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42 Cards in this Set
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A,D,E,K
vitamin class |
fat soluble vitamins
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characteristics of folic acid
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water sol
cofactor for enzymes in aa and nucleotide metabolism neural tube defects |
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active form of folic acid
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THF
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folic acid that can't return to THF without help
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5-methyl-THF
requires B12 and reductase (MTHFR) |
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source of carbon for metylation reactions
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serine
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THF metabolism gets what byproducts
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5 methyl THF for homocysteine met
N10 formyl THF for purine synth converts dUMP to dTMP for DNA for R & WBCs (on the way back to DHF) |
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hallmark of folate def anemia
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macrocytic (b/c low DNA), normochromic
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end product of Homocysteine metab
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methionine
for methylation rxns nec for SAM |
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end product of methionine metab
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homocysteine
methionine to SAM to SAH to homcysteine and adenosine- H causes problems (need B12 & folate to rid) |
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vitamines required for homocysteine removal
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folate & B12 (cobalamine)
or B6 |
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cobalamine is what vit
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B12
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enzyme for homocysteine removal with folate & B12
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methionine synthatase
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pathways using SAM
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(all produce homocysteine)
NE to epi guanidinoacetate to creatine nucleotides to methylated Ntds Phosphatidylethanolamine to phosphatidylcholine acetylserotonin to melatonin |
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pathways for removing homocysteine
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folate &B12- methionine synthatase- to methionine
transsulfuration pathway- cystathionine synthase & B6- cystathionine to cysteine |
2
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baby w/dislocated eye lens, osteoporosis, MR, spontanous blood clots
Dies in 20s w/heart dz |
cystathionine synthase def
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toxic effects of elevated homocysteine
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pre-eclampsia (I risk factor)
endo damage oxidation of chol modification apolipos plt adhes & aggregat savenge NO (vasoconstriction) |
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source for folate
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green leafies, fruit & liver
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primary cause of folate deficiency
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dietary intake
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secondary causes of folate deficiency
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malabsorp (duod)
alch leukemia & chemo anticonvulsants dialysis premature |
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dietary requirements for folate
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have ~ 3mo supply in body
mostly in liver need ~ 100-200 micrograms/day increased need during pregnancy |
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uptake/absorption of folate
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polyglutamate forms in food
hydroxylase at brush border decreases to 1 (can't go past 1) monoglutamate form into entero convert to THF & 5 met THF THF used in cell MethylTHF into blood w/binding protein |
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methylenetetrahydrofolate reductase gives...
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THF from 5 met THF
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deficiency in methylentetrahydrofolate gives...
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big risk for pre-eclampsia
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assessment of folate levels
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need RBC folate concentration
(serum levels not reliable- variable with intake) |
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stages of folate deficiency
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1- serum levels fall
2- serum & RBC levels low 3- defective EPOesis 4- clinical def= macrocytic, hypochromic anemia |
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source of B12
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only in animal products
(produced by bacteria in animals) stored in human for 5-10 years recycled in liver |
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reactions involving B12
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methionine synthetase (clear homocysteine)
methylmalonyl CoA mutase |
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deficiency in B12 causes
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megaloblastic anemia AND neurological deficit
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corrin ring
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structure of B12
cobalt in center (cyanocobalamine is supplement) |
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R proteins
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glycoprotein (from mucus cell)
in saliva for cobalamine digestion need acid to remove B12 from food |
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Intrinsic Factor necessary for
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B12 absorption
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TC II
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transcobalamine II
takes B12 to tissues (from ileum) marker for B12 activity (only avail when nec) |
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B12 is absorbed at...
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only terminal ileum, with IF
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increased homocysteine AND increased methylmalonic acid
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B12 deficiency
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increased homocysteine levels only
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folate deficiency
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form of B12 in blood
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methylcobalamine
(for clearing homocysteine) |
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form of B12 in tissues
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adenosylcobalamine
(for clearing branched aas & odd chain FAs - go to succinyl CoA) |
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methylmalonyl CoA mutase
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requires ado-B12
clears branched chain aas (methionine, valine, isoleucine) & odd-chain FAs gives succinyl CoA |
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causes of B12 def
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strict veg diet
achlorhydia (low stom acid) panc insuff pernicious anemia Ab to IF TC II defect |
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lack of IF causes
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pernicious anemia
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dx of pernicious anemia
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Schillings test
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Schillings test
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dx pernicious anemia
saturate tissues w/B12 radiolabeled B12 24 hr urine to check % cleared <10% = pernicious anemia |
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