p.13
Protein Requirement and Nitrogen Balance
What is the nitrogen balance when subjects are on a protein-free diet?
It will gradually increase until nitrogen balance is zero.
p.22
Essential and Non-Essential Amino Acids
How many essential amino acids are there?
There are 22 essential amino acids.
p.15
Protein Requirement and Nitrogen Balance
Why is metabolic control necessary in protein intake?
To adjust the rate of amino acid disposal due to variations in dietary protein intake.
p.50
Amino Acid Catabolism and Urea Cycle
Why is urea produced instead of ammonia?
Because ammonia is toxic.
p.13
Protein Requirement and Nitrogen Balance
What is the minimum intake of protein required for nitrogen equilibrium?
54 mg/kg body weight/day.
p.22
Essential and Non-Essential Amino Acids
Why is knowledge of essential amino acid requirements crucial for certain patients?
Because they rely on amino acid solutions for nutrition.
p.15
Protein Requirement and Nitrogen Balance
What are Dietary Reference Intakes (DRI) related to?
They provide guidelines for protein requirements.
p.25
Protein Requirement and Nitrogen Balance
Why do we need more protein in daily living?
Because the quality of protein in foods is not always high.
p.39
High Protein Diet and Its Effects
What is the recommended protein consumption amount for healthy adults?
1.5 to 2 times the recommended intakes.
p.15
Protein Requirement and Nitrogen Balance
What factors influence protein requirements?
Metabolic situations such as growth, pregnancy, and lactation.
p.6
Amino Acid Classification and Structure
What is the primary reason animals are unaffected by herbicides that target aromatic amino acid synthesis?
Animals lack the metabolic pathways to synthesize aromatic amino acids, unlike plants.
p.21
Protein Requirement and Nitrogen Balance
How is protein requirement established?
Based on the consumption of high-quality proteins, such as eggs.
p.27
Protein Quality Assessment Metrics
What are low-quality proteins?
Proteins that have little of one or more essential amino acids (EAA), mostly derived from plant foods like legumes, vegetables, cereals, and grains.
p.59
Amino Acid Catabolism and Urea Cycle
How is amino acid metabolism related to energy metabolism?
It is part of the essential pathways of energy metabolism.
p.10
Protein Requirement and Nitrogen Balance
What is the significance of protein requirements?
They determine the amount of protein needed for growth, maintenance, and overall health.
p.27
Protein Quality Assessment Metrics
Why might vegetarians have more incomplete proteins in their diet?
Because they primarily consume plant-based foods, which are often low in one or more essential amino acids.
p.56
Amino Acid Catabolism and Urea Cycle
Why is N-acetylglutamate important in metabolism?
N-acetylglutamate is a key activator of carbamoyl phosphate synthetase I, which initiates the urea cycle.
p.38
Protein Quality Assessment Metrics
What is the amino acid score method used for?
To determine the limiting amino acid of a food.
p.25
Protein Quality Assessment Metrics
What is protein quality?
The degree to which a food protein meets the requirement for all essential amino acids (EAA).
p.39
High Protein Diet and Its Effects
What is protein poisoning?
When the body takes in too much protein with not enough fat and carbohydrates for a long period.
p.59
Amino Acid Catabolism and Urea Cycle
When are endogenous amino acids used for energy?
When there is leftover amino acids from normal protein degradation, excess protein intake, or inadequate nutrients (e.g., starvation, diabetes).
p.42
Protein-Energy Malnutrition (PEM)
What is a symptom of kwashiorkor in children?
Depigmentation of the skin and hair.
p.57
Amino Acid Catabolism and Urea Cycle
What role do glutamate and glutamine play in amino acid metabolism?
They are central to amino acid metabolism, serving as key intermediates in various metabolic pathways.
p.42
Protein-Energy Malnutrition (PEM)
What is the biochemical basis for the depigmentation seen in kwashiorkor?
The deficiency in dietary protein leads to a lack of amino acids necessary for melanin production, resulting in lighter skin and hair color.
p.10
Essential and Non-Essential Amino Acids
What factors influence amino acid requirements?
Age, sex, health status, and physical activity level.
p.32
Protein Quality Assessment Metrics
What does a higher AA score indicate?
A higher quality of the test protein in terms of essential amino acid composition.
p.42
Protein-Energy Malnutrition (PEM)
What role do amino acids play in skin and hair pigmentation?
Amino acids are precursors for melanin, the pigment responsible for color in skin and hair.
p.25
Protein Requirement and Nitrogen Balance
How is protein requirement determined?
Based on the use of a diet that contains high-quality protein.
p.23
Protein Requirement and Nitrogen Balance
Why does the protein requirement for the elderly differ from that of adults?
Elderly individuals often experience muscle loss and require more protein to maintain muscle mass and overall health.
p.6
Amino Acid Classification and Structure
How do animals obtain aromatic amino acids?
Through their diet, as they cannot synthesize them.
p.32
Protein Quality Assessment Metrics
What does AA score measure?
The determination of essential amino acid (EAA) composition of a test protein compared to a reference protein.
p.20
Protein Requirement and Nitrogen Balance
What is one key factor to improve health and quality of life in older adults?
Maintaining high levels of muscle mass.
p.57
Amino Acid Catabolism and Urea Cycle
How does glutamate contribute to amino acid metabolism?
Glutamate acts as a key amino group donor in the synthesis of other amino acids and is involved in the urea cycle.
p.28
Protein Quality Assessment Metrics
What does PER stand for in protein quality evaluation?
