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16 Cards in this Set
- Front
- Back
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Vitamin deficiencies occur in |
Alcohol abusers Elderly Patients w/ small bowel resections Food faddists Malnourished people in the developing world |
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Water-soluble Vitamins |
Precursors of coenzymes involved in metabolism All (-B12) are present in vegetables Deficiency of all (-B12) produces clinical symptoms w/in weeks [Vitamins - by definition cannot be synthesized ~ essential; -B3] |
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Vitamine B1 |
= Thiamin - Coenzyme (yellow) - carbohydrate metabolism (TCA): - pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, transketolase Deficiency: - mostly in heart & brain (nystagmus, ataxia) - Korsakoff's syndrome in alcohol abusers (should be always administered along w/ G to alcohol abusers) [G {malpractice} vs. G+B1] - irr., fatal - Beriberi - peripheral neuropathy & dilated cardiomyopathy [polished rice -> foot drop, moon heart] |
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Vitamine B2 |
= Riboflavin - Precursor of coenzymes FMN & FAD Deficiency: fissuring at the angles of the mouth, dermatitis, purple tongue [lo yield] |
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Vitamin B3 |
= Niacin ~ nicotinamide & nicotinic A - Precursors of NAD & NADP coenzymes - Can synthesize (!) niacin from Trp - Deficiency: pellagra ("sour skin") - dermatitis (photosensitive), diarrhea, dementia, death - Seen in patients w/ Hartnup disease (diminished Trp uptake) & carcinoid syndrome (altered Trp metabolism) - Used therapeutically to lower LDL & VLDL cholesterol in II-b hyperlipoproteinemia |
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Vitamin B5 |
= Panthothenic A - component of CoA - widely distributed in food (no known deficiency) [lo yield] |
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Vitamin B6 |
~ pyridoxine, pyridoxal, pyridoxamine - precursors of pyridoxal phosphate (-> AA rxns) - binds to anti-TB drug isoniazid (=> B6 routinely prescribed w/ isoniazid -| deficiency) - Deficiency: seizures |
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Vitamin B7 |
= Biotin - coenzyme in carboxylation rxns - Covalently bound to Lys residues of biotin-containing enzymes - Eating >20 raw eggs (~biotin-binding P avidin = highest possible affinity) per day => deficiency - Deficiency: dermatitis, glossitis, and nausea |
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Vitamin B9 |
= Folate ->DHFR -> THF - necessary for 1-C metabolism (including purine & T = DNA synthesis) - Deficiency: megaloblastic anemia (fetuses: neural tube defects: spina bifida, anencephaly) - Supplemented in "enriched" foods since 1998 (- Methotrexate --| DHFR ~ cancer therapy) |
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Vitamin B12 |
= Cobalamin - (porphyrin-like + Co) precursor of coenzymes: - methylcobalamin - THF metabolism (Homoc. -> Met) in blood - deoxyadenosylcobalamin - FA oxidation in neurons - Not produced in plants; significant body stores (although H2O-soluble) - Absorption requires intrinsic factor (IF - parietal cells |-- autoimmunity) - Deficiency (vegans, pt's w/ pernicious anemia ~ no IF): -- Pernicious (megaloblastic) anemia, dementia -- Subacute combined degeneration of spinal cord (despite enough B9) - Deficiency treatment - IM B12 injections (circumventing IF) |
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Vitamin C |
= Ascorbic A - necessary for post-translational hydroxylation of Lys & Pro in collagen - Deficiency: scurvy (bleeding gums), corkscrew hair follicle hemorrhages, bleeding underneath periosteum -> bone pain, poor wound healing - Overdose: oxalic A kidney stones |
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Fat-soluble vitamins |
Often present in pt's w/ fat malabsorption - pancreatic insufficiency, intestine dissection (sprue) Stored in the body & metabolized slowly -> deficiency develops only after months Not just coenzymes - more diverse fxns [Vitamins - by definition cannot be synthesized ~ essential; -D] |
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Vitamin A |
= retinol, retinal (rhodopsin), RA (-> differentiation in epithelial cells) - animal sources or β-carotene in plants - fat-soluble & heat-resistant (cooking carrots in oil) - Deficiency: night/permanent blindness, xeropthalmia, Bitot's spots - Used in treatment of acne & psoriasis - Hypervitaminosis A -> skin rash, liver dmg, ↑ intracranial pressure; teratogenic |
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Vitamin D |
- Can be produced: UV radiation / obtained from animal/plant tissues - hydroxylation (liver -> kidney/bone/placenta) ->> calcitriol (active form) = steroid hormone -> Ca absorption in intestine - US milk fortified w/ vit D - Deficiency: demineralization of bones -> osteomalacia (bone pain, microfractures); failure to mineralize developing bones (-> rickets) - Risk factors: lack of milk consumption, dark skin, low sun exposure - Overdose -> hypercalcanaemia ("bones, stones & abdominal moans") |
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Vitamin E |
- antioxidant protecting lipid membranes - Deficiency: RBC fragility [lo yield] |
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Vitamin K |
- Needed for post-translational carboxylation of Glu -> Ca binding by clotting factors (prothrombin) - Produced in intestinal bacteria - Deficiency: hemorrhage w/ long PT (prothrombin time) - Clinically administered to: -- premature infants (lack intestinal bacteria) -- adults on long-term antibiotic therapy - Can be blocked by coumadin -| clotting (pt's w/ prosthetic heart valves) |
