| Question |
Answer |
| 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 |
Biology Lab Midterm