Protein Efficiency Ratio.
p.56
Amino Acid Catabolism and Urea Cycle
How does arginine influence nitrogen metabolism?
Arginine serves as a substrate for the synthesis of N-acetylglutamate, thereby enhancing nitrogen metabolism.
p.45
Amino Acid Catabolism and Urea Cycle
What role does α-ketoglutarate play in amino acid metabolism?
It accepts α-amino groups from most amino acids, producing α-keto acids and glutamate.
p.13
Protein Requirement and Nitrogen Balance
What is the Factorial Method used for?
To measure obligatory nitrogen loss when the diet contains no protein.
p.13
Protein Requirement and Nitrogen Balance
What are the sources of nitrogen loss in mg N/kg body weight?
Urinary: 37, Faecal: 12, Skin: 3, Miscellaneous: 2, Total: 54.
p.39
High Protein Diet and Its Effects
Is a high protein diet harmful for chronic kidney disease patients?
Yes, it is considered harmful for them.
p.34
Protein Quality Assessment Metrics
What does PDCAAS stand for?
Protein Digestibility-Corrected Amino Acid Score.
p.50
Amino Acid Catabolism and Urea Cycle
What dietary conditions stimulate ureagenesis?
High protein diet and starvation.
p.65
Essential and Non-Essential Amino Acids
Which amino acids are classified as branched-chain amino acids (BCAAs)?
Isoleucine, leucine, and valine.
p.18
Protein Requirement and Nitrogen Balance
What is the purpose of repeated protein ingestion for athletes?
To optimize muscle mass in trained populations.
p.71
Disorders of Phenylalanine and Tyrosine Metabolism
What is the consequence of a phenylalanine hydroxylase defect?
Individuals require dietary tyrosine for normal growth.
p.20
Protein Requirement and Nitrogen Balance
What is 'anabolic resistance'?
A rightward shift in the protein dose-response curve characteristic of an inactive lifestyle, especially with aging.
p.10
Essential and Non-Essential Amino Acids
Why are amino acids essential?
They are necessary for protein synthesis and cannot be synthesized by the body.
p.58
Amino Acid Catabolism and Urea Cycle
What is ammonia used for in amino acid catabolism?
In the synthesis of urea.
p.7
Functions of Amino Acids Beyond Protein Synthesis
What role do amino acids play beyond being building blocks for proteins?
They serve as precursors for many nitrogen-containing compounds with important physiological functions.
p.44
Amino Acid Catabolism and Urea Cycle
What is the first phase of amino acid catabolism?
Removal of the α-amino groups, forming ammonia.
p.13
Protein Requirement and Nitrogen Balance
How does the nitrogen requirement from a Nitrogen Balance Study compare to the Factorial Method?
It is 30% higher due to lower retention efficiency.
p.23
Protein Requirement and Nitrogen Balance
What is the recommended protein requirement for the elderly (g per kg per day)?
1.0 to 1.2 g per kg per day.
p.65
Amino Acid Classification and Structure
What increases the uptake of amino acids in muscles?
After a meal or exercise.
p.18
Protein Requirement and Nitrogen Balance
What is the recommended frequency for protein-containing meals for athletes?
Every ~4 hours, totaling ~4 to 5 meals.
p.56
Amino Acid Catabolism and Urea Cycle
What is the role of arginine in regulating N-acetylglutamate synthase?
High levels of arginine positively regulate N-acetylglutamate synthase, which is important for the urea cycle and nitrogen metabolism.
p.42
Protein-Energy Malnutrition (PEM)
How does protein deficiency affect melanin production?
Insufficient protein intake reduces the availability of amino acids like tyrosine, which is crucial for melanin synthesis.
p.34
Protein Quality Assessment Metrics
What is a key characteristic of the protein product regarding amino acids?
It provides all the necessary amino acids.
p.66
Amino Acid Catabolism and Urea Cycle
What enzyme is responsible for the transamination of BCAAs to form α-keto acids?
BCAA aminotransferase (BCAAT).
p.56
Amino Acid Catabolism and Urea Cycle
What is the relationship between arginine and N-acetylglutamate?
Arginine stimulates the production of N-acetylglutamate, which is crucial for the regulation of the urea cycle.
p.11
Protein Requirement and Nitrogen Balance
What happens to excess amino acids in the body?
They are rapidly degraded and excreted.
p.67
Amino Acid Catabolism and Urea Cycle
In what forms does the liver receive a large quantity of NH3 from other tissues?
As glutamate and alanine.
p.17
Protein Requirement and Nitrogen Balance
Can increasing protein intake help build more muscle?
Yes, higher protein intake can support muscle building.
p.22
Protein Requirement and Nitrogen Balance
What do patients who cannot intake food orally rely on?
Liquid diets and intravenous feeding using amino acid solutions.
p.6
Amino Acid Classification and Structure
Why are herbicides that inhibit the synthesis of aromatic amino acids considered safe to use near animals?
Animals do not synthesize aromatic amino acids; they obtain them from their diet, making these herbicides non-toxic to them.
p.39
High Protein Diet and Its Effects
What is rabbit starvation?
A consequence of eating rabbit meat exclusively, leading to protein poisoning.
p.27
Protein Quality Assessment Metrics
What are high-quality proteins?
Proteins that contain all the essential amino acids (EAA) in the approximate amounts needed by humans, e.g., milk, yogurt, cheese, eggs.
p.10
Protein Requirement and Nitrogen Balance
What are the two main types of protein requirements?
