Anti-Metabolites and Anti-Vitamins Overview
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Questions and Answers

What effect does galactoflavine have on growth when riboflavin intake is low?

  • Promotes rapid growth
  • Has no effect on growth
  • Inhibits growth (correct)
  • Enhances metabolic processes
  • Which anti-folate substance is commonly used as an anti-cancer agent?

  • Sulfanilamide
  • Methotrexate (correct)
  • Pyrimethamine
  • 4-aminopterin
  • Which structure is formed by replacing glutamic acid with aspartic acid in the folate structure?

  • Methotrexate
  • 4-aminopterin
  • Methyl folic acid
  • Pteroyl aspartic acid (correct)
  • Which of the following compounds is a naturally occurring biotin antagonist found in raw egg albumin?

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

    What structural change occurs in des-oxypyridoxine?

    <p>Replacement of –CH2OH group at position 4 with a methyl group</p> Signup and view all the answers

    Which anti-nicotinic substance is known for having activity in both bacteria and animals?

    <p>3-Acetyl pyridine</p> Signup and view all the answers

    Which vitamin does anti-vitamin K substances reduce the action of, leading to decreased blood clotting?

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

    How does heating affect the harmful effects of agaritine, a vitamin B6 antagonist?

    <p>Greatly reduces harmful effects</p> Signup and view all the answers

    What is a common feature of anti-metabolites?

    <p>They inhibit specific metabolic processes by mimicking metabolites.</p> Signup and view all the answers

    Which method describes how anti-vitamins typically act?

    <p>Competitive inhibition of vitamins in metabolic processes.</p> Signup and view all the answers

    What effect do anti-vitamins have on human nutrition according to the information provided?

    <p>They can result in vitamin deficiencies by blocking vitamin actions.</p> Signup and view all the answers

    What distinguishes pyrithiamin as an anti-thiamin?

    <p>It closely resembles thiamin due to a specific structural modification.</p> Signup and view all the answers

    What characteristic of oxythiamin makes it an active thiamin antagonist?

    <p>Presence of an OH group replacing the NH2 group.</p> Signup and view all the answers

    Which of the following statements about anti-riboflavin substances is accurate?

    <p>Synthetic versions have shown potency in both bacteria and animals.</p> Signup and view all the answers

    Which synthetic anti-riboflavin compound replaces the methyl groups with Cl-?

    <p>Dichlororiboflavine.</p> Signup and view all the answers

    What is a known limitation of thiaminase as an anti-thiamin?

    <p>It is heat-sensitive and can be destroyed by cooking.</p> Signup and view all the answers

    Study Notes

    Anti-Metabolites

    • Anti-metabolites are chemicals that inhibit specific metabolic processes. They act by inhibiting the action of a metabolite involved in the normal process.
    • Anti-metabolites typically have similar structures to the chemicals they inhibit, but they do not react in the same way.

    Anti-Vitamins

    • Some anti-vitamins are structural analogues of vitamins, blocking their actions.
    • Their action is a form of competitive inhibition and is reversible.
    • Some compete with vitamins in specific metabolic processes.
    • Others react with vitamins, making them unavailable.
    • Anti-vitamins can affect nutrition by replacing and destroying vitamin availability, resulting in vitamin deficiency.
    • Anti-vitamins are used in disease control by denying vitamins to disease-causing agents, such as bacteria, while ensuring human processes are not affected.

    Examples of Anti-vitamins

    Anti-Thiamin

    • Pyrithiamin: Replaces the sulfur in thiamin with a vinylene group. Competes with thiamin due to similar structure; strongly antagonistic in humans and animals.
    • Oxythiamin: Replaces the amino group with a hydroxyl group, creating an active thiamin antagonist, causing thiamin deficiency in mice.
    • Thiaminase: An enzyme that hydrolyzes thiamin. Found in some fresh fish (e.g., carp) and plants (e.g., ferns); mostly heat-sensitive.

    Anti-Riboflavin

    • No naturally occurring anti-riboflavin substances are currently known.
    • Synthetic anti-riboflavin substances have been discovered and show potency in both bacteria and animals.
      • D-araboflavine: Formed by inverting the hydroxyl group on the ribose at position 3. An antagonist in rats.
      • Iso-riboflavine: Formed by shifting a methyl group from position 6 to 8. Antagonist in animals.
      • Dichlororiboflavine: Formed by replacing methyl groups at positions 6 and 7 with chlorine. A bacteriostatic agent.
      • Galactoflavine: An antagonist of riboflavin in rats, especially when riboflavin intake is low; inhibits growth, reversible by increased riboflavin.

    Anti-Folates

    • Anti-folate substances antagonize the action of folic acid, directly inhibiting cell division.
    • This principle is used to treat cancers.
      • Example: Methotrexate is an anti-cancer agent and an immune suppressant.
      • Pteroyl aspartic acid: Formed by replacing glutamic acid with aspartic acid in the folate structure. Antagonistic in bacteria and chicken, but not in rats.
      • Other examples: Sulfanilamide (anti-bacterial agent), Pyrimethamine (anti-malarial drug), methyl folic acid, 4-aminopterin.

    Anti-Niacin

    • 3-Acetyl pyridine: Formed by replacing the CONH2 group with an acetyl group. Anti-niacin activity in both bacteria and animals.
    • Pyridine-3-sulfonic acid: Formed by replacing the CONH2 group with a sulfonic group, with similar anti-niacin activity to 3-acetyl pyridine.

    Anti-Biotin

    • Avidin: A naturally occurring biotin antagonist found in raw egg albumin of birds, reptiles, and amphibians. Binds to biotin, making it unavailable for cell metabolism.
    • Other antagonists include desthiobiotin and biotin sulphonic acid

    Anti-Pyridoxine

    • Agaritine: A vitamin B6 antagonist naturally found in some plants and mushrooms. Harmful effects are reduced by heating.
    • Des-oxypyridoxine: Formed by replacing -CH2OH at position 4 with a methyl group. Antagonistic in mice, chicken, and monkeys.
    • Methoxypyridoxine: Formed by replacing the OH group at position 4 with a –OCH3 group. Found in seeds of Ginkgo biloba; a neurotoxin.

    Anti-Vitamin K

    • Reduces vitamin K action, decreasing blood clotting.
    • Used as a poison for small animals (e.g., rats) and as an anticoagulant (blood thinner), such as coumadins (e.g. Warfarin), which is used in the treatment of thrombosis.

    Reading Assignment

    • Explain why sulfanilamides act as folic acid antagonists in bacteria but not in humans.

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    Anti-Metabolites PDF

    Description

    This quiz explores the concepts of anti-metabolites and anti-vitamins, including their chemical structures and mechanisms of action. You'll learn how these compounds affect metabolic processes and nutrition, as well as their role in disease control through competitive inhibition. Test your understanding of the examples and implications of these substances.

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