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Questions and Answers
Which amino acid cannot be synthesized by the animal organism at a speed commensurate with the demands for normal growth?
Which amino acid cannot be synthesized by the animal organism at a speed commensurate with the demands for normal growth?
- Arginine
- Leucine
- Lysine (correct)
- Alanine
Which amino acid can be produced by its keto acid as long as there is an amino group that can have an amino group transfer to it from another molecule?
Which amino acid can be produced by its keto acid as long as there is an amino group that can have an amino group transfer to it from another molecule?
- Phenylalanine
- Arginine
- Leucine (correct)
- Methionine
Which amino acid can be synthesized if there is extra citrulline in the body, although it is rare in the diet?
Which amino acid can be synthesized if there is extra citrulline in the body, although it is rare in the diet?
- Arginine (correct)
- Leucine
- Isoleucine
- Valine
Which amino acid is considered nutritionally indispensable according to the metabolic sense, i.e., with appropriate precursors available?
Which amino acid is considered nutritionally indispensable according to the metabolic sense, i.e., with appropriate precursors available?
What is used to assess CO2 production?
What is used to assess CO2 production?
What represents a single point on a dose-response curve?
What represents a single point on a dose-response curve?
What should be studied at ≥6 test amino acid intake levels above and below requirement?
What should be studied at ≥6 test amino acid intake levels above and below requirement?
What is the recommended dietary allowance (RDA) for lysine intake estimated to be?
What is the recommended dietary allowance (RDA) for lysine intake estimated to be?
What percentage of the amino acid intake must indispensable amino acids in protein account for?
What percentage of the amino acid intake must indispensable amino acids in protein account for?
What are complementary proteins important for achieving?
What are complementary proteins important for achieving?
What was previously thought about the requirement for histidine?
What was previously thought about the requirement for histidine?
What did a study on histidine depletion show no effect on?
What did a study on histidine depletion show no effect on?
What may long-term histidine depletion lead to?
What may long-term histidine depletion lead to?
What did the DRI Report state about additional dietary protein for healthy adults undertaking resistance or endurance exercise?
What did the DRI Report state about additional dietary protein for healthy adults undertaking resistance or endurance exercise?
Explain the difference between dietary essentiality and metabolic essentiality in the context of essential nutrients.
Explain the difference between dietary essentiality and metabolic essentiality in the context of essential nutrients.
Discuss the significance of amino acids such as LYS, THR, and TRP in relation to their synthesis and dietary indispensability.
Discuss the significance of amino acids such as LYS, THR, and TRP in relation to their synthesis and dietary indispensability.
Explain the experimental approach used to determine amino acid essentiality in vivo, as described in the provided text.
Explain the experimental approach used to determine amino acid essentiality in vivo, as described in the provided text.
What is the recommended dietary allowance (RDA) for lysine intake estimated to be?
What is the recommended dietary allowance (RDA) for lysine intake estimated to be?
What is the estimated average requirement (EAR) for lysine intake?
What is the estimated average requirement (EAR) for lysine intake?
What percentage of the amino acid intake must indispensable amino acids in protein account for?
What percentage of the amino acid intake must indispensable amino acids in protein account for?
What are complementary proteins important for achieving?
What are complementary proteins important for achieving?
What was previously thought about the requirement for histidine?
What was previously thought about the requirement for histidine?
What did a study on histidine depletion show no effect on?
What did a study on histidine depletion show no effect on?
What may long-term histidine depletion lead to?
What may long-term histidine depletion lead to?
What did the DRI Report state about additional dietary protein for healthy adults undertaking resistance or endurance exercise?
What did the DRI Report state about additional dietary protein for healthy adults undertaking resistance or endurance exercise?
What did the report state about requirements for pregnancy and lactation?
What did the report state about requirements for pregnancy and lactation?
What techniques are used to assess CO2 production according to the text?
What techniques are used to assess CO2 production according to the text?
What is the inflection point on a dose-response curve used to represent?
What is the inflection point on a dose-response curve used to represent?
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Study Notes
Protein and Amino Acid Requirements in Human Nutrition
- Protein and amino acid requirements have been re-evaluated using advanced statistical methods and data curves
- The recommended dietary allowance (RDA) for lysine intake is estimated to be 38 mg/kg/d, with the estimated average requirement (EAR) at 31 mg/kg/d
- Indispensable amino acids in protein must account for 25% of the amino acid intake, and the protein quality need not be extremely high
- Complementary proteins, such as beans and rice or legumes and grains, are important for achieving a complete protein intake
- The Joint FAO/WHO/UNU Expert Consultation on Protein and Amino Acid Requirements in Human Nutrition (2007) provided updated amino acid requirements, with EAR estimates ranging from 3 to 14 mg/kg/d
- The requirement for histidine was previously thought to be essential only for children, but it is now known to be essential for both adults and children
- A study on histidine depletion showed no effect on nitrogen balance, suggesting it may not be essential, but it affects protein turnover and phenylalanine oxidation
- Long-term histidine depletion may lead to anemia, and low histidine rather than low iron could be the cause
- The phase of the menstrual cycle can affect lysine requirements in healthy women
- The DRI Report noted that separate requirements for women versus men, or for older adults and the elderly, could not be determined for lysine and other amino acids
- No separate requirements were determined for pregnancy and lactation, and data for children and infants were based on factorial analysis and breast milk intake
- The report also stated that no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise, and further studies are needed for various age groups and physiological conditions.
Metabolic Flux and Amino Acid Requirements
- Chicken synthesizes protein from algal protein
- Egg protein synthesis and turnover in liver is higher than in muscle
- Increase in proportion of egg protein containing phenylalanine from algal protein
- Glutamate is extensively metabolized and not phenylalanine
- Amino acid requirement represents a single point on a dose-response curve
- Phenylalanine growth increases when low
- Various measures of organ or system function are used to assess optimal dietary protein and amino acid consumption
- Subjects should be studied at ≥6 test amino acid intake levels above and below requirement
- Breath collection, isotope ratio mass spectrometry, and calorimeter used to assess CO2 production
- Measuring phenylalanine depending on lysine intake
- Different techniques give the same answer: inflection point is the requirement
- Ethical, compliance, statistical, and technological issues must be considered
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