Biochem - Nutrition (Part 2: Vitamins B9, B12, C, & D) Flashcards

See p. 94-95 in First Aid 2014 Sections include: -Vitamin B9 (folic acid) -Vitamin B12 (cobalamin) -Vitamin C (ascorbic acid) -Vitamin D

1
Q

What is another name for Vitamin B9?

A

Vitamin B9 (folic acid)

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2
Q

To what is Vitamin B9 (folic acid) converted? For what kind of reactions is this a coenzyme?

A

Converted to tetrahydrofolate (THF), a coenzyme for 1-carbon transfer/methylation reactions.

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3
Q

For what process(es) is Vitamin B9 (folic acid) important?

A

Important for the synthesis of nitrogenous bases in DNA and RNA

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4
Q

What is a source of Vitamin B9 (folic acid)? Where is it absorbed?

A

Found in leafy green vegetables. Absorbed in jejunum. Think: “FOLate from FOLiage”

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5
Q

Describe the body’s Vitamin B9 (folic acid) reserve pool and its location.

A

Small reserve pool stored primarily in the liver

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6
Q

What 3 physical/histological signs/symptoms result from Vitamin B9 (folic acid) deficiency? What key sign/symptom is lacking, and what clinical significance does this have?

A

Macrocytic, megaloblastic anemia; hypersegmented polymorphonuclear cells (PMNs); glossitis; no neurologic symptoms (as opposed to vitamin B12 deficiency).

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7
Q

What are 2 lab findings associated with Vitamin B9 (folic acid) deficiency?

A

Labs: Increased homocysteine, normal methylmalonic acid (unlike Vitamin B12, which has increased homocysteine and methylmalonic acid levels)

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8
Q

What is the most common vitamin deficiency in the United States?

A

Vitamin B9 (folic acid)

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9
Q

What are 2 conditions in which Vitamin B9 (folic acid) deficiency is seen?

A

Seen in alcoholism and pregnancy

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10
Q

What are 3 drugs that can cause Vitamin B9 (folic acid) deficiency?

A

Deficiency can be caused by several drugs (e.g., phenytoin, sulfonamides, methotrexate).

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11
Q

Why is supplemental maternal folic acid given early in pregnancy?

A

Supplemental maternal folic acid in early pregnancy decreases risk of neural tube defects

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12
Q

What is the function of Vitamin B12 (cobalamin)?

A

Cofactor for homocysteine methyltransferase (transfers CH3 groups as methylcobalamin) and methylmalonyl-CoA mutase

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13
Q

What 3 physical/histological signs/symptoms result from Vitamin B12 (cobalamin) deficiency?

A

Macrocytic, megaloblastic anemia; hypersegmented PMNs; paresthesias, and subacute combined degeneration (degeneration of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts) due to abnormal myelin

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14
Q

What are 2 lab findings associated with Vitamin B12 (cobalamin) deficiency?

A

Associated within increased serum homocysteine and methylmalonic acid levels.

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15
Q

What are the neurological findings associated with Vitamin B12 (cobalamin) deficiency, and what causes them?

A

Paresthesias, and subacute combined degeneration (degeneration of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts) due to abnormal myelin

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16
Q

What can result from prolonged Vitamin B12 (cobalamin) deficiency?

A

Prolonged deficiency => irreversible nerve damage

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17
Q

What is the source of Vitamin B12 (cobalamin)? What synthesizes it?

A

Found in animal products; Synthesized only by microorganisms

18
Q

Describe the body’s Vitamin B12 (cobalamin) reserve pool and its location.

A

Very large reserve pool (several years) stored primarily in the liver.

19
Q

What are 4 major causes of Vitamin B12 (cobalamin) deficiency? Give at least one example of each.

A

Deficiency is usually caused by (1) insufficient intake (e.g., veganism), (2) malabsorption (e.g., sprue, enteritis, Diphyllobothrium latum), (3) lack of intrinsic factor (pernicious anemia, gastric bypass surgery), or (4) absence of terminal ileum (Crohn disease).

20
Q

What is diagnostic for pernicious anemia?

