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USMLE Step 1 Random Facts > Vitamins > Flashcards

Flashcards in Vitamins Deck (43):
1

B1

thiamine: TPP

2

B2

riboflavin: FAD, FMN

3

B3

niacin: NAD+

4

B5

pantothenic acid: CoA

5

B6

pyridoxine: PLP

6

B7

biotin

7

B9

folate

8

B12

cobalamin

9

C

ascorbic acid

10

fat soluble vitamins

A,D,E,K

11

vit A (retinol)

-antioxidant
-visual pigments (retinal)
-normal diff of epith cells into specialized tissues
-prevents squamous metaplasia
-tx of measles, AML M3
-in liver (esp polar bears), leafy vegetables, beta-carotene (carrots)

12

vit A (retinol) deficiency

-night blindness
-dry skin
-bitot spots (dry spots on conjunctiva)
-keratomalacia (wrinkling/clouding of cornea)
-xerophthalmia
-corneal ulcerations

13

vit A (retinol) excess

-arthralgias, fatigue, HA, sore throat
-alopecia
-skin changes (oranging of skin, dry/pruritic skin)
-teratogenic (cleft palate, cardiac abnorm)
-increased ICP (pseudotumor cerebri)

14

vit B1

-TPP = active form
-cofactor for enzymes in decarboxylation rxns (pyruvate DH, alpha-ketoglutarate DH, transketolase, branched-chain AA DH)

15

vit B1 deficiency

-ATP depletion (from impaired glucose breakdown) --> WORSENED w/ glucose infusion
-brain/heart affected first (highly aerobic)
-Wernicke-Korsakoff synd
-Dry beriberi (neuritis, symm muscle wasting)
-Wet beriberi (high-output cardiac failure, dilated cardiomyopathy, edema)
-seen in alcoholics, in malnutrition, and in pts on dialysis

16

vit B2

-cofactor in oxidation/reduction
-FAD (cofactor for succinate DH + component of ETC complex II)
-FMN (component of ETC complex I)

17

vit B2 deficiency

-"mouth and eyes"
-cheilosis (inflamm of lips, scaling/fissures @ corners of mouth)
-corneal vascularization
-dermatitis
-stomatitis
-glossitis

18

vit B3

-NAD+/NADP - used in redox rxns
-derived from tryptophan
-synth req B6 + B2

19

vit B3 deficiency

-glossitis
-**pellagra: (if severe); aka caused by:
-Hartnup dz - decreased tryptophan absorp
-malig carcinoid synd (increased tryptophan metab)
-INH (decreases B6)

20

vit B3 excess

facial flushing

21

vit B5

-component of CoA + fatty acid synthase

22

vit B5 deficiency

-dermatitis
-enteritis
-alopecia
-adrenal insuff

23

vit B6

-pyridoxal phosphate = active form
-used in transamination (ALT, AST) and decarboxylation rxns
-cofactor for glycogen phosphorylase
-synth of cystathionine, heme, niacin, histamine, NT (serotonin, epinephrine, NE, GABA)

24

vit B6 deficiency

-convulsions (bc decreased GABA)
-hyperirritability
-periph neuropathy (deficiency inducible by INH + oral contraceptives)
-sideroblastic anemias (due to impaired Hb synth and Fe excess) - bc lack of ALA-S enzyme

25

best enzyme to test B1 deficiency?

transketolase

26

"tea and toast" diet deficiency?

B3 (niacin)

27

vit B2 impt for what enzymes?

-succinate DH (TCA)
-fatty-acyl CoA DH (beta-oxidation)
-glycerol phosphate shuttle

28

B7 cofactor for?

carboxylation rxns:

-pyruvate carboxylase (pyruvate (3C) --> OA (4C)) - used in gluconeogenesis

-acetyl-CoA carboxylase (acetyl-CoA (2C) --> malonyl-CoA (3C)) - used in FA synthesis

-propionyl-CoA carboxylase (propionyl-CoA (3C) --> methylmalonyl-CoA (4C)) - used to metabolize odd-chain FA, Val, Met, Ile, Thr ("VOMIT" pathway)

29

B7 deficiency caused by? causes?

by avidin in egg whites or AB use
causes dermatitis, alopecia, enteritis; also fasting hypoglycemia (loss of pyruvate carboxylase)

30

deficiency of B9 seen in?

alcoholics and pregnant pts
also w/ several drugs (phenytoin, sulfonamides, MTX, TMP)

31

B9 function =?

converted to THF = coenzyme for 1C transfer/methylation rxns
impt for synth/repair of DNA and synth of nitrogenous bases in DNA + RNA

32

B12 function?

cofactor for:
-homocysteine methyltransferase (untraps inactive folate from storage [N5-methyl-THF])
-methylmalonyl-CoA mutase (part of "VOMIT" pathway)

33

deficiency of vit B12 seen w/?

-malabsorption (enteritis, sprue, Diphyllobothrium latum)
-lack of intrinsic factor
-absence of terminal ileum (Crohn's disese)

34

labs show what in B12 def?

increased methylmalonic acid and homocysteine levels

35

SAM and methionine regen depend on?

vit B12 and folate

36

4 functions of vit C?

-antioxidant
-facilitate iron absorption by keeping in in reduced (Fe2+) state
-nec for hydroxylation of proline and lysine in collagen synth
-nec for dopamine-beta-hydroxylase (converts dopamine --> NE)

37

vit D deficiency seen in patients that:

-breast feed
-have dark skin

38

vit E function?

protect RBCs and membrane lipids from ROS

39

vit E deficiency?

-hemolytic anemia (bc increased fragility of RBCs)

-(proximal) muscle weakness

-***posterior column and spinocerebellar tract demyelination (mimics Friedrich's ataxia; ataxia, dysarthria, loss of proprioception/vibratory sense)

-decrease serum phospholipids and cause infertility

40

vit E tx for?

abetalipoproteinemia

41

vit E excess?

hemorrhagic stroke (in adults)
necrotizing enterocolitis (in infants)

42

vit K function

gamma-carboxylation of glutamic acid residues (put another COO- group)

43

vit K deficiency seen in pts that?

-breast feed
-after prolonged use of broad spectrum AB or phenytoin (wipe out intestinal gut flora)