Vitamins and Their Functions
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Questions and Answers

What is a primary characteristic of vitamins?

  • Vitamins can be synthesized in sufficient quantities by the organism.
  • Vitamins are essential micronutrients required in small quantities. (correct)
  • Vitamins are inorganic molecules.
  • Vitamins provide all necessary calories for energy.

    • Which of the following statements about vitamin deficiencies is true?

  • Micronutrient synthesis in the body can eliminate vitamin deficiencies.
  • Vitamin deficiencies are only caused by dietary shortages.
  • Vitamin deficiencies do not occur in older people.
  • Medical treatments such as antibiotics can lead to vitamin deficiencies. (correct)

    • How are vitamins classified?

  • According to their mechanical properties.
  • Based on their caloric content.
  • By their solubility and biological function. (correct)
  • Into primary and secondary categories.

    • Which of the following vitamins is NOT fat-soluble?

    <p>Vitamin B12</p> Signup and view all the answers

    What can result from malnutrition or certain medical conditions?

    <p>Hypovitaminosis or avitaminosis.</p> Signup and view all the answers

    Which vitamins can typically be stored in the body?

    <p>Vitamin A, Vitamin D, Vitamin E, and Vitamin K</p> Signup and view all the answers

    What happens when there is an overdose of certain vitamins?

    <p>Fat-soluble vitamins A and D can lead to hypervitaminosis.</p> Signup and view all the answers

    How are the daily vitamin requirements of an individual influenced?

    <p>By variables like age, sex, and physiological conditions.</p> Signup and view all the answers

    What role does the enzyme activated by the G protein transducin play in the visual process?

    <p>It breaks down the second messenger cGMP.</p> Signup and view all the answers

    Which vitamin is a precursor of the hormone retinoic acid?

    <p>Vitamin A</p> Signup and view all the answers

    Which type of photoreceptor cell is responsible for vision in low light conditions?

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

    What is the primary function of retinal in the human body?

    <p>Functions in visual processes</p> Signup and view all the answers

    What effect does Vitamin A deficiency have on vision?

    <p>Causes night blindness and visual impairment</p> Signup and view all the answers

    What is the maximum wavelength of light absorption for rhodopsin?

    <p>500 nm</p> Signup and view all the answers

    Which vitamin is known to vary in requirement due to physiological conditions such as pregnancy?

    <p>Vitamin B-9</p> Signup and view all the answers

    Which statement about the allosteric conformational change in rhodopsin after photon absorption is true?

    <p>It allows rhodopsin to bind and activate transducin.</p> Signup and view all the answers

    Which vitamin is a fat-soluble vitamin found in meat-containing diets?

    <p>Vitamin A</p> Signup and view all the answers

    What role does retinal play in the structure of rhodopsin?

    <p>It is bound as an aldimine to the ε-amino group of a lysine residue.</p> Signup and view all the answers

    Which of the following vitamins is exclusively classified as a water-soluble vitamin?

    <p>Vitamin B-7</p> Signup and view all the answers

    Which vitamin can be synthesized from β-carotene?

    <p>Vitamin A</p> Signup and view all the answers

    What initiates the signal cascade in rod cells when light is detected?

    <p>Activation of rhodopsin by light</p> Signup and view all the answers

    What is a potential consequence of hyperpolarization of light-sensitive cells in the retina?

    <p>Inhibition of visual signaling</p> Signup and view all the answers

    What role does retinoic acid play in cellular processes?

    <p>Influences transcription of genes</p> Signup and view all the answers

    Which vitamin is associated with the coenzymes involved in metabolic processes?

    <p>Vitamin B-3</p> Signup and view all the answers

    What are some consequences of vitamin A toxicity?

    <p>Cessation of menstruation and headaches</p> Signup and view all the answers

    Which hormone is a precursor to the active form of vitamin D?

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

    Which hormone primarily acts to decrease blood calcium levels?

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

    What is the primary role of parathyroid hormone (PTH)?

    <p>To stimulate calcitriol production and increase blood calcium levels</p> Signup and view all the answers

    What deficiency can lead to osteomalacia in adults?

    <p>Vitamin D deficiency</p> Signup and view all the answers

    What is the role of cGMP in rod cells during dark conditions?

    <p>It maintains the ion channels in an open state.</p> Signup and view all the answers

    Which event occurs first when light activates rod cells?

    <p>Activation of cGMP phosphodiesterase by the GTP-bound α_subunit.</p> Signup and view all the answers

    Which substance regulates calcium metabolism in healthy adults?

    <p>Calcitriol and parathyroid hormone together with calcitonin</p> Signup and view all the answers

    How much calcium is typically absorbed daily in healthy adults?

