Fol, B12, SAM

Question 1

What happens at the Pteridine ring of Folate?

Answer 1

Contains the site of oxidation and reduction.

Question 2

Sulfa drugs are an analog of what structure of Folate?

Answer 2

Para-aminobenzoic acid (PABA)

Question 3

Most of the Folate in the body is reduced to what form?

Answer 3

FH4 - tetrahydrofolate

Question 4

Dihydrofolate is oxidized or reduced to Tetrahydrofolate?

Answer 4

Oxidized

Question 5

Damage to the intestinal mucosa, such as in Crohn’s, Alcoholism, and Celiac disease, can cause an inhibition of absorption of what substance?

Answer 5

Folate

Question 6

What is the most oxidized form of FH4?

Answer 6

N10-formyl-FH4

Question 7

What is the most reduced form of FH4?

Answer 7

N5-methyl-FH4

Question 8

When FH4 is trapped as N5-methyl-FH4 and cannot be oxidized, it can cause what type of deficiency?

Answer 8

Functional folate deficiency

Question 9

What is the major source of carbon for the one carbon pool?

Answer 9

Serine, from dietary carbs as 3-phosphoglycerate

Question 10

FH4 is needed for what type of base synthesis?

Answer 10

Purine synthesis (ultimately DNA synthesis)

Question 11

The cancer drug 5-fluorouracil targets this reaction.

Answer 11

The production of dTMP from dUMP via N5N10-methylene-FH4

Question 12

The cancer drug Methotrexate targets what reaction?

Answer 12

The rxn of dihydrofolate reductase

Converts FH2 to FH4

Question 13

B12 has two forms in the body, what are they?

Answer 13

Methylcobalamin and 5’-deoxyadenosylcobalamin

Question 14

Vitmain B12 contains what metal?

Answer 14

Cobalt

Question 15

Homocysteine is converted to what, via B12 and Folate?

Answer 15

Methionine

Question 16

The conversion of Methylmalonyl-CoA to Succinyl-CoA requires what?

Answer 16

Vitamin B12

Question 17

Vegans may develop a B12 deficiency many years after starting their diet. Why is this?

Answer 17

B12 is absorbed in the liver and stored there in excess.

Question 18

Pernicious Anemia is caused by a deficiency in what?

Answer 18

Intrinsic Factor

Question 19

This substance is secreted by gastric parietal cells, binds to B12 for transport in the intestinal tract, and complexes with transcobalamin II before entering circulation

Answer 19

Intrinsic Factor

Question 20

During a Schilling test, this substance is labeled in measured in different stages to determine a deficiency in what other substance?

Answer 20

Cobalt is labeled to test for B12 deficiency.

Question 21

The conversion of Homocysteine to Methionine requires what?

Answer 21

B12 (and folate)

Question 22

Folate adds one carbon groups to what type of atoms?

Answer 22

carbon or sulfur atoms

Question 23

SAM adds methyl groups to what type of atoms?

Answer 23

nitrogen or oxygen atoms

Question 24

SAM is made from what 2 substances?

Answer 24

Methionine and ATP

Question 25

SAM is a precursor to what substance?

Answer 25

Homocysteine

Question 26

B12 is trapped in the methylated form when deficient in what?

Answer 26

Homocysteine

Question 27

This process occurs in the liver and is an alternative pathway for the conversion of Homocysteine to Methionine

Answer 27

Choline –> Betaine, which methylates the sulfur atom of homocysteine

Question 28

Folate deficiency in pregnant women will eventually show an elevation in what?

Answer 28

Homocysteine

Question 29

This folate deficiency is caused by decreased synthesis in Thymine and Purine bases. This shows large RBC’s that do not function properly.

Answer 29

Megaloblastic Anemia

Question 30

An alcoholic can suffer from Megaloblastic anemia due to Folate or B12. Name a test which can differentiate between the two deficiencies.

Answer 30

Measure:
Homocysteine for Folate/B12 deficiency
Methylmalonyl-CoA for B12 deficiency **only one definitive for B12 and rules out Folate

Question 31

Schilling test shows that a patient is unable to absorb crystalline B12, what is the deficiency?

Answer 31

Low activity of pepsin, which causes the B12 to remain bound to R-binders and not intrinsic factor