Cobalamin Flashcards
Vitamin ______
consits of
synthetic form is present in ______
Has ____ attached to cobalt
B12
corrin ring, w 4 pyrroles w Co at center
supplements, fortified food
cyanide
Found in
highest conc
not present in
_____ must be supplemented
animal products (meat, dairy, eggs)
clams, liver
plants
strict vegetarians/vegans
synthesized solely via
in animals, GI fermentation
B12 is released by
released from
combines w
microorganisms
supports growth of b12 synth microorganisms, vitamin is absorbed/incorporated into animal tissues
HCl in stomach
protein complexes in stomach, duodenum, jejunum
salivary glycoproteins (haptocorrins) protecting B12 from chemical denaturing in stomach
Parietal cells secrete
In intestines, haptocorrin is
IF cobalamin complex then goes to
eventually stored in
glycoprotein called IF
digested via pancreatic tryspin and B12 transferred to IF
terminal ileum, absorb by ileal receptors
liver
B12 is a ____ in rxns for
Adenosylcobalamin required for
Methylcobalamin required for
w/out b12
____ also occurs with folate def
_____ buildup only occurs w
Test ____ for identifying B12 def
cofactor, biosynth of A, metabolic intermediates, purines, nucleotides
conversion of methylmalonyl CoA to succinyl CoA
conversion of homocysteine to methionine
rxns dont proceed normall, precursors build up
homocysteine
MMA
MMA
Def caused by
less common for
vegans become
other causes
malabsorption by IF def (PA, gastrectomy) or disease of distal ileum (Celiac, ileitis, IBD)
dec intake- liver stores lots of B12
deficient over years
Atrophic gastritis, bariatric surgery
Pernicious anemia
Gastric biopsy reveals
over time
Lack of IF
AI disorder w production of autoantibodies against IF/parietal cell antigens
infiltrate of lymphocytes/plasma cells in LP
mucosa atrophies, dec sec of HCl/IF
B12 not absorbed
Def can cause sx of
indiv usually
detected by
CM
Bilateral PN via
Neuro manifestations includ
megaloblastic (macrocytic) anemia
asx
inc MCV
anemia, glossitis, angular cheilosis
demyelination of Posterior/pyramidal tracts of spinal cord
paresthesias, muscle weakness, difficulty walking, dementia, psychosis
Lab abnormality
Peripheral smear indicates
may be before
reticulocytes are
MCV >100, leukopenia/thrombocytopenia
hypersegmented PMN
anemia
low (dec RBC production)
Diagnostic testing via
if borderline/inconclusive
Toxicity
B12 level
test for MMA/homocysteine
No adverse effects
