Fol, B12, SAM Flashcards Preview

Biochem Exam 1 > Fol, B12, SAM > Flashcards

Flashcards in Fol, B12, SAM Deck (31)
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1
Q

What happens at the Pteridine ring of Folate?

A

Contains the site of oxidation and reduction.

2
Q

Sulfa drugs are an analog of what structure of Folate?

A

Para-aminobenzoic acid (PABA)

3
Q

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

A

FH4 - tetrahydrofolate

4
Q

Dihydrofolate is oxidized or reduced to Tetrahydrofolate?

A

Oxidized

5
Q

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

A

Folate

6
Q

What is the most oxidized form of FH4?

A

N10-formyl-FH4

7
Q

What is the most reduced form of FH4?

A

N5-methyl-FH4

8
Q

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

A

Functional folate deficiency

9
Q

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

A

Serine, from dietary carbs as 3-phosphoglycerate

10
Q

FH4 is needed for what type of base synthesis?

A

Purine synthesis (ultimately DNA synthesis)

11
Q

The cancer drug 5-fluorouracil targets this reaction.

A

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

12
Q

The cancer drug Methotrexate targets what reaction?

A

The rxn of dihydrofolate reductase

Converts FH2 to FH4

13
Q

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

A

Methylcobalamin and 5’-deoxyadenosylcobalamin

14
Q

Vitmain B12 contains what metal?

A

Cobalt

15
Q

Homocysteine is converted to what, via B12 and Folate?

A

Methionine

16
Q

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

A

Vitamin B12

17
Q

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

A

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

18
Q

Pernicious Anemia is caused by a deficiency in what?

A

Intrinsic Factor

19
Q

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

A

Intrinsic Factor

20
Q

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

A

Cobalt is labeled to test for B12 deficiency.

21
Q

The conversion of Homocysteine to Methionine requires what?

A

B12 (and folate)

22
Q

Folate adds one carbon groups to what type of atoms?

A

carbon or sulfur atoms

23
Q

SAM adds methyl groups to what type of atoms?

A

nitrogen or oxygen atoms

24
Q

SAM is made from what 2 substances?

A

Methionine and ATP

25
Q

SAM is a precursor to what substance?

A

Homocysteine

26
Q

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

A

Homocysteine

27
Q

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

A

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

28
Q

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

A

Homocysteine

29
Q

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

A

Megaloblastic Anemia

30
Q

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

A

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

31
Q

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

A

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