    <p>Around 1g</p> Signup and view all the answers

    What occurs after the hydrolysis of cGMP in rod cells?

    <p>Closure of ion channels due to cGMP dissociation.</p> Signup and view all the answers

    What happens during the recovery phase of rod cells after exposure to light?

    <p>cGMP levels are restored, reopening cation channels.</p> Signup and view all the answers

    What is a primary food source high in calcium?

    <p>Cheese and milk products</p> Signup and view all the answers

    What is one consequence of vitamin A deficiency?

    <p>Development of night blindness.</p> Signup and view all the answers

    Which of the following mechanisms restores cGMP levels in rod cells after light exposure?

    <p>Activation of guanylate cyclase by increased Ca2+.</p> Signup and view all the answers

    What is the function of the isomerase in the visual signal cascade?

    <p>It converts all-trans-retinal back to 11-cis-retinal.</p> Signup and view all the answers

    What triggers the hyperpolarization of rod cells in response to light?

    <p>Closure of sodium and calcium ion channels.</p> Signup and view all the answers

    What is the primary function of vitamin E in biological membranes?

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

    Which of the following is a consequence of vitamin E deficiency?

    <p>Axonal degeneration</p> Signup and view all the answers

    How does vitamin E prevent lipid peroxidation?

    <p>By donating an H atom to free radicals</p> Signup and view all the answers

    Which types of foods are good sources of vitamin E?

    <p>Vegetable oils and nuts</p> Signup and view all the answers

    What type of chemical structure is characteristic of vitamin E?

    <p>A chromane ring</p> Signup and view all the answers

    What is a common feature of reactive oxygen species (ROS)?

    <p>They contain unpaired electrons.</p> Signup and view all the answers

    Which radical is produced when dioxygen gains an extra electron?

    <p>Superoxide radical</p> Signup and view all the answers

    What impact do oxidized LDL particles have on health?

    <p>They are linked to atherogenesis and coronary artery disease.</p> Signup and view all the answers

    Study Notes

    Human Metabolism - Biochemistry

    • ATP (Adenosine Triphosphate): A crucial energy molecule in the human body. It carries energy in its phosphate bonds.

    • Mitochondria: Cellular structures responsible for ATP production. They have inner and outer membranes. The inner membrane is critical for oxidative phosphorylation, a process that generates ATP.

    Vitamins

    • Vitamins are organic micronutrients, essential for proper metabolic function. Unlike other nutrients, the body cannot synthesize them in sufficient quantities. They must be obtained through the diet.

    • Types of Vitamins: Vitamins are categorized as either water-soluble or fat-soluble. Water-soluble vitamins, like vitamin C and B vitamins, are generally not stored in the body and need to be consumed regularly. Fat-soluble vitamins (vitamins A, D, E, and K) are stored in the body's fat.

    • Vitamin Function: Vitamins act as coenzymes or precursors to coenzymes.

    Vitamin A

    • Function: Retinal is involved in visual processes as the pigment in rhodopsin and also works as a hormone.

    • Source: Retinoids (like retinol) are present in meat. B-carotene, a precursor to vitamin A, is found in fruits and vegetables (especially carrots).

    • Deficiencies: Can result in night blindness, visual impairment, and growth disorders.

    Vitamin D (calciol, cholecalciferol)

    • Function: A precursor, calcitriol (1,25-dihydroxycholecalciferol), regulates calcium metabolism.

    • Source: Synthesized in the skin upon exposure to UV light. Also found in some foods.

    • Deficiencies: Results in rickets in children and osteomalacia in adults, impacting bone mineralization. Key role in balancing calcium levels.

    Vitamin E (Tocopherol)

    • Function: Antioxidant, protecting unsaturated lipids in cell membranes from oxidative damage by reactive oxygen species (ROS).

    • Source: Found in plant-based foods.

    Vitamin K

    • Function: Essential for the carboxylation of glutamate residues resulting in Ca2+ binding sites in several calcium-dependent proteins (essential for blood clotting). Vitamin K is produced by intestinal bacteria.
    • Source: Found in vegetables and made by bacteria in the gut

    Reactive Oxygen Species (ROS)

    • Formation: ROS are generated during cellular processes.

    • Role: Both necessary and dangerous. Production is a part of normal cellular function, while excessive ROS is dangerous to the cell. Necessary for various functions but excessive ROS is harmful.

    Visual Processes

    • Rhodopsin: A light-sensitive pigment in rod cells of the retina that undergoes a conformational change when exposed to light leading to a signal cascade where ultimately light is detected.
    • Photoreceptor Cells: Rods and cones, that transmit light info to the brain.
    • Signal Cascade: A series of biochemical events that transmit light signals from the photoreceptors to the brain.

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