Protein requirement and amino acids requirement.
p.27
Protein Requirement and Nitrogen Balance
What can result from a diet containing only low-quality proteins?
Inadequate availability of certain amino acids, inhibiting the body's ability to synthesize its own proteins.
p.32
Protein Quality Assessment Metrics
How is the AA score calculated?
AA score = (mg of amino acid in 1g test protein / mg of amino acid in 1g high-quality protein) x 100%.
p.71
Disorders of Phenylalanine and Tyrosine Metabolism
What genetic defect affects the requirement for tyrosine?
A defect in phenylalanine hydroxylase.
p.21
Protein Requirement and Nitrogen Balance
What is the difference between protein requirement and amino acid requirement?
Protein requirement refers to a large amount of protein, while amino acid requirement refers to sufficient amino acids.
p.57
Amino Acid Catabolism and Urea Cycle
What is the significance of glutamine in amino acid metabolism?
Glutamine serves as a nitrogen donor for the synthesis of nucleotides and other biomolecules, and plays a role in acid-base balance.
p.47
Amino Acid Catabolism and Urea Cycle
What is the role of glutamate dehydrogenase (GDH) in amino acid metabolism?
GDH is involved in the traffic control of amino acid disposal and synthesis of non-essential amino acids.
p.57
Amino Acid Catabolism and Urea Cycle
In what ways do glutamate and glutamine interact in metabolism?
They can be interconverted, with glutamate being converted to glutamine through the addition of an amino group, and vice versa.
p.31
Protein Quality Assessment Metrics
When are NPU and Biological Value (BV) the same?
When food proteins are completely digested.
p.53
Amino Acid Catabolism and Urea Cycle
What can cause an overload of the urea cycle?
NH4Cl consumption, increased protein degradation, or an arginine deficient diet.
p.54
Amino Acid Catabolism and Urea Cycle
What are some nitrogenous waste products that are excreted in urine alongside creatinine?
Urea, ammonia, and uric acid.
p.53
Amino Acid Catabolism and Urea Cycle
What happens when the urea cycle is overloaded?
CPS I in mitochondria cannot handle all ammonia, leading CPS II in cytosol to take over.
p.44
Amino Acid Catabolism and Urea Cycle
What occurs in the second phase of amino acid catabolism?
Conversion of α-keto acids to common intermediates of energy-producing metabolic pathways.
p.67
Functions of Amino Acids Beyond Protein Synthesis
What role do amino acids play in protein synthesis in the liver?
They are used to synthesize lipoproteins.
p.63
Amino Acid Catabolism and Urea Cycle
What role does the liver play in amino acid metabolism?
It traps gluconeogenic amino acids for glucose production.
p.24
Protein Quality Assessment Metrics
Why is amino acid composition important for protein quality?
It determines whether the protein provides all essential amino acids needed by the body.
p.13
Protein Requirement and Nitrogen Balance
What nitrogen balance is achieved when loss and gain are on a 1:1 ratio?
Equilibrium nitrogen balance.
p.29
Protein Quality Assessment Metrics
What does the Protein Efficiency Ratio (PER) represent?
Body weight gained for a specific time period on a test protein divided by the grams of protein consumed.
p.29
Protein Quality Assessment Metrics
How is PER calculated?
PER = grams weight gain / grams protein consumed.
p.54
Amino Acid Catabolism and Urea Cycle
What is the primary source of creatinine in the body?
The cyclization of creatine and phosphocreatine in muscle.
p.65
Amino Acid Metabolism and Urea Cycle
Where are branched-chain amino acids primarily metabolized?
By muscle, rather than by the liver.
p.18
Protein Requirement and Nitrogen Balance
What does the solid line represent in the meal protein distribution pattern?
Fasted muscle protein synthesis.
p.19
Protein Requirement and Nitrogen Balance
What is sarcopenia?
A disease associated with aging characterized by drastic reduction in muscle mass.
p.31
Protein Quality Assessment Metrics
What does Net Protein Utilization (NPU) measure?
The proportion of nitrogen retained in the body versus the amount of nitrogen consumed.
p.24
Protein Quality Assessment Metrics
What is protein quality?
A measure of how well a protein meets the body's amino acid requirements.
What do nitrogen balance studies evaluate?
Dietary nitrogen intake and nitrogen loss from the body.
p.35
Protein Quality Assessment Metrics
What is the purpose of understanding protein quality metrics?
To make informed decisions about protein supplements.
p.40
High Protein Diet and Its Effects
What happens when excessive amounts of protein are consumed?
It can increase levels of ammonia, urea, and amino acids in the blood.
p.33
Protein Quality Assessment Metrics
What does a PDCAAS value of 0 indicate?
The lowest protein quality.
p.40
High Protein Diet and Its Effects
What are some effects of protein poisoning?
Increased urinary nitrogen excretion, glomerular filtration rate, kidney hypertrophy, and metabolic acidosis.
p.47
Amino Acid Catabolism and Urea Cycle
What happens to amino acid degradation by GDH when energy levels are low in the cell?
Amino acid degradation by GDH is high, facilitating energy production from carbon skeletons derived from amino acids.
p.28
Protein Quality Assessment Metrics
What is the significance of evaluating protein quality?
To determine the effectiveness of protein sources for growth and maintenance.
p.35
Protein Quality Assessment Metrics
What does PER assess?
The ability of a protein to induce weight gain, including both lean and fat mass.
p.45
Amino Acid Catabolism and Urea Cycle
What type of reactions are catalyzed during amino acid catabolism?
