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Questions and Answers
What is the abbreviation used for the sum of glutamine and glutamate?
What is the abbreviation used for the sum of glutamine and glutamate?
What classification pertains to amino acids that the body cannot synthesize and must obtain from the diet?
What classification pertains to amino acids that the body cannot synthesize and must obtain from the diet?
Which amino acid has shown essentiality only for infants, with probable need in adults?
Which amino acid has shown essentiality only for infants, with probable need in adults?
What process involves the transcription of DNA into messenger RNA for protein synthesis?
What process involves the transcription of DNA into messenger RNA for protein synthesis?
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What does the term 'tRNA' refer to in the context of protein synthesis?
What does the term 'tRNA' refer to in the context of protein synthesis?
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When do dispensable amino acids become conditionally indispensable?
When do dispensable amino acids become conditionally indispensable?
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How many different amino acids are typically incorporated into mammalian proteins?
How many different amino acids are typically incorporated into mammalian proteins?
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Which of the following describes the functional groups attached to the central carbon of an amino acid?
Which of the following describes the functional groups attached to the central carbon of an amino acid?
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What is a precursor for the production of serine in humans?
What is a precursor for the production of serine in humans?
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Which amino acid is synthesized from serine by transferring a methylene group?
Which amino acid is synthesized from serine by transferring a methylene group?
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During amino acid metabolism, serine can be synthesized from which compound in humans?
During amino acid metabolism, serine can be synthesized from which compound in humans?
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Which of the following amino acids is known to contribute to the synthesis of glutathione?
Which of the following amino acids is known to contribute to the synthesis of glutathione?
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Which statement accurately describes the classification of proline?
Which statement accurately describes the classification of proline?
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What amino acid is required for the production of nitric oxide as indicated in the synthesis pathway?
What amino acid is required for the production of nitric oxide as indicated in the synthesis pathway?
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What is the primary purpose of gluconeogenesis?
What is the primary purpose of gluconeogenesis?
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In the context of dietary amino acids, which amino acid is mentioned as becoming indispensable if its precursor supply is low?
In the context of dietary amino acids, which amino acid is mentioned as becoming indispensable if its precursor supply is low?
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What type of pathways allow the reversible synthesis of serine from glycine?
What type of pathways allow the reversible synthesis of serine from glycine?
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Which amino acids are referred to as branched-chain amino acids (BCAAs)?
Which amino acids are referred to as branched-chain amino acids (BCAAs)?
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What is a significant consequence of losing more than 30% of body protein?
What is a significant consequence of losing more than 30% of body protein?
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Which of the following amino acids is NOT directly mentioned as a precursor to purines and pyrimidines?
Which of the following amino acids is NOT directly mentioned as a precursor to purines and pyrimidines?
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Which amino acid is produced from 3-phosphoglycerate and later aids in the formation of one-carbon units?
Which amino acid is produced from 3-phosphoglycerate and later aids in the formation of one-carbon units?
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Which amino acid forms a dimer called cystine?
Which amino acid forms a dimer called cystine?
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Which of the following pathways is NOT mentioned in relation to serine?
Which of the following pathways is NOT mentioned in relation to serine?
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Which amino acid has the highest molecular weight among the essential amino acids listed?
Which amino acid has the highest molecular weight among the essential amino acids listed?
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Which of the following amino acids is considered conditionally dispensable?
Which of the following amino acids is considered conditionally dispensable?
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What is the standard one-letter abbreviation for Threonine?
What is the standard one-letter abbreviation for Threonine?
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Which amino acid is vital for infants and is considered indispensable?
Which amino acid is vital for infants and is considered indispensable?
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What is the molecular weight of Serine?
What is the molecular weight of Serine?
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Which amino acid has the lowest molecular weight among the listed amino acids?
Which amino acid has the lowest molecular weight among the listed amino acids?
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Which of these amino acids is associated with protein quality assessment?
Which of these amino acids is associated with protein quality assessment?
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Tryptophan can be metabolized to produce which of the following?
