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USMLE > Nutrition > Flashcards

Nutrition Flashcards

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USMLE® Step 1 flashcards
1
Q

Name vitamin B1

A

Thiamine: TPP (precursor organic cofactor)

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2
Q

Name vitamin B2

A

Riboflavin: FAD, FMN (precursor organic cofactor)

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3
Q

Name vitamin B3

A

Niacin: NAD+ (precursor organic cofactor)

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4
Q

Name vitamin B5

A

Pantothenic acid : CoA (precursor organic cofactor)

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5
Q

Name vitamin B6

A

Pyridoxine: PLP (precursor organic cofactor)

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6
Q

Name vitamin B7

A

Biotin

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7
Q

Name vitamin B9

A

Folic acid

Storage 3-4 months (liver)

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8
Q

Name vitamin B12

A

Cobalamin

Storage 3-4 years (liver)

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9
Q

Name vitamine C

A

Ascorbic acid (coenzyme)

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10
Q

Fat soluble vitamins

A

ADEK

Deficit in malabsorption diseases : cystic fibrosis, celiac disease; mineral oil intake

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11
Q

Vitamin A function

A

Antioxydant
Constituent of visual pigments
Essential normal differenciation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells)
Prevents squamous metaplasia
Treat measles (rougeole)
Treat acute promyelocytic leukemia (trans-retinoic acid)
Treat acne (isotretinoin)

Found in liver, leafy vegetables

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12
Q

Vitamin A deficiency

A

Night blindness (nyctalopia)
Dry, scaly skin (xerosis cutis)
Corneal degeneration (keratomalacia) and dryness
Bitot spots (keratin -> white) on conjunctiva
Immunosuppression

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13
Q

Vitamin A excess

A

Acute toxicity : N, V, vertigo, blurred vision
Chronic toxicity : alopecia, dry skin, hepatic toxicity and enlargement, arthralgia, pseudotumor cerebri
Teratogenic : cleft palate, cardiac abnormalities (b-hCG negative + 2 forms of contraception if isotretinoin)

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14
Q

Vitamin B1 function

A

Thiamine pyrophosphate (TPP) = cofactor dehydrogenase enzyme reactions:

  • pyruvate dehydrogenase (links glycolysis to Krebs)
  • alpha-ketoglutarate dehydrogenase (Krebs)
  • transketolase (HMP shunt)
  • branched-chained ketoacid dehydrogenase
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15
Q

Vitamine B1 deficiency

A

Impaired glucose breakdown -> ATP depletion worsened by glucose infusion. High aerobic tissues (brain, heart) affected first

Dx: raised RBC transketolase after B1 given

In alcoholic or malnourished patients, give thiamine before dextrose to reduce risk of Wernicke-Korsakoff -> damage in medial dorsal nucleus of thalamus and mammillary bodies:

  • Confusion + Ophtalmoplegia + Ataxia )classic triad)
  • Confabulation
  • Personality change, permanent memory loss

Dry beriberi: polyneuritis, symmetrical muscle wasting

Wet beriberi: high-output cardiac failure (dilated cardiomyopathy), edema

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16
Q

Vitamin B2 function

A

Component of flavins FAD + FMN, cofactors in redox reactions (ex: succinate dehydrogenase in Krebs)

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17
Q

Vitamin B2 deficiency

A

Cheilosis (inflammation lips, scaling and fissures corners mouth)
Corneal vascularization

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18
Q

Vitamin B3 function

A

Constituent of NAD+, NADP+ used in redox reactions.
B3 synthesis using B2 and B6 derives from tryptophan (AA).
Treat DLPD : reduce VLDL, raises HDL

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19
Q

Vitamin B3 deficiency

A

Glossitis

Severe -> pellagra:
Diarrhea, Dementia (hallucination), Dermatitis, hyperpigmentation of sunexposed limbs, C3/C4 circumferential broad collar rash (casal necklace)

DDx pellagra:

  • B3 deficiency
  • Hartnup disease
  • Malignant carcinoid syndrome (raises tryptophan metabolism)
  • Isoniazid (reduces B6)
20
Q

Hartnup disease

A

Autosomal recessive

Deficiency in neutral AA (tryptophan) transporters in TCP and enterocytes -> neutral aminoaciduria and reduced absorption from gut -> reduced conversion of tryptophan to niacin -> pellagra-like symptoms

Tx: high-protein diet and nicotinic acid

21
Q

Vitamin B3 excess

A

Facial flushing (induced by Pg, not histamine; avoidable by taking ASA with niacin)
Hyperglycemia
Hyperuricemia

22
Q

Vitamin B5 function

A

Essential component of coenzyme A (CoA) and fatty acid synthase

23
Q

Vitamin B5 deficiency

A

Dermatitis, enteritis, alopecia, adrenal insufficiency

24
Q

Vitamin B6 function

A

Converted to pyridoxal phosphate (PLP) -> cofactor in transamination (ALT, AST), decarboxylation reactions, glycogen phosphorylase

Synthesis of cystathionine, heme, niacin, histamine, NT (5-HTP, epinephrine, NE, dopamine, GABA)

25
Q

Vitamin B6 deficiency

A

Convulsions, hyperirritability, peripheral neuropathy, sideroblastic anemias (impaired Hb synthesis) and iron excess)

Inducible by isoniazid and COC

26
Q

Vitamin B7 function

A

Cofactor for carboxylation enzymes (add 1 carbon group):

pyruvate carboxylase, acetyl-CoA carboxylase, propionyl-CoA carboxylase

27
Q

Vitamin B7 deficiency

A

Rare. Caused by ATB use or excessive ingestion of raw egg whites

Dermatitis, alopecia, enteritis.