Aminotransferase reactions using α-ketoglutarate as the amino group acceptor.
p.36
Protein Quality Assessment Metrics
What does a PDCAAS score of 1 signify?
It signifies that the protein shares excellent essential amino acids.
p.53
Amino Acid Catabolism and Urea Cycle
How can orotic aciduria be reversed?
By supplementing the diet with citrulline, ornithine, or arginine.
p.67
Amino Acid Catabolism and Urea Cycle
What is the role of ketogenic amino acids in the liver?
They are converted to acetyl CoA, which can produce acetone, acetoacetate, and β-hydroxybutyrate.
p.26
Protein Quality Assessment Metrics
What does true digestibility eliminate from the measurement?
Endogenous nitrogen in feces.
Why can't amino acids be stored in the body?
Because they are used for protein synthesis and nitrogen balance.
p.21
Protein Requirement and Nitrogen Balance
Why do we need to adjust protein requirements?
Because we do not consume just one type of protein, and we need to consider the amino acid profile of various proteins.
p.21
Protein Requirement and Nitrogen Balance
What does nitrogen balance indicate?
It does not necessarily mean amino acid balance; a person can be in nitrogen balance but have an amino acid imbalance.
p.44
Amino Acid Catabolism and Urea Cycle
What percentage of energy in the liver is derived from amino acids?
50% (for gluconeogenesis and urea cycle).
p.58
Amino Acid Catabolism and Urea Cycle
What is the first phase of amino acid catabolism?
The removal of the α-amino groups, forming ammonia.
p.11
Protein Requirement and Nitrogen Balance
How are amino acids stored in the body compared to fats and carbohydrates?
Amino acids are not stored by the body.
p.54
Amino Acid Catabolism and Urea Cycle
How does creatinine leave the muscle?
It passes across the glomerulus and is secreted by the proximal tubules of the kidneys.
p.36
Protein Quality Assessment Metrics
What does a PDCAAS score of close to 100% indicate?
It indicates that a protein will provide close to 100% of the essential amino acids (EAA), including branched-chain amino acids (BCAA).
p.29
Protein Quality Assessment Metrics
What is the primary purpose of using PER?
To determine which proteins promote weight gain.
p.24
Protein Quality Assessment Metrics
What factors influence protein quality?
Amino acid composition, digestibility, and biological value.
p.58
Amino Acid Catabolism and Urea Cycle
What are ketone bodies related to in the context of amino acid catabolism?
They are part of the metabolic pathways involved in energy production.
p.63
Amino Acid Catabolism and Urea Cycle
What happens to some dietary amino acids like glutamine?
They are metabolized in enterocytes.
p.38
Essential and Non-Essential Amino Acids
How can knowledge of limiting amino acids improve nutrition?
By guiding food combinations to ensure all essential amino acids are consumed.
p.35
Protein Quality Assessment Metrics
What is a limitation of PDCAAS?
It is restricted to essential amino acids and does not account for non-essential amino acids that may become essential in certain conditions.
p.48
Amino Acid Catabolism and Urea Cycle
What is the role of glutamate in transdeamination?
It acts as the nitrogen acceptor that is transported to the liver for deamination.
p.68
Disorders of Phenylalanine and Tyrosine Metabolism
What is Phenylalanine (Phe)?
An essential amino acid (EAA) found in all proteins and in artificial sweeteners like aspartame.
p.30
Protein Quality Assessment Metrics
What does Biological Value (BV) measure?
The amount of nitrogen retained in the body for maintenance and growth versus the amount absorbed.
p.55
Protein Quality Assessment Metrics
How does muscle mass affect urinary creatinine levels?
Higher muscle mass results in higher urinary creatinine levels.
p.48
Amino Acid Catabolism and Urea Cycle
What is the final outcome of transdeamination?
The removal of NH3 from amino acids.
p.31
Protein Quality Assessment Metrics
What does 'N0' represent in the NPU formula?
Nitrogen while subjects consume a nitrogen-free diet.
p.37
Protein Quality Assessment Metrics
What is a Limiting Amino Acid (LAA)?
The essential amino acid (EAA) present in the lowest quantity in a food.
p.69
Disorders of Phenylalanine and Tyrosine Metabolism
What are catecholamines?
Hormones such as epinephrine and norepinephrine derived from Tyrosine.
p.37
Essential and Non-Essential Amino Acids
Which essential amino acids are commonly limiting in foods?
Lysine, Methionine, Threonine, and Tryptophan.
p.69
Disorders of Phenylalanine and Tyrosine Metabolism
What is melanin?
A tissue pigment synthesized from Tyrosine.
p.16
Protein Requirement and Nitrogen Balance
What do the dotted lines represent in the nitrogen balance study?
The 95% upper and lower range for the requirement estimate.
p.71
Essential and Non-Essential Amino Acids
Why is tyrosine considered a nonessential amino acid?
Because the body can normally synthesize it from phenylalanine.
p.29
Protein Quality Assessment Metrics
What does a PER of 2.5 for casein indicate?
Rats gain 2.5 g of weight for every 1 g of casein consumed.
p.44
Amino Acid Catabolism and Urea Cycle
Which amino acids are mostly utilized in muscle?
Branched-chain amino acids (BCAAs).
p.71
Disorders of Phenylalanine and Tyrosine Metabolism
How does a defect in phenylalanine hydroxylase affect tyrosine synthesis?
It prevents the conversion of phenylalanine to tyrosine, necessitating dietary intake.
p.38
Protein Quality Assessment Metrics
How is the limiting amino acid identified using the amino acid score method?
