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Questions and Answers
Histamine is a vasoconstrictor.
Histamine is a vasoconstrictor.
False
Dopamine is an intermediate in the formation of adrenaline.
Dopamine is an intermediate in the formation of adrenaline.
True
GABA is a vasoconstrictor and a neurohumoral agent in the venoms of wasps.
GABA is a vasoconstrictor and a neurohumoral agent in the venoms of wasps.
False
Transamination involves the transfer of a keto group from a keto-acid to an amino acid.
Transamination involves the transfer of a keto group from a keto-acid to an amino acid.
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Glutamate dehydrogenase is a simple enzyme that catalyzes the oxidative deamination of L-glutamate.
Glutamate dehydrogenase is a simple enzyme that catalyzes the oxidative deamination of L-glutamate.
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D-Amino acid oxidase is present in the liver, kidney, and brain.
D-Amino acid oxidase is present in the liver, kidney, and brain.
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Serine and Threonine are deaminated by specific deaminases in a reaction preceded by hydration.
Serine and Threonine are deaminated by specific deaminases in a reaction preceded by hydration.
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The liver is not a major site of nitrogen metabolism in the body.
The liver is not a major site of nitrogen metabolism in the body.
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The carbon skeletons produced from amino acids are degraded to form 5 metabolic products.
The carbon skeletons produced from amino acids are degraded to form 5 metabolic products.
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Amino acid catabolism begins by adding the amino group.
Amino acid catabolism begins by adding the amino group.
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Lysine is a guianidinium ion that is always protonated.
Lysine is a guianidinium ion that is always protonated.
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Threonine has one chiral carbon.
Threonine has one chiral carbon.
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Asparagine is an amide of glutamic acid.
Asparagine is an amide of glutamic acid.
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Leucine is a glycogenic amino acid.
Leucine is a glycogenic amino acid.
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Isoleucine is only a ketogenic amino acid.
Isoleucine is only a ketogenic amino acid.
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Amino acid molecules in the amino acid pool come only from dietary proteins.
Amino acid molecules in the amino acid pool come only from dietary proteins.
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Porphyrin is synthesized from fatty acids.
Porphyrin is synthesized from fatty acids.
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A positive nitrogen balance occurs when nitrogen intake equals nitrogen loss.
A positive nitrogen balance occurs when nitrogen intake equals nitrogen loss.
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The reaction of deamination involves the removal of the β-amino group from amino acids.
The reaction of deamination involves the removal of the β-amino group from amino acids.
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Oxidative deamination is a reversible biochemical reaction.
Oxidative deamination is a reversible biochemical reaction.
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Transamination reactions are catalyzed by Oxidase enzymes.
Transamination reactions are catalyzed by Oxidase enzymes.
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Lysine is an amino acid that participates in transamination reactions.
Lysine is an amino acid that participates in transamination reactions.
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Pyridoxal phosphate (PLP) serves as the cofactor for oxidative deamination reactions.
Pyridoxal phosphate (PLP) serves as the cofactor for oxidative deamination reactions.
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Vitamin B6 is derived from pyridoxal phosphate (PLP).
Vitamin B6 is derived from pyridoxal phosphate (PLP).
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Ornithine transcarbamoylase is the enzyme responsible for the conversion of citrulline to arginosuccinate.
Ornithine transcarbamoylase is the enzyme responsible for the conversion of citrulline to arginosuccinate.
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The urea cycle occurs exclusively in the cytoplasm.
The urea cycle occurs exclusively in the cytoplasm.
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Argininosuccinate synthetase is the enzyme responsible for the conversion of citrulline to arginine.
Argininosuccinate synthetase is the enzyme responsible for the conversion of citrulline to arginine.
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The urea cycle is activated by N-acetylglutamate.
The urea cycle is activated by N-acetylglutamate.
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Pyrophosphatase is involved in the reaction catalyzed by argininosuccinate synthetase.
Pyrophosphatase is involved in the reaction catalyzed by argininosuccinate synthetase.
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The enzyme arginase is responsible for the conversion of arginine to ornithine and urea.
