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USMLE Step 1 > Vitamins > Flashcards

Flashcards in Vitamins Deck (14):
1

B1

Thiamine, TPP
- PD, alpha-KGD, Transketolase (RBC test), branched-chain ketoacid dehydrogenase
Def: Wernicke-Korsakoff, Dry beriberi (polyneuritis, symmetric muscle wasting), Wet beriberi (dilated cardiomyopathy HF, edema)

Dx by increased RBC transketolase activity w/ B1

2

B2

Riboflavin (component of FAD, FMN [=2ATP])
- Succinate dehydrogenase

Def:Cheilosis (inflamed lips, scaling and fissures), Corneal vascularization

3

B3

Niacin (NAD+ [3ATP], NADP+)
- derived from tryptophan, synthesis requires B2 and B6 or diet
- lowers VLDL and raises HDL

Def: glossitis,
Hartnup, malignant carcinoid, isoniazid ---- severe def. ----pellagra (Diarrhea, Dementia/hallucinations, Dermatitis (C3/4 broad collar rash= 'Casal necklace', hyper pigmentation of sun exposed limbs))

Excess: facial flushing (PG's NOT histamine - take aspirin w/ niacin), hyperglycemia, hyperuricemia

4

B5

Pantothenic acid (CoA)
- component of CoA and fatty acid synthase
Def: dermatitis, enteritis, alopecia, adrenal insufficiency

5

B6

Pyridoxine (PLP)
- converted to pyridoxal phosphate (PLP) - cofactor in transamination (ALT and AST), decarboxylation, glycogen phosphorylase, synthesis of cystathionine/heme/niacin/histamine/serotonin/Epi/NE/dopamine/GABA

def (caused by isoniazid and OCP): convulsions, hyperirritable, peripheral neuropathy, sideroblastic anemia

6

B7

Biotin
- Pyruvate carboxylase, Acetyl-CoA carboxylase, Propionyl-CoA carboxylase

Def- rare (AB's or raw eggs whites): dermatitis, alopecia, enteritis, lactic acidosis, surplus of odd chain f.a.'s

7

B9

Folate
- converted to THF
- leafy green vegetables, absorbed in jejunum

Def: increased homocysteine, normal methylmalonic acid
- caused by phenytoin, sulphonamides, methotrexate
- most common def in USA

8

B12

Cobalamin
- cofactor for: homocysteine methyltransferase and methylmalonyl -CoA mutase

9

C

ascorbic acid
- antioxidant, reduces iron to Fe2+ (increases absorption)
- needed for dopamine beta-hydroxylase (dopamine---NE)
- corkscrew hair with scurvy

Excess: calcium oxalate nephrolithiasis, increased risk of Fe toxicity (on top of transfusions, hemochromatosis)

10

A

- Antioxidant
- Treats measles, AML-M3 and acne
- Liver and leafy vegetables
Def: nyctalopia (night blindness), xerosis cutis (dry scaly skin), keratomalacia (corneal degen.), Bitot spots (conjunctival keratin buildup), immunosuppression

Excess: Acute toxicity, Chronic tox. (alopecia, dry skin, hepatic, pseudotumor cerebri), Teratogenic (cleft palate, cardiac, microcephaly, fetal death)

11

D

D2=ergocalciferol (veg)
D3=cholecalciferol (milk, stratum basale)
25-OH D3=storage form
1,25-(OH)2 D3=calcitrol=active form

Deficiency: exacerbated by pigmented skin, premature
Excess: granulomatous disease (sarcoidosis, TB, Hodgkins and non-Hodgkins lymphoma)

12

E

Tocopherol/tocotrienol
- Antioxidant (protect RBCs), enhances anti-coagulation of warfarin
Def: hemolytic anemia, acanthocytosis, B12 nerve issues

13

K

Phytomenadione, phylloquinone, phytonadione
- gamma carboxylation of glutamic acid residues on clotting factors (2, 7, 9, 10, C, S)
- made by intestinal flora
Def: Neonatal hemorrhage (not retinal) - normal bleeding time, increased PT and PTT

14

Zinc

- 100+ enzymes
- zinc finger (TF motifs)
Def: delayed wound healing, hypogonadism, decreased adult hair, dysgeusia, anosmia, acrodermatitis enteropathica
(may predispose to alcoholic cirrhosis)