By comparing the amino acid profile of the food to a reference protein.
p.33
Protein Quality Assessment Metrics
What does PDCAAS stand for?
Protein Digestibility - Corrected Amino Acid Score.
p.48
Amino Acid Catabolism and Urea Cycle
What is transdeamination?
The combined action of aminotransferase and GDH to remove NH3 from amino acids.
p.52
Amino Acid Catabolism and Urea Cycle
How is N-Acetylglutamate synthesized?
NAG is synthesized from acetyl-CoA and glutamate by N-acetylglutamate synthase, with arginine acting as an activator.
p.44
Amino Acid Catabolism and Urea Cycle
What is ammonia used for in amino acid catabolism?
In the synthesis of urea.
p.31
Protein Quality Assessment Metrics
What happens to NPU when foods contain much fiber?
The NPU would be lower than the Biological Value (BV).
p.52
Amino Acid Catabolism and Urea Cycle
What happens to amino acids when glucagon levels are high?
Amino acids are used to produce energy, leading to an increase in ammonia content.
p.40
High Protein Diet and Its Effects
What is protein poisoning?
A rare but potentially fatal condition caused by excessive protein intake.
p.43
Amino Acid Classification and Structure
What role do amino acids play in protein metabolism?
They are the building blocks of proteins.
p.66
Amino Acid Catabolism and Urea Cycle
What are the products of the catabolism of branched chain amino acids?
Acetyl CoA and Succinyl CoA.
p.19
Protein Requirement and Nitrogen Balance
What factors contribute to lower protein intake in older people?
Changes in appetite, dietary preferences, and potential health issues.
p.68
Disorders of Phenylalanine and Tyrosine Metabolism
What is Tyrosine (Tyr) classified as?
A non-essential amino acid (non EAA).
p.35
Protein Quality Assessment Metrics
What does BV measure?
The amount of amino acids retained inside a cell.
p.16
Protein Requirement and Nitrogen Balance
What study discusses the effect of post-exercise recovery diet on nitrogen balance?
Med Sci Sports Exerc 43:44 - 53, 2011.
p.33
Protein Quality Assessment Metrics
Why is PDCAAS commonly used?
As an indicator of protein quality.
p.35
Protein Quality Assessment Metrics
What factors affect the Biological Value (BV) of a protein?
Metabolism, amount of intake, and age.
p.46
Amino Acid Catabolism and Urea Cycle
Which enzyme catalyzes the oxidative deamination of glutamate?
Glutamate dehydrogenase (GDH).
p.26
Protein Quality Assessment Metrics
How is apparent digestibility calculated?
Apparent digestibility = (Food N - Fecal N) / Food N x 100%.
p.2
Amino Acid Classification and Structure
What is interorgan amino acid exchange?
The process by which amino acids are transferred between different organs in the body.
p.60
Amino Acid Catabolism and Urea Cycle
What do ketogenic amino acids yield?
Acetoacetate (ketone bodies) or one of its precursors (acetyl-CoA or acetoacetyl-CoA).
p.62
Amino Acid Catabolism and Urea Cycle
What creates a dependence between organs in amino acid metabolism?
Products generated from amino acids in one organ may be needed by another organ.
p.52
Amino Acid Catabolism and Urea Cycle
What is the role of N-Acetylglutamate (NAG) in the urea cycle?
NAG is an essential activator for carbamoyl phosphate synthetase I (CPS I), the rate-limiting step in the urea cycle.
p.43
Overview of Protein Metabolism
What is protein metabolism?
The process by which proteins are synthesized and broken down in the body.
p.54
Amino Acid Catabolism and Urea Cycle
What happens to creatinine after it is formed?
It is excreted in the urine with other nitrogenous waste products.
p.43
Overview of Protein Metabolism
What are the two main processes involved in protein metabolism?
Protein synthesis and protein degradation.
p.11
Protein Requirement and Nitrogen Balance
What is the nature of the protein and amino acid pool in the body?
It turns over in a constant cycle of breakdown, utilization, and replenishment.
p.24
Protein Quality Assessment Metrics
What is biological value in relation to protein?
The proportion of absorbed protein from a food that becomes incorporated into the proteins of the organism's body.
p.28
Protein Quality Assessment Metrics
What does PDCAAS stand for?
Protein Digestibility - Corrected Amino Acid Score.
p.53
Amino Acid Catabolism and Urea Cycle
What reaction does CPS II catalyze in the case of urea cycle overload?
Glutamine joins with aspartate to form orotate and pyrimidine (UMP).
p.19
Protein Requirement and Nitrogen Balance
What factors lead to higher protein needs in older people?
Increased muscle loss and changes in body composition due to aging.
p.40
High Protein Diet and Its Effects
What does increased glomerular filtration rate indicate?
It can indicate dehydration.
p.16
Protein Requirement and Nitrogen Balance
What does a negative nitrogen balance indicate?
It indicates that nitrogen intake is less than nitrogen loss.
p.33
Protein Quality Assessment Metrics
What is the formula for PDCAAS?
PDCAAS = (mg of amino acid in 1g test protein / mg of amino acid in 1g high-quality protein) x fecal true digestibility (%).
What does a negative nitrogen balance signify?
Nitrogen intake is less than nitrogen output, indicating a catabolic state.
p.55
Protein Quality Assessment Metrics
What dietary factors can increase urinary creatinine levels?
High meat intake or creatine supplementation.
p.2
Amino Acid Catabolism and Urea Cycle
What is the significance of the urea cycle in amino acid metabolism?