A

Anti-intrinsic factor antibodies diagnostic for pernicious anemia

21
Q

Draw a diagram depicting how the following are related: (1) Cysteine (2) Homocysteine (3) Methionine (4) SAM (5) B6 (6) B12 (7) CH3 for anabolic reactions. Include important intermediate/side reactions in the diagram.

A

See p. 94 in First Aid 2014 for visual at bottom left of page

22
Q

Draw a diagram depicting how the following are involved in the metabolism of fatty acids with odd number of C and branched-chain amino acids: (1) B6 (2) B12 (3) Heme (4) Methylmalonyl-CoA (5) Succinyl-CoA. Include important intermediate/side reactions in the diagram.

A

See p. 94 in First Aid 2014 for visual at bottom right of page

23
Q

What is another name for Vitamin B12?

A

Vitamin B12 (cobalamin)

24
Q

What is another name for Vitamin C?

A

Vitamin C (ascorbic acid)

25
Q

What are 4 functions of Vitamin C (ascorbic acid)?

A

(1) Antioxidant. (2) Also facilitates iron absorption by reducing it to Fe2+ state. (3) Necessary for hydroxylation of proline and lysine in collagen synthesis. (4) Necessary for dopamine Beta-hydroxylase, which converts dopamine to NE.

26
Q

What is the source of Vitamin C (ascorbic acid)?

A

Found in fruits and vegetables; Think: Pronounce “ABSORBic” acid.

27
Q

For what condition is Vitamin C (ascorbic acid) used as an ancillary treatment, and why?

A

Ancillary treatment for methemoglobinemia by reducing Fe3+ to Fe2+

28
Q

What is the name of a Vitamin C (ascorbic acid) deficiency? What are 7 signs/symptoms of this? What systemic effect does Vitamin C deficiency (scurvy) have?

A

Scurvy - (1) swollen gums (2) bruising (3) hemarthrosis (4) anemia (5) poor wound healing (6) perifollicular and subperiosteal hemorrhages (7) “corkscrew” hair; Weakened immune response; Think: “vitamin C deficiency causes sCurvy due to a Collagen synthesis defect.”

29
Q

What are 5 symptoms associated with excess Vitamin C (ascorbic acid)?

A

(1) Nausea (2) Vomiting (3) Diarrhea (4) Fatigue (5) Calcium oxalate nephrolithiasis

30
Q

What risk can Vitamin C (ascorbic acid) excess increase, and in what patient population?

A

Can increase risk of iron toxicity in predisposed individuals (e.g., those with transfusions, hereditary hemochromatosis).

31
Q

What is another name for Vitamin D2? What is its source?

A

D2 = ergocalciferol - ingested from plants.

32
Q

What is another name for Vitamin D3? What are its sources?

A

D3 = cholecalciferol - consumed in milk, formed in sun-exposed skin (stratum basale).

33
Q

What is the active versus storage form of Vitamin D3?

A

25-OH D3 = storage form; 1,25-(OH)2D3 (calcitriol) = active form

34
Q

For what part of the body is drinking milk good, and why?

A

Drinking milk (fortified with vitamin D) is good for bones

35
Q

What are 2 functions of Vitamin D?

A

(1) Increase intestinal absorption of calcium and phosphate (2) Increase bone mineralization

36
Q

What are 3 conditions associated with Vitamin D deficiency?

A

(1) Rickets in children (bone pain and deformity) (2) Osteomalacia in adults (bone pain and muscle weakness) (3) Hypocalcemic tetany

37
Q

What special patient population should receive oral vitamin D?

A

Breastfed infants should receive oral vitamin D.

38
Q

What are 3 factors that exacerbate Vitamin D deficiency?

A

Deficiency is exacerbated by (1) low sun exposure (2) pigmented skin (3) prematurity.

39
Q

What are 4 symptoms associated with excess Vitamin D?

A

(1) Hypercalcemia (2) Hypercalciuria (3) Loss of appetite (4) Stupor

40
Q

In what condition is Vitamin D excess seen, and why?

A

Seen in sarcoidosis (increased activation of vitamin D by epithelioid macrophages)

41
Q

What deficiency causes Rickets? How may Rickets appear on x-ray?

A

Vitamin D deficiency; Bowing of femurs