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

Question 1

What is another name for Vitamin B9?

Answer 1

Vitamin B9 (folic acid)

Question 2

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

Answer 2

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

Question 3

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

Answer 3

Important for the synthesis of nitrogenous bases in DNA and RNA

Question 4

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

Answer 4

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

Question 5

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

Answer 5

Small reserve pool stored primarily in the liver

Question 6

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?

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Vitamin B9 (folic acid)

Question 9

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

Answer 9

Seen in alcoholism and pregnancy

Question 10

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

Answer 10

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

Question 11

Why is supplemental maternal folic acid given early in pregnancy?

Answer 11

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

Question 12

What is the function of Vitamin B12 (cobalamin)?

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

Associated within increased serum homocysteine and methylmalonic acid levels.

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Prolonged deficiency => irreversible nerve damage

Question 17

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

Answer 17

Found in animal products; Synthesized only by microorganisms

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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).

Question 20

What is diagnostic for pernicious anemia?

Answer 20

Anti-intrinsic factor antibodies diagnostic for pernicious anemia

Question 21

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.

Answer 21

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

Question 22

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.

Answer 22

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

Question 23

What is another name for Vitamin B12?

Answer 23

Vitamin B12 (cobalamin)

Question 24

What is another name for Vitamin C?

Answer 24

Vitamin C (ascorbic acid)

Question 25

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

Answer 25

(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.

Question 26

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

Answer 26

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

Question 27

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

Answer 27

Ancillary treatment for methemoglobinemia by reducing Fe3+ to Fe2+

Question 28

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?

Answer 28

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."

Question 29

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

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

D2 = ergocalciferol - ingested from plants.

Question 32

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

Answer 32

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

Question 33

What is the active versus storage form of Vitamin D3?

Answer 33

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

Question 34

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

Answer 34

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

Question 35

What are 2 functions of Vitamin D?

Answer 35

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

Question 36

What are 3 conditions associated with Vitamin D deficiency?

Answer 36

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

Question 37

What special patient population should receive oral vitamin D?

Answer 37

Breastfed infants should receive oral vitamin D.

Question 38

What are 3 factors that exacerbate Vitamin D deficiency?

Answer 38

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

Question 39

What are 4 symptoms associated with excess Vitamin D?

Answer 39

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

Question 40

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

Answer 40

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

Question 41

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

Answer 41

Vitamin D deficiency; Bowing of femurs