28
Q

Vitamin B9 function

A

Converted to tetrahydrofolic acid (THF), coenzyme for 1-carbon transfer/methylation reactions
Important for synthesis of nitrogenous bases in DNA and RNA (nucleosides)

Found in leafy green vegetables. Absorption in jejunum.

29
Q

Vitamin B9 deficiency

A

Most common in USA. Seen in ROH, pregnancy, elderly

Macrocytic, megaloblastic anemia
Hypersegmented PMN
Glossitis
No neurologic symptoms

Dx : raised homocysteine, normal methylmalonic acid

30
Q

Vitamin B12 function

A

Cofactor for methionine synthase and methymalonyl-CoA -> important for DNA synthesis

Found in animal products. Synthesized by microorganisms.

31
Q

Vitamin B12 deficiency

A

Etiology: malabsorption (sprue, enteritis, dephyllobothium labum), lack of intrinsic factor (pernicious anemia, gastric bypass surgery), absence of terminal ileum (surgical resection), insufficient intake (vegan).

Sx: macrocytic, megaloblastic anemia
hypersegmented PMN
Paresthesia
Subacute combined degeneration due to abnormal myelin (dorsal columns, lateral corticospinal tracts and spinocerebellar tracts)
If prolonged -> irreversible nerve damage

Dx : anti-intrinsic factor Ac for pernicious anemia
Raisez homocysteine and methylmalonic acid levels

32
Q

Vitamin C function

A

Antioxydant
Facilitates iron absorption by reducing Fe2+ state
Necessary for hydroxylation of proline and lysine in collagen synthesis
Necessary for dopamine b-hydroxylase that converts dopamine to NE

Found in fruits and vegetables
Ancillary treatment for methemoglobinemia by reducing Fe3+ to Fe2+

33
Q

Vitamin C deficiency

A

Scurvy : swollen gums, bruising, petechiae, hemarthrosis, anemia, poor wound healing, perifollicular and subperiostal hemorrhages, corkscrew (tire bouchon) hair

34
Q

Vitamin C excess

A

N, V, D, fatigue, calcium oxalate nephrolithiasis

Raises risk of iron toxicity in predisposed individuals (hemochromatosis, transfusions)

35
Q

Vitamin D function

A

GI absorption of calcium and phosphate
Raises bone mineralization at low levels
Raises bone resorption at high levels

36
Q

Vitamin D deficiency

A

Ricketts in children : deformity genu varum
Osteomalacia in adults : bone pain and muscle weakness
Hypocalcemic tetany

FR: prematurity, pigmented skin, low sun exposure

37
Q

Vitamin D excess

A

Hypercalcemia, hypercalciuria, loss of appetite, stupor

38
Q

Vitamin E function

A

Antioxydant (protects RBC and membranes from free radical damade)
High dose might affect vit K metabolism (enhanced ACO effect of warfarin)

39
Q

Vitamin E deficiency

A

Hemolytic anemia, acanthocytosis, muscle waekness, posterior column and spinocerebellar tract demyelination

Similar to B12 but without megaloblastic anemia/hypersegmented PMN, and raised methylmalonic acid

40
Q

Vitamin K function

A

Cofactor on various proteins required for blood clothing (X, IX, VII, II, protein C and S)
Synthetized by intestinal flora
Inhibited by warfarin

41
Q

Vitamine K deficiency

A

Neonatal hemorrhage with raised PT, aPTT but normal bleeding time (sterile intestines)

Can also occur after prolonged broad spectrum ATB use

42
Q

Zinc function

A

Essential for activity of > 100 enzymes and formation of zinc fingers

43
Q

Zinc deficiency

A 
Delayed wound healing
Hypogonadism
Reduced adult hair (axillary, facial, pubic)
Dysgeusia
Anosmia
Acrodermatitis enteropathica
May predispose to alcoholic cirrhosis
44
Q

Kwashiorkor

A

Protein malnutrition:

  • skin lesions
  • edema (reduced oncotic pressure)
  • liver malfunction (fatty change because reduced apolipoprotein synthesis)
  • swollen abdomen
M alnutrition
E dema
A nemia
L iver (fatty)
S kin lesions (hyperkeratosis, hyperpigmentation)
45
Q

Marasmus

A

Malnutrition not causing edema. Diet deficient in calories but no nutrient is entirely missing

Muscle wasting (like dry beriberi)

USMLE (5 decks)

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