Tryptophan can be metabolized to produce which of the following?
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Which amino acid is a precursor to catecholamines?
Which amino acid is a precursor to catecholamines?
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Which amino acid is considered nonessential?
Which amino acid is considered nonessential?
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Which amino acid is synthesized through the degradation of indispensable amino acids (IDAAs)?
Which amino acid is synthesized through the degradation of indispensable amino acids (IDAAs)?
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What role does methionine play in amino acid synthesis?
What role does methionine play in amino acid synthesis?
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Which amino acid contributes the amino group to cysteine synthesis?
Which amino acid contributes the amino group to cysteine synthesis?
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Which statement best differentiates between dispensable and indispensable amino acids?
Which statement best differentiates between dispensable and indispensable amino acids?
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What is the significance of 15N in the context of amino acids?
What is the significance of 15N in the context of amino acids?
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Which amino acid is NOT considered indispensable?
Which amino acid is NOT considered indispensable?
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What chemical process liberates TML from proteins?
What chemical process liberates TML from proteins?
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Which of the following amino acids contributes to the one-carbon methylation/transfer reactions?
Which of the following amino acids contributes to the one-carbon methylation/transfer reactions?
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What is the primary role of glutamate dehydrogenase in amino acid metabolism?
What is the primary role of glutamate dehydrogenase in amino acid metabolism?
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Why is histidine considered important in nutrition?
Why is histidine considered important in nutrition?
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Study Notes
Amino Acids
- When proteins are broken down, glutamine degrades to glutamate. Together, glutamine + glutamate are referred to as Glx.
- Asparagine and aspartate are often referred to as Asx when combined.
- Amino acids are classified as either indispensable (essential) or dispensable (nonessential)
- For humans, 9 amino acids are indispensable and 11 are dispensable.
- Though classified as dispensable, cysteine and tyrosine rely on essential amino acid precursors for their synthesis.
- Indispensable amino acids cannot be made by the body and must be obtained through the diet.
- Dispensable amino acids can be synthesized by the body.
- Conditionally dispensable amino acids, found in Table 1.2, can become essential under specific conditions, such as illness or when the body doesn't have enough precursors to make them.
- Histidine is a special case, as it is essential for infants and likely needed in small amounts by adults.
- The table "Common Amino Acids in the Body" in the provided text clearly lists the amino acids by category: indispensable, dispensable, and conditionally indispensable, with their 3-letter and 1-letter abbreviations.
- The body can synthesize all amino acids shown in Figure 1.4.
- In nutrition, a dispensable amino acid is defined as an amino acid that is not needed in the diet (not the same as lacking a proper synthesis pathway).
- Even though cysteine and tyrosine can be synthesized by the body, they rely on the degradation of indispensable amino acids as their precursors.
- Cysteine synthesis needs methionine to provide the sulfur atom.
Synthesis Pathways
- Serine can be synthesized from 3-phosphoglycerate, a product of glycolysis.
- Serine can be converted to glycine by transferring a methylene group to tetrahydrofolate (seen in Table 1.6 as a breakdown pathway, but also as a source of glycine and one-carbon units).
- Glycine can also be converted back into serine—significant reverse synthesis from glycine to serine occurs in humans.
Additional Notes
- Protein stores are the second largest energy source in the body after fats.
- Carbohydrates are stored as glycogen for short-term energy needs.
- The body can convert amino acids from broken down protein into glucose via gluconeogenesis, to supplement energy after glycogen depletion.
Protein Function
- Protein is important for many essential bodily functions such as breathing, immune function, and organ function.
- Losing more than 30% of body protein leads to muscle weakness, impaired immune function, and eventually death.
- During fasting, the body adapts to conserve protein by reducing nitrogen excretion.
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Description
This quiz covers essential and nonessential amino acids, including classifications, synthesis, and the importance of certain amino acids like histidine. Test your knowledge on the roles glutamine and asparagine play in protein metabolism and their significance in human nutrition.
