USMLE Step 1 Prep: Vitamins
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15 terms
Terms | Definitions |
|---|---|
 Vitamin A | FXN: Retinol: Antioxident, used in visual pigments, essential for epithelial differentiation into special tissue (Pancrease, Muscus secreting), Tx Measels | Def: Night Blindness, Dry Skin | Excess: Arthralgias, fatigue, headache, skin changes, sore throught, alopecia, Teratogen (celft palate, cardiac defects) |
| vitamin B1 | FXN: Thiamine: in TPP, a cofactor for Pyruvate dehydrogenase (glycolysis), a-ketoglutarate dehydrogenase (Crebs), Transketolase (HMP shunt), branched chain AA dehydrogenase | Def: Impaired glucose breakdown -> ATP depletion (high aerobic tissues hurt first like heart and brain), BeriBeri / wernicke-Korsakoff = confusion, opthalmoplegia, ataxia, confabulation, memory loss (permenant). Dmg to medial dorsal nucleus of thalamus and mamillary bodies. Dry = Neurological, Wet = Dry + high output heart failure (dialated cardiomyopathy) | Excess: N/A |
| Vitamin B2 | FXN: Riboflavin: Cofactor for Red Ox rxns. (FADH2/ FMN). | Def: Cheilosis (inflammation of libs, scaling of fissures of the mouth, corneal vascularization | Excess: N/A |
| Vitamin B3 | FXN: niacin: Constitutie NAD/NADP for Redox rxns. Derived from TRYPTOPHAN, Synthesis req B6. | Def: Glossitis, Pellagra (Diarrhea, dermatitis, Dementia). Caused by Hartnup (dec tryptophan abs), maligant carcindoid (inc tryp met), or INH (dec b6) | Excess: Facial Flushing (most often seen with pharm use for hyperlipidemia) |
| Vitamin B5 | FXN: Pantothenate: Component of CoA, and cofactor for Acyl transferers, also used in FA synthase | Def: Dermatitis, enteritis, alopecia, adrenal insuffiency | Excess: N/A |
| Vitamin B6 | FXN: Pyridoxine: converted to pyridoxal phosphate (cofactor for transaminations), used in decarboxylations, glycogen phosphoryase, heme synthesis, Niacin (B3) from tryptophan) | Def: Convulsions, hyperirritable, peripheral neuropathy, sideroblastic anemia. (caused by INH) | Excess: N/A |
| Vitamin B12 | FXN: Cobalamin: Cofactor of homocystien methyltransferase (CH3) and methylmalonyl CoA mutase. Large reserve pool (years) in liver. Absorption req intrinsic factor | Def: Macrocytic megaloblastic anemia, hypersegment PMN, neurolgical symptoms (abnormal myelin fxn) | Excess: N/A |
| Vitamin C | FXN: Ascorbic Acid: Antioxidant, Facilitates iron absorption (keeps it in reduced state), needed for hydroxylation of proline / lysine in collagen synthesis, for Dopamine b-hydroxylase (DA-> NE) | Def: Scurvy: swollen gums, bruising, hemarthrosis, anemia, poor wound healing. Dec immune response | Excess: N/A |
| Vitamin D | FXN: D2 = ergocalciferol (ingest from plants. D3 = cholecaciferol (ingest in milk, convert in skin from sun). 25-OHD3 = storage form (in adiopose), 1,25 OH D3 = calcitriol (active). FXN = inc absorption of Ca and phosphate, increaese Bone resorption. (build bones too). | Def: Rickets in children, Osteomalacia in adults. hypoCa tetany. Low amounts in Breast Milk | Excess: hyperCa, hyperCauria, loss of appetite and stupor (seen in sarcoidosis due to activation of D3 via macrophages) |
| Vitamin E | FXN: Antioxidant (protects erythrocytes and membranse from free radical dmg) | Def: Increase RBC fragility -> hemolytic anemia, muscle weakness, Posterior Column and Spinocerebellar tract demyelination | Excess: N/A |
| Vitamin K | FXN: Catalizes the gamma-carboxylation of glutamic acid for clotting factors. Synthesize by intestinal flora. (Factors 2,7,9,10) | Def: Neonatal hemorrhage (inc PT and PTT but normal BT) due to sterile intestines in neonates, also after long broad spectrum antibiotics | Excess: N/A |
| Folic Acid | FXN: Converted to tetrahydrofolate (THF) used as coenzyme for 1 carbon transfers. Important in DNA/RNA base synthesis. Found in green leaves) | Def: Macrocytic megaloblastic anemia, no neurolgical symptoms, MC defiency in US, seen in alcholics and pregnancy (neural tube defects) | Excess: N/A |
| S-adenosyl-methionine | FXN: ATP + methioine -> SAM. It is used to transfer methyl units. (Most notably the creation of homocystein from methionine) Regeneratio is dependent on B12+folate. Used for Conversion of NE to Epi and Phosphocreatine productino | Def: N/A | Excess: N/A |
| Biotin | FXN: Cofactor for Carboxylations: Pyruvate Carboxylate, AcetylCoA Carboxylate, PriopioylCoA Carboxylase | Def: Rare -> dermatitis, alopecia, enteritis (MC due raw eggs (bound by Avidin in egg whites) or antibiotics) | Excess: N/A |
| Zinc | FXN: Essential for enzyme activity (zinc fingers) | Def: Delayed wound healing, hypogonadism, dec hair in adults, dysgeusia anosmia | Excess: N/A |
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