The enzyme arginase is responsible for the conversion of arginine to ornithine and urea.
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The urea cycle requires four ATP molecules.
The urea cycle requires four ATP molecules.
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Ornithine is regenerated at the end of the urea cycle.
Ornithine is regenerated at the end of the urea cycle.
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Urea is produced in the kidneys of ureotelic animals.
Urea is produced in the kidneys of ureotelic animals.
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Arginase is found in significant amounts in the kidney.
Arginase is found in significant amounts in the kidney.
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The net reaction for the urea cycle involves the production of urea and fumarate.
The net reaction for the urea cycle involves the production of urea and fumarate.
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Fumarate is a component of the urea cycle.
Fumarate is a component of the urea cycle.
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Oxaloacetate can be used in energy generation or converted to glucose or aspartate.
Oxaloacetate can be used in energy generation or converted to glucose or aspartate.
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Urea is eliminated in the urine by the liver.
Urea is eliminated in the urine by the liver.
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Study Notes
Amino Acid Classification
- Lysine is a diamino acid, protonated at pH 7.0
- Arginine is a guianidinium ion, always protonated, and the most basic amino acid
Polar Uncharged Amino Acids
- Have polar side groups, are hydrophilic, and can form hydrogen bonds
- Examples: Serine (Ser, S), Threonine (Thr, T), Asparagine (Asn, N), Glutamine (Gln, Q)
Classification of Amino Acids Based on Metabolic Intermediates
- Glycogenic amino acids are catabolized to pyruvate, α-ketoglutarate, succinyl CoA, fumarate, or oxaloacetate
- Examples: Alanine, Asparagine, Aspartate, Arginine, Cysteine, Glutamate, Glutamine, Histidine, Methionine, Proline, Serine, Threonine, and Valine
- Ketogenic amino acids are catabolized to acetyl CoA or acetoacetyl CoA
- Examples: Leucine and Lysine
- Some amino acids are both glycogenic and ketogenic
- Examples: Isoleucine, Phenylalanine, Tryptophan, and Tyrosine
Catabolism of Carbon Chains from Amino Acids
- Complex series of reactions involved in the breakdown of amino acids
- Amino acid molecules are continuously synthesized and degraded
- Amino acid pool is a source of amino acids for various metabolic processes
Nitrogen Balance
- Nitrogen intake (primarily amino acids) equals nitrogen loss in healthy adults
- Positive nitrogen balance occurs in growing children, pregnant women, and recuperating patients
General Reactions of Amino Acids
- Amino acids can be decarboxylated to amines, which have important physiological roles
- Examples: Histidine → Histamine, Dopa → Dopamine, and 5-hydroxy tryptophan → Serotonin
Transamination
- Involves the transfer of an amino group from an amino acid to a keto-acid to form the corresponding amino acid
- Catalyzed by aminotransferases, which require pyridoxal phosphate as a prosthetic group
- Examples: AST and ALT
Oxidative Deamination
- Glutamate dehydrogenase catalyzes the oxidative deamination of L-glutamate to α-ketoglutarate and ammonium
- Occurs in the mitochondria of hepatocytes
- ATP is an allosteric inhibitor, while GDP and ADP are allosteric activators
Non-Oxidative Deamination
- Serine and Threonine can be deaminated directly by specific deaminases
- Examples: Serine → Pyruvate + NH4+, Threonine → α-ketobutyrate + NH4+
Hydrolytic Deamination
- Hydrolysis of the amide groups of glutamine and asparagine
- Examples: Glutamine → Glutamate + NH4+, Asparagine → Aspartate + NH4+
Direct Deamination
- Histidine → Urocanate + NH3
Urea Synthesis
- The liver is the major site of nitrogen metabolism in the body
- Urea synthesis involves the removal of the amino group from amino acids
- The carbon skeletons produced from amino acids are degraded to form various metabolic products
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Description
This quiz covers the properties and classification of amino acids, including lysine, arginine, serine, threonine, and asparagine, including their protonation states and hydrogen bonding capabilities.
