carbon metabolism.
Inadequate folate levels inhibit
DNA synthesis
by lim-
iting
purine nucleotide and dTMP levels,
which results in the abnormal cel-
lular proliferation observed in
megaloblastic anemia.
Folate is also required to
replenish the
methionine pool for SAM-dependent methylation reactions.
C O M P R E H E N SIO N Q U E ST IO N S
[4.1]
Because of the close interrelationship between the vitamins, patients
with deficiencies of either folate or vitamin B12 exhibit similar symp-
toms. Which of the following tests would best help distinguish between
a folate and vitamin B12 deficiency?
A. Activity of methionine synthase
B. Blood level of cystathionine
C. Blood level of homocysteine
D. Blood level of methionine
E. Blood level of methylmalonate
For Questions [4.2] to [4.4] refer to the following list of vitamins:
A. Ascorbic acid (vitamin C)
B. Biotin
C. Cobalamin (vitamin B12)
D. Folic acid
E. Niacin (vitamin B3)
F.
Pantothenic acid
G. Riboflavin (vitamin B2)
H. Thiamine (vitamin B1)
For each patient, described in the Questions [4.2] to [4.4], select the
vitamin that is most likely to be deficient.
[4.2]
A muscular 25-year-old male presents with dermatitis and an inflamed
tongue. A history reveals that he has been consuming raw eggs as part
of his training regimen for the past 6 months.
[4.3]
A 30-year-old male goes to his dentist complaining of loosening teeth.
Examination also reveals his gums are swollen, purple, and spongy. The
dentist also notes that the patient’s fingers have multiple splinter hem-
orrhages near the distal ends of the nail and that a wound on the
patient’s forearm has failed to heal properly.
[4.4]
A female neonate is found to have a small spina bifida in her lower
spinal column that could affect bladder and lower limb function.
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