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Questions and Answers
What is the primary difference between deamination and transamination reactions?
What is the primary difference between deamination and transamination reactions?
Ammonia in the body is typically converted to the ammonium ion at physiological pH.
Ammonia in the body is typically converted to the ammonium ion at physiological pH.
True
Name two enzymes that are involved in the removal of ammonia/ammonium ions from body cells.
Name two enzymes that are involved in the removal of ammonia/ammonium ions from body cells.
glutamate dehydrogenase and glutamine synthetase
The deamination of threonine forms ______ and ammonium ion.
The deamination of threonine forms ______ and ammonium ion.
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Which of the following is NOT a major source of ammonia/ammonium ions in the body?
Which of the following is NOT a major source of ammonia/ammonium ions in the body?
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Glutamate dehydrogenase uses an ammonia or ammonium ion and a-ketoglutarate to synthesize glutamine.
Glutamate dehydrogenase uses an ammonia or ammonium ion and a-ketoglutarate to synthesize glutamine.
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What type of enzymes generally carry out deamination reactions?
What type of enzymes generally carry out deamination reactions?
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The amide groups from glutamine and asparagine are removed in a process called ______.
The amide groups from glutamine and asparagine are removed in a process called ______.
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Match the following enzymes with their primary function related to ammonia/ammonium:
Match the following enzymes with their primary function related to ammonia/ammonium:
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Which of these amino acids is commonly deaminated?
Which of these amino acids is commonly deaminated?
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Which of the following best describes the primary product of a deamination reaction?
Which of the following best describes the primary product of a deamination reaction?
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Deamination reactions involve the transfer of an amino group to another molecule.
Deamination reactions involve the transfer of an amino group to another molecule.
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What is the name of the enzyme that deaminates threonine?
What is the name of the enzyme that deaminates threonine?
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The enzyme __________ uses an ammonia or ammonium ion and a-ketoglutarate to synthesize glutamate.
The enzyme __________ uses an ammonia or ammonium ion and a-ketoglutarate to synthesize glutamate.
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Match the following process with the type of organic compound it generates:
Match the following process with the type of organic compound it generates:
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What role does carbamoyl phosphate synthetase I play in the removal of ammonia/ammonium ions?
What role does carbamoyl phosphate synthetase I play in the removal of ammonia/ammonium ions?
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Deamination reactions are irreversible.
Deamination reactions are irreversible.
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Where are the enzymes involved in ammonia removal primarily found?
Where are the enzymes involved in ammonia removal primarily found?
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Deamination reactions are generally carried out by lyases, dehydratases, or __________
Deamination reactions are generally carried out by lyases, dehydratases, or __________
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Besides deamination, what is another major source of ammonia in the body?
Besides deamination, what is another major source of ammonia in the body?
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What is released during a deamination reaction?
What is released during a deamination reaction?
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Deamination reactions include the transfer of an amino group to another compound.
Deamination reactions include the transfer of an amino group to another compound.
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What is the product of the deamination of threonine besides the ammonium ion?
What is the product of the deamination of threonine besides the ammonium ion?
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The deamidation of the amide groups from glutamine and asparagine results in the generation of ________.
The deamidation of the amide groups from glutamine and asparagine results in the generation of ________.
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Match the enzyme with the process:
Match the enzyme with the process:
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Which of these is a product of the deamination of an amino acid?
Which of these is a product of the deamination of an amino acid?
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The enzymes that assist in the removal of ammonia/ammonium ions are exclusively found in the liver.
The enzymes that assist in the removal of ammonia/ammonium ions are exclusively found in the liver.
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What is the name of the reversible reaction that converts ammonia to the ammonium ion?
What is the name of the reversible reaction that converts ammonia to the ammonium ion?
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Glutamate dehydrogenase uses an ammonium ion and a-ketoglutarate to synthesize ____.
Glutamate dehydrogenase uses an ammonium ion and a-ketoglutarate to synthesize ____.
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Which of the following groups of enzymes typically carry out deamination reactions?
Which of the following groups of enzymes typically carry out deamination reactions?
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What is the primary role of glutamate dehydrogenase in the context of ammonia/ammonium?
What is the primary role of glutamate dehydrogenase in the context of ammonia/ammonium?
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The deamination of amino acids always results in the formation of urea.
The deamination of amino acids always results in the formation of urea.
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What compound is formed when a-ketoglutarate reacts with an ammonia or ammonium ion?
What compound is formed when a-ketoglutarate reacts with an ammonia or ammonium ion?
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The enzyme threonine dehydratase catalyzes the deamination and dehydration of threonine to form _ and the ammonium ion.
The enzyme threonine dehydratase catalyzes the deamination and dehydration of threonine to form _ and the ammonium ion.
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Match the following enzymes with their respective role in the removal of ammonia/ammonium ions:
Match the following enzymes with their respective role in the removal of ammonia/ammonium ions:
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Which of the following processes directly generates ammonia/ammonium ions as part of amino acid metabolism?
Which of the following processes directly generates ammonia/ammonium ions as part of amino acid metabolism?
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The deamination of amino acids can only occur in the liver.
The deamination of amino acids can only occur in the liver.
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What two molecules are deaminated to produce ammonia?
What two molecules are deaminated to produce ammonia?
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Glutamine synthetase uses glutamate and ammonia to form ____
Glutamine synthetase uses glutamate and ammonia to form ____
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Match the deamination products with the corresponding amino acid that is deaminated:
Match the deamination products with the corresponding amino acid that is deaminated:
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Study Notes
Deamination of Amino Acids
- Deamination removes only the amino group from an amino acid, unlike transamination which transfers the amino group.
- The removed amino group becomes ammonia, which converts to the ammonium ion at physiological pH. This is a reversible reaction.
- Common deaminated amino acids include glutamate, histidine, serine, glycine, and threonine, though many can also be transaminated.
- Deamination is catalyzed by enzymes like lyases, dehydratases, or dehydrogenases, producing an α-keto acid and ammonia/ammonium ion.
- Threonine dehydratase deaminates and dehydrates threonine, forming α-ketobutyrate and an ammonium ion (illustrated in Figure 6.6).
Disposal of Ammonia
- Ammonia/ammonium ions come from deamination reactions, deamidation of glutamine/asparagine amide groups, ingested foods (e.g., cheeses, processed meats), and bacterial lysis of urea and amino acids in the GI tract.
- Removal is managed by glutamate dehydrogenase, glutamine synthetase, and carbamoyl phosphate synthetase I (part of the urea cycle).
- These enzymes are abundant in the liver and kidneys, as well as other organs.
Glutamate and Glutamine Synthesis
- Glutamate dehydrogenase synthesizes glutamate from ammonia/ammonium ion and α-ketoglutarate (reversible reaction).
- Glutamate releases ammonia/ammonium ion for urea synthesis or dispensable amino acid formation.
- Glutamine synthetase forms glutamine by attaching ammonia/ammonium ion to glutamate's γ-carboxyl group (ATP-dependent, requiring Mg²⁺ or Mn²⁺).
- Liver perivenous cells and other tissues synthesize glutamate and glutamine from ammonia/ammonium. Periportal hepatocytes are active in ureagenesis using ingested/intestinally-derived ammonia.
- Periportal hepatocytes handle most amino acid catabolism and use the resulting ammonia/ammonium for immediate urea synthesis.
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Description
Test your knowledge on the deamination process of amino acids and the disposal of ammonia. This quiz covers key concepts, enzymes involved, and specific amino acids affected by deamination. Challenge yourself with questions on how these biochemical processes work.