It is responsible for the removal of amino nitrogen from amino acids.
p.55
Protein Requirement and Nitrogen Balance
What is low serum creatinine associated with?
Increased risk of type 2 diabetes (insulin resistance).
p.3
Overview of Protein Metabolism
What is the significance of the three-dimensional structure of a polypeptide?
It determines the protein's function.
p.68
Disorders of Phenylalanine and Tyrosine Metabolism
What is the role of BH4 in the conversion of Phenylalanine to Tyrosine?
BH4 acts as a cofactor for phenylalanine hydroxylase (PAH) in the conversion process.
p.2
Protein Requirement and Nitrogen Balance
How does protein requirement change under special metabolic conditions?
It may increase or decrease depending on the specific condition.
p.4
Amino Acid Classification and Structure
What are selenoproteins?
Proteins containing selenocysteine.
p.4
Amino Acid Classification and Structure
Which amino acids have hydroxyl- or sulfur-containing side chains?
Serine, Threonine, Cysteine, Methionine.
p.4
Amino Acid Classification and Structure
List the aromatic amino acids.
Phenylalanine, Tyrosine, Tryptophan.
p.41
Protein-Energy Malnutrition (PEM)
What dietary issue contributes to Marasmus?
A bulky cereal-based diet with too few legumes and too few feedings per day.
p.10
Essential and Non-Essential Amino Acids
What is the role of non-essential amino acids?
They can be synthesized by the body and are important for various metabolic processes.
p.58
Amino Acid Catabolism and Urea Cycle
What occurs in the second phase of amino acid catabolism?
Conversion of α-keto acids to common intermediates of energy-producing metabolic pathways.
p.38
Protein Quality Assessment Metrics
What does a low amino acid score indicate?
That the food is deficient in one or more essential amino acids.
p.35
Protein Quality Assessment Metrics
What does PDCAAS measure?
The amount of the lowest essential amino acid (EAA) in the protein.
p.19
Protein Requirement and Nitrogen Balance
How does aging affect body composition?
It leads to changes in the relative weights of different compartments, such as increased fat and decreased muscle mass.
p.48
Amino Acid Catabolism and Urea Cycle
What happens if some tissues do not express GDH?
Transamination cannot get rid of NH3, leading to its transport to the liver for deamination.
p.31
Protein Quality Assessment Metrics
What is the formula for calculating NPU?
NPU = Food N – [(urine N – N0) + (fecal N – N0)] / Food N x 100%
p.45
Amino Acid Catabolism and Urea Cycle
What is the function of aspartate aminotransferase (AST)?
Transfers the amino group from glutamate to oxaloacetate, forming aspartate.
p.69
Disorders of Phenylalanine and Tyrosine Metabolism
What important substances are metabolized from Tyrosine?
Catecholamines (epinephrine and norepinephrine) and melanin.
p.31
Protein Quality Assessment Metrics
What does 'N' represent in the NPU formula?
Nitrogen while subjects consume a test protein.
p.3
Amino Acid Classification and Structure
What distinguishes D- and L-amino acids?
Their spatial arrangement around the chiral center.
p.47
Amino Acid Catabolism and Urea Cycle
How does GDH contribute to energy production?
By degrading amino acids to produce carbon skeletons that enter the TCA cycle.
p.7
Functions of Amino Acids Beyond Protein Synthesis
What is carnitine and how is it related to amino acids?
Carnitine is a nitrogen-containing compound that is synthesized from amino acids.
p.11
Protein Requirement and Nitrogen Balance
What does the daily protein synthesis imply about biological processes?
It implies that recycling is an important biological process.
p.43
Overview of Protein Metabolism
What happens during protein degradation?
Proteins are broken down into amino acids for reuse or energy.
p.62
Amino Acid Catabolism and Urea Cycle
What is an example of interorgan dependence in amino acid metabolism?
Gluconeogenesis and urea disposal.
p.2
Amino Acid Catabolism and Urea Cycle
What happens to the carbon skeleton of amino acids during metabolism?
It undergoes degradation.
p.67
High Protein Diet and Its Effects
Under what condition does lipogenesis occur in the liver?
When protein supplies a high percentage of calories.
p.64
Amino Acid Catabolism and Urea Cycle
What happens to citrulline after it is formed in the intestinal cells?
It is released into the portal vein and taken up by the liver for the urea cycle.
p.51
Amino Acid Catabolism and Urea Cycle
Where is urea generated in the body?
Only in the liver (both mitochondrial and cytosolic).
p.51
Amino Acid Catabolism and Urea Cycle
How is urea transported after its formation?
It is transported in the blood to the kidneys.
p.5
Amino Acid Classification and Structure
Which amino acids are classified as branched-chain amino acids (BCAAs)?
Valine, leucine, and isoleucine.
p.41
Protein-Energy Malnutrition (PEM)
What is Marasmus?
A condition resulting from inadequate calorie intake, with just enough albumin production due to limited amino acid use.
p.37
Protein Quality Assessment Metrics
What is the role of complementary proteins in a diet?
To enhance the overall quality of protein intake.
p.18
Protein Requirement and Nitrogen Balance
What do the dashed lines indicate in the muscle protein synthesis graph?
An optimal meal protein-induced enhancement of muscle protein synthesis.
p.66
Amino Acid Catabolism and Urea Cycle
What is the role of branch-chain α-keto acid dehydrogenase (BCKAD) in amino acid metabolism?
