Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
33 Cards in this Set
- Front
- Back
|
What are folates converted to inside the intestinal lumen?
|
Folic Acid Monoglutamate
|
|
|
How are folates taken up by the enterocytes of the intestinal lumen?
|
They bind to Folate Binding Protein and are entocytized
|
|
|
What happens to folic acid once it is taken up by the enterocytes of the intestinal lumen?
|
It is reduced to DHF, and then to THF. It is then methylated to form N5-methyl-THF before being released into the bloodstream
|
|
|
How do peripheral cells take up Folate
|
Via Folate Binding Protein
|
|
|
What happens to N5-methyl-THF once taken up by peripheral cells?
|
It is converted to THF and glutamate residues are attached to it to help trap it inside the cell.
|
|
|
What enzyme attaches glutamate residues onto THF?
|
Folylpolyglutamate Synthase
|
|
|
How are one carbon groups transported from the cytoplasm into the mitochondria?
|
N5/N10-methylene-THF transfers a 1-carbon group onto glycine and becomes serine. Serine enters the mitochondria and transfers that 1-carbon group onto THF to form N5/N10-methylene THF.
|
|
|
How is methanol metabolized?
|
Methanol is converted to formaldehyde (alcohol dehydrogenase). Formaldehyde is converted to Formic Acid (Formaldehyde Dehydrogenase). Formic Acid is converted to N10-formyl-THF and then C02
|
|
|
If methanol is metabolized to C02, why does methanol poisoning occur?
|
The rate of reaction for Formic Acid to N10-formyl-THF and then to C02 is very slow so Formic Acid builds up leading to acidosis.
|
|
|
What are the 3 treatment options for methanol ingestion?
|
1) Induce emesis (vomiting)
2) Drink/infuse ethanol 3) Fomepizole (inhibitor) |
|
|
What are the two damaging intermediates of Ethylene Glycol metabolism?
|
Glycolate
Oxolate |
|
|
What are their specific damaging effects on the body?
|
Glycolate = Damages Kidney tubules
Oxolate = binds Ca++ causing hypocalcemia, forms Ca-oxolate crystals damaging the kidney |
|
|
What is the major use of one-carbon groups?
|
Purine synthesis
|
|
|
For most methylation reactions, the methyl group on N5-methyl-THF is not sufficiently reactive. What is the more reactive methyl-group donor?
|
S-adenosyl-methionine (SAM)
|
|
|
In general terms, how is SAM made?
|
N5-methyl-THF adds a 1-carbon group to homocysteine to make methionine which is converted to SAM.
|
|
|
What is the enzyme that converts N5-methyl-THF + Homocysteine to Methionine + THF? What is the cofactor?
|
Methionine Synthase
Methylcobalmin |
|
|
Half of the Homocysteine is converted to Methionine. What happens to the other half?
|
Converted to Cystathionine
|
|
|
What is the function of cystathionine?
|
Needed for proper brain function (mechanism unknown)
|
|
|
What is the dietary source of cobalamin?
|
meats and dairy products
|
|
|
What does cobalamin first bind to in the stomach?
|
Haptocorrin
|
|
|
Where is haptocorrin secreted from?
|
Salivary glands and gastric mucosa
|
|
|
What happens to the cobalamin-haptocorrin complex once in the duodenum?
|
They dissociate and cobalamin binds intrinsic factor?
|
|
|
Where is instrinsic factor secrted from?
|
Parietal cells in the stomach
|
|
|
What occurs once the cobalamin-instrinsic factor complex enters the ileum?
|
It is taken up by intestinal cells via cubam.
|
|
|
What happens to the cobalamin-instrisic factor once inside the ileum enterocyte?
|
They dissociate, cobalamin enters a secretory vesicle, binds transcobalamin II and enters the blood stream
|
|
|
Once taken up by peripheral cells, what two enzymes does cobalamin act as a cofactor for?
|
Methionine Synthase
Methylmalonyl-CoA mutase |
|
|
What is pernicious anemia?
|
Insufficient secretion of instrinsic factor leads to inadequate cobalamin uptake
|
|
|
What chemical is coupled with decreased cobalamin uptake?
|
Nitrous Oxide (laughing gas)
|
|
|
SAM is used in the biosynthesis of these three things
|
Creatine, Phopholipids, EpinephrineS
|
|
|
SAM can also be used to methylate these two things
|
Nucleic Acids and Proteins
|
|
|
What is the function of creatine?
|
Gets phosphorylated by ATP to form Phosphocreatine. This then transports energy to myosin filaments. Creatinine is the waste product.
|
|
|
What is Leucovorin?
|
=Folinic Acid = N5-formyl-THF
Can be converted to N5/N10-methenyl-THF. |
|
|
Why is Leucovorin useful?
|
N5/N10-methenyl-THF is part of the general folate pool. Used following antifolate chemodrugs.
|
