31: Vitamins - Perry

Question 1

define vitamins

Answer 1

Heterogeneous group of organic compounds required in small amounts for cellular functions; cannot be synthesized in adequate amounts

Question 2

biological roles of vitamins

Answer 2

Essential cofactors in enzymatic reactions
Biological regulatory molecules
Antioxidants

Question 3

water soluble vitamins

Answer 3

Water soluble (B vitamins, vitamin C) – absorbed in portal blood, circulate in free form, not stored

can have tolerable upper limits (adverse effects at high levels) but not toxic

Question 4

fat soluble vitamins

Answer 4

Fat soluble – (A, D, E, K) absorption is 40-90% via bile salts; require carrier protein for circulation, stored to some extent by body fat

can become toxic in lg. doses (have tolerable upper limits)

Question 5

describe how folate and cobalamin work together

Answer 5

Joint role in one-carbon transfer pathway

Necessary for production and maintenance of new cells, DNA/RNA synthesis

Folate works as a substrate for cobalamin

Deficiency of cobalamin can lead to a “methyl trap” in methylation pathway

Question 6

cobalmin deficiency –>

folate deficiency –>

Answer 6

pernicious anemia

Megaloblastic anemia, neural tube defects

Question 7

describe cobalamin structurally

Answer 7

Cobalamin contains a cobalt ion complexed in a ring structure (corrin ring)

R group can attach to various groups including methyl group to yield methylcobalamin

Animal sources only

Question 8

most common B12 deficiency

Answer 8

Pernicious anemia

Parietal cells fail to secrete intrinsic factor.
Risk increases with age (occurring in up to 15% of elderly), gastrointestinal conditions/surgeries (Crohn’s, atrophic gastritis, autoimmune destruction of gastric mucosa, gastric bypass)

Question 9

measures B12 and IF deficiency

Answer 9

schilling test

Question 10

describe megaloblastic anemia

Answer 10

maturation of hematopoietic precursor cells is disrupted due to defect in DNA synthesis; white and red blood cells are enlarged; many cells die in bone marrow which leads to anemia

Question 11

B12 low and folate normal =

normal B12 and high folate =

b12 low and folate high =

Answer 11

Macrocytosis, anemia,
cognitive impairment

No cognitive impairment

Odds ratio = 5 for cognitive impairment and anemia (*masks the B12 deficiency and shows up worse)

Question 12

Antioxidant

Answer 12

refers to any molecule capable of stabilizing or deactivating free radicals before they attack cells - act as electron donors to stabilize the reactive species – different types based on solubility

Question 13

describe vit D

Answer 13

Able to synthesize if adequate UV light

Little from diet

Can be considered a hormone – synthesized at 1 site, converted into active hormone at another site, exerts action at target tissues

Question 14

functions of vit D

Answer 14

Kidney, bone, intestine –> maintain blood calcium
May be involved in cell differentiation
Immunity

Question 15

role of B1 Thiamin

Answer 15

Oxidative decarboxylation of α-keto acids and 2-keto sugars

deficiency: Beriberi, muscle weakness, anorexia, tachycardia, edema
sources: east, pork, legumes

Question 16

role of B2

Riboflavin

Answer 16

Electron (hydrogen) transfer reactions

deficiency: Cheilosis, glossitis, hyperemia and edema of pharyngeal and oral mucous membranes
sources: Liver, beef, dairy

Question 17

role of B3 niacin

Answer 17

Electron (hydrogen) transfer reactions

deficiency: Pellagra, diarrhea, dermatitis, confusion, dementia
sources: Tuna, liver, poultry, beef, mushrooms

Question 18

role of pantothenic acid

Answer 18

Acyl transfer reactions

deficiency: Very rare, numbness, tingling of extremities, fatigue
sources: Widespread, highest in egg yolk, liver, kidney

Question 19

role of B6

Pyridoxine

Answer 19

Coenzyme in many transamination and decarbxylation reactions

deficiency: Dermatitis, glossitis, convulsions
sources: Liver, fish, meat

Question 20

role of biotin

Answer 20

CO2 transfer reactions, carboxylation reactions

deficiency: Very rare, anorexia, nausea, glossitis, dermatitis
sources: Yeast, liver, kidney; synthesized by microflora

Question 21

role of folic acid

Answer 21

One carbon methyl transfers, amino acid metabolism

deficiency: Megaloblastic anemia, fatigue, depression, confusion
sources: Brewer’s yeast, liver, green leafy vegetables, lima beans

Question 22

role of B12 cobalamin

Answer 22

Methylation of homocysteine to methionine, conversion of methylmalonyl CoA to succinyl CoA

deficiency: Megaloblastic anemia, degeneration of peripheral nerves, glossitis
sources: Meat, fish, shellfish, poultry, milk

Question 23

fole of vit C or ascorbic acid

Answer 23

Antioxidant, role in collagen synthesis, immune function, absorption of non-heme iron

deficiency: Scurvy, fatigue, slow wound healing, bleeding gums, rupture of capillaries
sources: Fruits and vegetables

Question 24

role of beta-carotene and its derivative retinol

Answer 24

Vision, metabolites involved in growth failure, growth and differentiation of epithelial, nervous, and bone tissue, immune function

deficiency:Children: poor dark adaptation, xerosis, keratomalacia
Adults: night blindness, xeroderma

sources:Liver, dark green leafy vegetables, orange fruits and vegetables

Question 25

role of vit D cholecalciferol

Answer 25

Regulator of bone metabolism, primarily calcium, other roles emerging

deficiency:Children: rickets
Adults: osteomalacia

sources:Skin synthesis, liver, fish, fortified dairy, eggs

Question 26

role of vit D alpha-tocopherol

Answer 26

Antioxidant,
Enzymatic activities
Gene expression
Cell signaling

deficiency:Infants: anemia
Children & adults: neuropathy, myopathy

sources:Vegetable oil, nuts, green vegetables

Question 27

role of vit K

Answer 27

Blood coagulation
Bone growth

deficiency:Children: hemorrhagic disease of newborns
Adults: defective blood clotting

sources: Gut flora, dark green leafy vegetables