It catalyzes the irreversible decarboxylation of α-keto acids.
p.45
Amino Acid Catabolism and Urea Cycle
What coenzyme is required by aminotransferases for transamination?
Pyridoxal phosphate (PLP), derived from vitamin B6.
p.43
Overview of Protein Metabolism
Where does protein synthesis primarily occur?
In the ribosomes of cells.
What does it mean to be in nitrogen balance?
The amount of nitrogen consumed equals the amount excreted by the body.
p.54
Amino Acid Catabolism and Urea Cycle
Is there significant tubular reabsorption of creatinine in the kidneys?
Little or no tubular reabsorption occurs.
p.43
Protein Requirement and Nitrogen Balance
What is the significance of nitrogen balance in protein metabolism?
It indicates whether the body is gaining or losing protein.
p.24
Protein Quality Assessment Metrics
What is the significance of digestibility in protein quality?
It affects how much of the protein can be absorbed and utilized by the body.
p.40
High Protein Diet and Its Effects
What is kidney hypertrophy?
An increase in the size of the kidneys, often due to excessive protein intake.
p.61
Amino Acid Classification and Structure
What are the two types of carbon skeleton degradation?
Glucogenic and Ketogenic.
p.40
High Protein Diet and Its Effects
What is metabolic acidosis in the context of protein breakdown?
A condition that occurs when the body produces too much acid due to protein metabolism.
p.60
Amino Acid Classification and Structure
What are the seven intermediates that determine the classification of amino acids?
Oxaloacetate, pyruvate, α-ketoglutarate, fumarate, succinyl-CoA, acetyl-CoA, acetoacetate.
p.55
Protein Requirement and Nitrogen Balance
How does exercise affect insulin sensitivity?
Exercise can increase insulin sensitivity.
p.51
Amino Acid Catabolism and Urea Cycle
What are the two nitrogen sources for the Urea Cycle?
Aspartate and other amino acids (mostly glutamate).
p.26
Protein Quality Assessment Metrics
What is the formula for true digestibility?
True digestibility = (Food N - (Fecal N - N0)) / Food N x 100%.
p.70
Disorders of Phenylalanine and Tyrosine Metabolism
What causes hyperphenylalanemia (HPA)?
Dysfunctional conversion of phenylalanine (Phe) to tyrosine (Tyr), leading to elevated serum Phe and its metabolites.
p.46
Amino Acid Catabolism and Urea Cycle
What can glutamate be used for after oxidative deamination?
As an amino group donor in the synthesis of nonessential amino acids (reductive amination).
p.46
Amino Acid Catabolism and Urea Cycle
What coenzymes can GDH use during its reactions?
NAD+ for oxidative deamination and NADPH for reductive amination.
p.49
Amino Acid Catabolism and Urea Cycle
How is alanine formed in muscle?
By the transamination of pyruvate.
p.41
Protein-Energy Malnutrition (PEM)
What is Kwashiorkor?
A form of protein malnutrition with adequate energy consumption but insufficient albumin production, causing edema.
p.4
Amino Acid Classification and Structure
What are the basic amino acids?
Lysine, Arginine, Histidine.
p.61
Essential and Non-Essential Amino Acids
Which amino acid is both essential and nonessential?
Threonine (essential) and Arginine (nonessential).
p.72
Essential and Non-Essential Amino Acids
What are the special dietary amino acid requirements in different statuses?
Certain conditions like pregnancy, illness, or growth spurts may increase amino acid needs.
p.19
Protein Requirement and Nitrogen Balance
What are the consequences of sarcopenia?
Increased fat, progressive loss of muscle mass, decreased function and strength, affecting balance and daily living tasks.
p.7
Functions of Amino Acids Beyond Protein Synthesis
Name a few nitrogen-containing compounds derived from amino acids.
Purines, pyrimidines, hormones (like thyroxine), neurotransmitters (like serotonin), carnitine, and creatine.
p.36
Protein Quality Assessment Metrics
What does a low Biological Value (BV) indicate?
It indicates that not all amino acids absorbed or ingested will be efficiently used by the body.
p.3
Amino Acid Classification and Structure
What are the two functional groups present in an amino acid?
A carboxyl group (-COOH) and an amino group (-NH2).
p.69
Disorders of Phenylalanine and Tyrosine Metabolism
What are the two types of metabolism that Phenylalanine (Phe) and Tyrosine (Tyr) are involved in?
They are partially glucogenic and ketogenic.
p.38
Protein Quality Assessment Metrics
What is the significance of improving amino acid profiles in diets?
It enhances overall protein quality and nutritional value.
p.52
Amino Acid Catabolism and Urea Cycle
How does the urea cycle respond to high glucagon levels?
The urea cycle is activated to increase the rate of ammonia removal.
p.33
Protein Quality Assessment Metrics
How is the PDCAAS calculated?
By correcting the amino acid score by the digestibility of the protein.
p.53
Amino Acid Catabolism and Urea Cycle
What condition can result from the accumulation of orotate?
Orotic aciduria (excess orotate in urine).
p.69
Disorders of Phenylalanine and Tyrosine Metabolism
What is synthesized from Tyrosine in the body?
Catecholamines and melanin.
p.30
Protein Quality Assessment Metrics
What is the BV of eggs?
100%, meaning 100% of the nitrogen absorbed from egg protein is retained.
p.62
Amino Acid Catabolism and Urea Cycle
What determines the preference of amino acid metabolism in tissues?
Each tissue has its own preference for amino acid metabolism.
p.30
Protein Quality Assessment Metrics
What factors does BV take into account?
