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Biochem-SAM/B12/Fol

Biochem-SAM/B12/Folate-WVSOM Class of 2012

QuestionAnswer
what is the basic function of folate and SAM? transfer of one methyl group to another molecule
folate has what molecule on the end? glutamate
can folate be synthesized? no
what enzyme is responsible for reducing and activating folate? dihydrofolate reductase (dhfr)
general process for making folate? ingest->make monoglutamate->FH2->FH4
what molecule most often donates the carbon group to folate? serine
what are the 3 main molecules that rely on folate for their synthesis? purine and dtmp; serine; methylcobalamin
another name for B12? methylcobalamin
what is the most common form of FH4-C? what is its function? N5-methyl-FH4; transfers methyl group to B12
what is the other name for B12? why? what is important about cobalt? cobalamin; because it has cobalt ring; can form carbon bonds
B12 can only be synthesized how? bacteria
what are the 2 metabolites of B12? methyl cobalamin or deoxyadenosylcobalamin
what are the 3 names for the proteins that bind B12 after ingestion? Haptocorrin, Transcobalamin I, or R-binders
what is the process of B12 uptake to liver or tissue? ingest->binds to transcobalamin I->pancreatic enzymes cleave->binds to intrinsic factor->cleave in ileum->transcobalamin II takes to liver or tissue
what are the 2 reactions that require B12 as a cofactor? conversion of homocysteine to methionine; conversion of methylmalonyl-CoA to Succinyl CoA
Conversion of methylmalonyl-CoA to succinyl CoA requires what B12 form? adenosylcobalamin
Conversion of homocysteine to methionine requires what B12 form? methylcobalamin
is methionine an essential amino acid? yes
what is most important function of SAM? to methylate nucleotides (turns them off)
what disease is associated with hyperhomocysteinemia? cardiovascular disease
what are 3 enzymatic causes of hyperhomocysteinemia? Met synthase, MTHFR, and cystathionine synthase mutations
PLP is derived from what vitamin? B6
how can homocysteine levels be reduced? B6, B12, and folate supplements
macrocytic anemia can result from what deficiency? why? B12 and folate; reduced nucleotides leads to less cellular dividing
in addition to macrocytic anemia, what else can occur in B12 deficiency? why? neurological symptoms; need B12 to make methionine to make SAM, which is precursor for neurotransmitters
what is the methyl trap hypothesis? need folate to get methylcobalamin; need B12 to recycle N5-methyl-tetrahydrofolate
pernicious anemia is a decrease in what? intrinsic factor
normal absorption of crystalline B12 means you can not have what? pernicious anemia
why is B12 deficiency seen in the elderly? reduced gastric secretions (IF) and inadequate diet
what explains how B12 affects dna replication? methyl trap hypothsis
Created by: mhassan on 2008-12-13



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