USMLE (Fach) / Biochemistry - Nutrition (Lektion)
In dieser Lektion befinden sich 18 Karteikarten
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- Vitamin A (retinol) - Antioxidant- Constituent of visual pigments (combines with opsin to produce rhodopsin)- Essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting ...
- Vitamin B1 (thiamine) In thiamine pyrophosphate (TPP), a cofactor for several dehydrogenase enzyme reactions:- Pyruvate dehydrogenase (links glycolysis to TCA cycle)- α-ketoglutarate dehydrogenase (TCA cycle)- Transketolase ...
- Vitamin B2 (riboflavin) Component of flavins FAD and FMN, used as cofactors in redox reactions eg, the succinate dehydrogenase reaction in the TCA cycle. Deficiency: - Individuals who do not consume dairy products (e.g., patients ...
- Vitamin B3 (niacin) - Constituent of NAD+/NADP+ - Derived from tryptophan; synthesis requires vitamins B2 and B6- Used to treat dyslipidemia; lowers VLDL and raises HDL Deficiency:- Glossitis- Pellagra: diarrhea, dementia (also ...
- Vitamin B6 (pyridoxine) - Converted to pyridoxal phosphate (PLP), a cofactor used in transamination (eg, ALT and AST), decarboxylation reactions, glycogen phosphorylase.- Synthesis of cystathionine, heme, niacin, histamine, ...
- Vitamin B7 (biotin) Cofactor for carboxylation enzymes (which add a 1-carbon group):- Pyruvate carboxylase: pyruvate (3C) → oxaloacetate (4C)- Acetyl-CoA carboxylase: acetyl CoA (2C) → malonyl-CoA (3C)- Propionyl-CoA ...
- Vitamin B9 (folate) Converted to tetrahydrofolic acid (THF), a coenzyme for 1-carbon transfer/methylation reactions.- Important for the synthesis of nitrogenous bases in DNA and RNA. - Found in leafy green vegetables. - ...
- Vitamin B12 (cobalamin) Cofactor for methionine synthase (transfers CH3 groups as methylcobalamine) and methylmalonyl-CoA mutase. Important for DNA synthesis. - Found in animal products. Synthesized only by microorganisms. - ...
- Vitamin C (ascorbic acid) - Antioxidant- Facilitates iron absorption by reducing it to Fe2+ state- Necessary for hydroxylation of proline and lysine in collagen synthesis- Necessary for dopamine β-hydroxylase (converts dopamine ...
- Vitamin D D3 (cholecalciferol) from exposure of skin (stratum basale) to sun, ingestion of fish, milk, plants.D2 (ergocalciferol) from ingestion of plants, fungi, yeasts.Both converted to 25-OH D3 (storage form) ...
- Vitamin E (tocopherol) Antioxidant (protects RBCs and membranes from free radical damage). Deficiency:- Hemolytic anaemia- Acanthocytosis- Muscle weakness- Posterior column and spinocerebellar tract demyelination→ Neurologic ...
- Vitamin K (phytomenadione) Includes phytomenadione, phylloquinone, phytonadione, menaquinone.Activated by epoxide reductase to the reduced form, which is a cofactor for the γ-carboxylation of glutamic acid residues on proteins ...
- Vitamin B5 (pantothenic acid) Essential component of coenzyme A (CoA, a cofactor for acyl transfers) and fatty acid synthase. Deficiency:- Dermatitis- Enteritis- Alopecia- Adrenal insufficiency
- Ethanol metabolism Ethanol → Acetaldehyd occurs in cytosol, microsomes (via CYP2E1 and NADPH), peroxisomes (via catalase and H2O2).Acetaldehyde → Acetate occurs in mitochondria. Fomepizole – inhibits alcohol dehydrogenase ...
- Zinc Mineral essential for the activity of 100+ enzymes. Important in the formation of zinc fingers (transcription factor motif). Cause: Long-term total parenteral nutrition, malabsorptive pathology Deficiency: ...
- Protein-energy malnutrition Kwashiorkor:- Protein malnutrition resulting in skin lesions, edema due to ↓ plasma oncotic pressure, liver malfunction (fatty change due to ↓ apolipoprotein synthesis).- Clinical picture is small ...
- Vitamins: water soluble B1 (thiamine: TPP)B2 (riboflavin: FAD, FMN)B3 (niacin: NAD+)B5 (pantothenic acid: CoA)B6 (pyridoxine: PLP)B7 (biotin)B9 (folate)B12 (cobalamin)C (ascorbic acid) - All wash out easily from body except ...
- Vitamins: fat soluble A, D, E, K. Absorption dependent on gut and pancreas. Toxicity more common than for water-soluble vitamins because fat-soluble vitamins accumulate in fat. Malabsorption syndromes with steatorrhea (eg, ...