Tocopherols and Antioxidant Mechanism Quiz
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Questions and Answers

What is the main biochemical role of vitamin K?

  • Cofactor for carboxylation of glutamic acid residues in proteins involved in blood coagulation (correct)
  • Regulation of senescence and malignant transformations
  • Activation of tocopherols as antioxidants
  • Prevention of atherosclerosis

    • Which source is the most rich in tocopherols?

  • Liver
  • Seeds
  • Eggs
  • Vegetable oils (correct)

    • How do tocopheroxyl radicals get regenerated under antioxidant action?

  • They react with oxygen
  • Other molecules with antioxidant capacity can regenerate them (correct)
  • They combine with glutamic acid residues
  • They are eliminated from the body

    • What is the recommended daily allowance (RDA) for alpha-tocopherol in adults?

    <p>15 mg/day</p> Signup and view all the answers

    Which of the following is NOT a form of vitamin K?

    <p>Menadione (vitamin K3)</p> Signup and view all the answers

    What happens to the requirement for tocopherols as the intake of polyunsaturated fatty acids increases?

    <p>It increases</p> Signup and view all the answers

    What is the main biochemical role of vitamin E in the body?

    <p>Acts as an antioxidant in lipids</p> Signup and view all the answers

    Which of the following is a tocopherol compound of vitamin E?

    <p>α-tocopherol</p> Signup and view all the answers

    What can happen if there is a deficiency in vitamin E?

    <p>Oxidative damage to cell membranes</p> Signup and view all the answers

    How is vitamin D different from vitamin E in terms of storage and metabolism?

    <p>Vitamin E can be stored in the body, while vitamin D cannot be stored.</p> Signup and view all the answers

    Which type of compounds are tocotrienols in vitamin E?

    <p>Compounds with an isoprene chain attached</p> Signup and view all the answers

    What harmful effect can excess vitamin D intake have on the body?

    <p>Deposition of calcium salts in soft tissue</p> Signup and view all the answers

    What is the enzyme present in the human intestine that can cleave β-carotene into two molecules of retinal?

    <p>Carotenase</p> Signup and view all the answers

    What is the efficiency of the conversion of β-carotene into retinal compared to retinol?

    <p>1/12</p> Signup and view all the answers

    In which part of the molecule does the cleavage of β-carotene to retinal occur?

    <p>Middle</p> Signup and view all the answers

    What is the active form derived from the oxidation of retinol?

    <p>Retinal</p> Signup and view all the answers

    Which vitamin A form is essential in vision and exists as 11-cis retinal bound to protein opsin in rod cells of the retina?

    <p>Retinal</p> Signup and view all the answers

    In rod cell outer segments, what happens to 11-cis retinal upon illumination?

    <p>Isomerized into all-trans retinal</p> Signup and view all the answers

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