Biochemistry-Nutrition Flashcards Preview

USMLE Step 1 > Biochemistry-Nutrition > Flashcards

Flashcards in Biochemistry-Nutrition Deck (31):
1

thiamine

B1, TPP

2

riboflavin

B2, FAD, FMN

3

niacin

B3, NAD+

4

pantothenic acid

B5, CoA

5

pyridoxine

B6, PLP

6

biotin

B7

7

folate

B9

8

cobalamin

B12

9

ascorbic acid

VitC

10

Vitamin A

differentiation of epithelial cells; prevents squamous metaplasia; used to treat measles, AML (M3)

11

Vitamin A deficiency

night blindness, dry/scaly skin, alopecia, corneal degeneration, immune supression

12

Vit A toxicity

arthralgias, scaly skin, cerebral edema, osteoporosis; teratogenic so need pregnancy test before starting isotretinoin for severe acne

13

TPP is a cofactor for which reactions?

ATP: alpha-ketoglutarate dehydrogenase (TCA cycle); transketolase (HPM shunt in RBCs); pyruvate dehydrogenase (links glycolysis to TCA cycle; pyruvate to acetyl CoA); branched chain ketoacid dehydrogenase

14

confusion, opthalmoplegia, ataxia + confabulation, etc

Wernicke Korsakoff syndrome--damage to medial dorsal nucleus of thalamus, mamillary bodies; make diagnosis by increased RBC transketolase activity after thiamine

15

poylneuritis, synmmetrical muscle wasting

dry beriberi (thiamine deficiency)

16

high output cardiac failure (dilated cardiomypathy); edema

wet beriberi (thiamine deficiency)

17

B1 deficiency

impaired glucose breakdown, ATP depletion worsened by glucose infusion, if suspect, always give B1 first!

18

What reaction in citric acid cycle uses vitamin B2?

B2-->riboflavin-->FAD/FMN-->succinate dehydrogenase (makes 2 ATP)

19

B2 deficiency:

cheilosis, corneal vascularization

20

What vitamins are needed to make B3?

B3 is niacin. tryptophan is precursor. Niacin synthesis requires B2 and B6.

21

What causes B3 deficiency? Symptoms

Hartnup disease (decreased tryptophan absorption); malignant carcinoid (increased tryptophan use); isoniazid (decreased B6); Diarrhea, dementia, dermatitis

22

Niacin overdose?

facial flushing (prostaglandin mediated) hyperglycemia, hyperuricemia

23

Vitamin B5 deficiency

dermatitis, enteritis, alopecia, adrenal insufficiency

24

What is B6 used for

converted to pyridoxal phosphate, cofactor used in transamination, decarboxylation reactions, glycogen phosphorylase, synthesis of cystathione, heme, niacin, histamine, and neurotransmitters (serotonin, epinephrine, norepinephrine, dopamine, GABA)

25

B6 deficiency?

convulsions, hyperirratibility, peripheral neuropathy, sideroblastic anemias (impared hemeoglobin synthesis and iron excess)

26

B7 is used for:

composes biotin, cofactor for carboxylation enzymes

27

eating too many egg whites

B7 deficiency (avidin binds biotin)

28

Use of B9?

converted to tetrahydrofolate (THF); 1-carbon transfer/methylation rxns; synthesis of nitrogenous bases

29

What distinguishes B9 from B12 deficiency?

B12 has neurological symptoms, increased methymalonic acid levels

30

Vitamin C

facilitates iron absorption by reducing it to Fe2+ states; necessary for hydroxylation of proline/lysine in collagen snthesis; necessary for dopamine B-hydroxylase to convert dopamine to NE

31

hemolytic anemia, acanthocytosis, muscle weakness, posterior column and spinocerebellar tract demyelination

Vit E deficiency--can appear similar to B12, but does not have megaloblastic anemia, hypersegmented neutrophils, or increased serum MMA levels