Nutrition II

Question 1

What are the symptoms of vitamin B6 deficiency?

Answer 1

Convulsions, hyperirritability, peripheral neuropathy, sieroblastic anemias due to impaired hemoglobin synthesis and iron excess (p.91)

Question 2

What can cause a B6 deficiency?

Answer 2

Izoniazid; oral contraceptives (p.91)

Question 3

What is the function of Vitamin B7 (biotin)?

Answer 3

Serves as a cofactor for carboxylation enxymes which add 1 carbon group: pyruvate carboxylase (pyruvate –> oxaloacetate); Acetyl-Co-A Carboxylase (acetyl-CoA –> malonyl-CoA); Propionyl-CoA carboxylase (propionyl CoA –> methylmalonyl-CoA) (p.92)

Question 4

What are the causes of vitamin B7 deficiency?

Answer 4

Quite rare; caused by antibiotic use or excessive ingestion of raw eggs (avidin) (p.92)

Question 5

What are the symptoms of vitamin B7 deficiency?

Answer 5

Dermatitis, alopecia, enteritis (p.92)

Question 6

What is the function of Vitamin B9 (folic acid)?

Answer 6

Converts to tetrahydrofolate (THF), a coenzyme for 1-carbon transfer/methylation reactions and is important for the synthesis of nitrogenous bases in DNA and RNA (p.92)

Question 7

What foods are rich in Vitamin B9?

Answer 7

Leafy green vegetables (p.92)

Question 8

Is Vitamin B9 stored?

Answer 8

Small reserve pool primarily in the liver (p.92)

Question 9

What are the symptoms of Vitamin B9 deficiency?

Answer 9

Macrocytic, megaloblastic anemia; no neurologic symptoms (as opposed to vitamin B12 deficiency) (p.92)

Question 10

What can cause a Vitamin B9 deficiency?

Answer 10

Alcoholism, pregnancy, drugs (phenytoin, sulfonamides, MTX) (p.92)

Question 11

What is the function of Vitamin B12 (cobalamin)?

Answer 11

Cofactor for homocysteine methyltransferase (transfers CH3 groups as methylcobalamin) and methylmalonyl-CoA mutase (p.93)

Question 12

Where is cobalmin synthesized?

Answer 12

Only by microorganisms (p.93)

Question 13

What are the three most common causes of Vitamin B12 deficiency?

Answer 13

Malabsorption (sprue, enteritis, Diphyllobothrium lactum), lack of intrinsic factor (pernicious anemia, gastric bypass), or absence of terminal ileum (Crohn’s disease) (p.93)

Question 14

What test is used to detect the etiology of a B12 deficiency?

Answer 14

Schilling test (p.93)

Question 15

What is the clinical presentation of B12 deficiency?

Answer 15

Macrocytic, megaloblastic anemia, hypersegmented PMNs, neurologic symptoms (paresthesias, subacute combined degeneration) due to abnormal myelin. Prolonged deficiency leads to irreversible damage (p.93)

Question 16

What is the composition of S-adenosyl-methionine?

Answer 16

ATP + methionine –> SAM (p.93)

Question 17

What is the function of SAM?

Answer 17

SAM transfers methyl units and is required for the conversion of NE to epinephrine

Question 18

What cofactors are necessary for the regeneration of methionine and SAM?

Answer 18

Vitamin B12 and Folate (p.93)

Question 19

What is the function of Vitamin C?

Answer 19

An antioxidant that also facilitates iron absorption by keeping iron in its Fe2+ reduced state. Necessary for the hydroxylation of proline and lysine in collagen synthesis (scurvy –> collagen synthesis defect) and necessary for dopamine B hydroxylase which converts dopamine to NE (p.94)

Question 20

What are the symptoms of Vitamin C overdose?

Answer 20

Nausea, vomiting, diarrhea, fatigue, sleep problems, increased risk of iron toxicity (for pts with transfusions or hereditary hemochromatosis) (p.94)

Question 21

What are the four forms of Vitamin D?

Answer 21

D2= ergocalciferol; D3= cholecalciferol; 25-OH D3, 1,25- (OH)2D3= calcitrol (p.94)

Question 22

How are adequate sources of Vitamins D2 and D3 attained?

Answer 22

D2- ingested from plants; D3- consumed in milk and formed in sun exposed skin (p.94)

Question 23

What is the difference between 25-OH D3 and 1,25-(OH)2D3?

Answer 23

25-OH D3 is the storage form; 1,25- (OH)2D3 is the active form (p.94)

Question 24

What is the function of Vitamin D?

Answer 24

Increases intestinal absorption of calcium and phosphate, increases bone mineralization (p.94)

Question 25

What are four consequences of Vitamin D deficiency?

Answer 25

Rickets in children; osteomalacia in adults; hypocalcemic tetany; decreased Vitamin D in breast milk (p.94)