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Vitamins and Cofactors Flashcards

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  1. Pellagra, characterized by the 4 D's (Dermatitis, Diarrhea, Dementia, Death), is caused by deficiency of:

    Answer: Niacin (B3)

    Pellagra is caused by niacin (vitamin B3) deficiency, which impairs NAD⁺/NADP⁺-dependent redox reactions throughout the body, affecting skin, gut, and nervous system.

  2. Heme biosynthesis requires which vitamin as a cofactor for the enzyme delta-aminolevulinate synthase?

    Answer: Pyridoxal phosphate (B6)

    Delta-aminolevulinate synthase, which catalyzes the first committed step of heme synthesis, requires PLP (pyridoxal phosphate) as a cofactor for the condensation of glycine and succinyl-CoA.

  3. Scurvy results from Vitamin C deficiency primarily because without ascorbate:

    Answer: Prolyl and lysyl hydroxylases cannot function, impairing collagen synthesis

    Ascorbate is required to maintain the Fe²⁺ state of prolyl and lysyl hydroxylases; without it, hydroxylation of proline and lysine in collagen is deficient, preventing proper triple helix formation.

  4. Lipoic acid (lipoate) functions as a cofactor in alpha-keto acid dehydrogenase complexes by:

    Answer: Acting as a transient carrier of acyl groups and electrons via its dithiol/disulfide couple

    Lipoic acid is covalently bound to a lysine residue and cycles between its oxidized (disulfide) and reduced (dithiol) forms to transfer acyl groups and electrons during oxidative decarboxylation.

  5. Which vitamin deficiency is associated with Wernicke-Korsakoff syndrome, commonly seen in chronic alcoholics?

    Answer: Thiamine (B1)

    Thiamine deficiency due to poor diet and impaired absorption in alcoholics causes Wernicke-Korsakoff syndrome, characterized by ophthalmoplegia, ataxia, and confabulation from neuronal damage.

  6. Iron absorption from the diet is enhanced by Vitamin C because ascorbate:

    Answer: Reduces Fe³⁺ to Fe²⁺, which is better absorbed by DMT1

    Ascorbate reduces dietary non-heme iron from the insoluble Fe³⁺ (ferric) form to the soluble Fe²⁺ (ferrous) form, which is the substrate for the divalent metal transporter DMT1 in intestinal cells.

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