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Questions and Answers
What effect does galactoflavine have on growth when riboflavin intake is low?
What effect does galactoflavine have on growth when riboflavin intake is low?
Which anti-folate substance is commonly used as an anti-cancer agent?
Which anti-folate substance is commonly used as an anti-cancer agent?
Which structure is formed by replacing glutamic acid with aspartic acid in the folate structure?
Which structure is formed by replacing glutamic acid with aspartic acid in the folate structure?
Which of the following compounds is a naturally occurring biotin antagonist found in raw egg albumin?
Which of the following compounds is a naturally occurring biotin antagonist found in raw egg albumin?
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What structural change occurs in des-oxypyridoxine?
What structural change occurs in des-oxypyridoxine?
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Which anti-nicotinic substance is known for having activity in both bacteria and animals?
Which anti-nicotinic substance is known for having activity in both bacteria and animals?
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Which vitamin does anti-vitamin K substances reduce the action of, leading to decreased blood clotting?
Which vitamin does anti-vitamin K substances reduce the action of, leading to decreased blood clotting?
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How does heating affect the harmful effects of agaritine, a vitamin B6 antagonist?
How does heating affect the harmful effects of agaritine, a vitamin B6 antagonist?
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What is a common feature of anti-metabolites?
What is a common feature of anti-metabolites?
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Which method describes how anti-vitamins typically act?
Which method describes how anti-vitamins typically act?
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What effect do anti-vitamins have on human nutrition according to the information provided?
What effect do anti-vitamins have on human nutrition according to the information provided?
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What distinguishes pyrithiamin as an anti-thiamin?
What distinguishes pyrithiamin as an anti-thiamin?
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What characteristic of oxythiamin makes it an active thiamin antagonist?
What characteristic of oxythiamin makes it an active thiamin antagonist?
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Which of the following statements about anti-riboflavin substances is accurate?
Which of the following statements about anti-riboflavin substances is accurate?
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Which synthetic anti-riboflavin compound replaces the methyl groups with Cl-?
Which synthetic anti-riboflavin compound replaces the methyl groups with Cl-?
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What is a known limitation of thiaminase as an anti-thiamin?
What is a known limitation of thiaminase as an anti-thiamin?
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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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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.