The digestibility of food proteins.
p.16
Protein Requirement and Nitrogen Balance
What does the solid line represent in the nitrogen balance study?
Predicted dietary nitrogen intake.
p.35
Protein Quality Assessment Metrics
How does protein concentration in the diet affect its utilization?
Utilization of a protein (the % retained) falls with increasing concentration in the diet.
p.41
Protein-Energy Malnutrition (PEM)
What is Protein-Energy Malnutrition (PEM)?
A macronutrient deficiency disease resulting from inadequate intake and/or utilization of protein and calories.
p.49
Amino Acid Catabolism and Urea Cycle
What does glutaminase produce when it cleaves glutamine?
Glutamate and free ammonia.
p.60
Amino Acid Classification and Structure
Which amino acids are classified as glucogenic?
Asparagine, glutamate, alanine, phenylalanine, methionine, aspartate, glutamine, serine, tyrosine, valine, lysine, arginine, glycine, isoleucine, histidine, cysteine, threonine, tryptophan, proline.
p.41
Protein-Energy Malnutrition (PEM)
What are the risks associated with PEM?
Higher risk of parasitic and infectious diseases that reduce appetite, absorption, and nutrient utilization.
p.4
Amino Acid Classification and Structure
Name four amino acids with aliphatic side chains.
Glycine, Alanine, Valine, Leucine, Isoleucine.
p.2
Protein Requirement and Nitrogen Balance
What are the outcomes of high protein intake?
Can lead to increased nitrogen excretion and potential strain on kidneys.
p.46
Amino Acid Catabolism and Urea Cycle
What are the combined actions of aminotransferase and glutamate dehydrogenase involved in?
The removal of nitrogen from amino acids.
p.51
Amino Acid Catabolism and Urea Cycle
What is the first nitrogen source in the Urea Cycle?
The first nitrogen source is from carbamoyl phosphate (CPS I).
What factors influence nitrogen balance?
Metabolic and physical status (e.g., infant, adult, bodybuilder).
p.45
Amino Acid Catabolism and Urea Cycle
What does alanine aminotransferase (ALT) do?
Transfers the amino group of alanine to α-ketoglutarate, forming pyruvate and glutamate.
p.66
Amino Acid Catabolism and Urea Cycle
Which three branched chain amino acids are involved in catabolic pathways?
Valine, isoleucine, and leucine.
p.36
Protein Quality Assessment Metrics
What is the significance of branched-chain amino acids (BCAA) in protein synthesis?
BCAAs are known to have the greatest effect on protein synthesis.
What is indicated by a positive nitrogen balance?
Nitrogen intake is greater than nitrogen output, indicating an anabolic state.
p.14
Protein Requirement and Nitrogen Balance
How do you calculate protein content from nitrogen?
Protein (g) = Nitrogen (g) x 6.25.
p.60
Amino Acid Classification and Structure
How are amino acids classified based on their degradation products?
As glucogenic, ketogenic, or both.
p.19
Protein Requirement and Nitrogen Balance
What happens to muscle and fat composition from age 25 to 65?
There is a progressive loss of muscle and an increase in fat.
p.7
Functions of Amino Acids Beyond Protein Synthesis
What is creatine and its relation to amino acids?
Creatine is a nitrogen-containing compound that is derived from amino acids.
p.48
Amino Acid Catabolism and Urea Cycle
What two processes combine to form transdeamination?
Transamination and deamination.
p.68
Disorders of Phenylalanine and Tyrosine Metabolism
What enzyme catalyzes the conversion of L-phenylalanine to L-tyrosine?
Phenylalanine hydroxylase (PAH).
p.60
Amino Acid Catabolism and Urea Cycle
What do glucogenic amino acids yield?
Pyruvate or one of the intermediates of the TCA cycle.
p.62
Amino Acid Catabolism and Urea Cycle
What processes in the liver utilize amino acids transferred from muscle proteolysis?
Urea synthesis and gluconeogenesis.
p.30
Protein Quality Assessment Metrics
How is Biological Value (BV) calculated?
BV = Food N - [(urine N - N0) + (fecal N - N0)] / (Food N - (fecal N - N0)) x 100%.
p.68
Disorders of Phenylalanine and Tyrosine Metabolism
What is aspartame?
An artificial sweetener that contains Phenylalanine.
p.72
Functions of Amino Acids Beyond Protein Synthesis
How can amino acids be used as an energy source?
Amino acids can be converted into glucose or fatty acids through metabolic pathways.
p.5
Essential and Non-Essential Amino Acids
What are conditional-essential amino acids?
Amino acids whose synthesis depends on dietary supply or the organism's biosynthesis capacity.
p.70
Disorders of Phenylalanine and Tyrosine Metabolism
How is the severity of PKU reflected?
By serum Phe levels: Classic PKU (>20 mg/dL), Mild PKU (10-20 mg/dL), Non-PKU (3.5-10 mg/dL), Normal individual (1 mg/dL).
p.61
Essential and Non-Essential Amino Acids
What is the classification of Phenylalanine?
Essential and glucogenic.
p.72
Disorders of Phenylalanine and Tyrosine Metabolism
What are the consequences of defective amino acid metabolism?
It can lead to metabolic disorders and accumulation of toxic metabolites.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What are the functions of Glycine?
It is a precursor in purine biosynthesis, for glutathione and creatine, and acts as a neurotransmitter.
p.72
Protein-Energy Malnutrition (PEM)
What happens if protein intake is deficient?
It can result in muscle wasting, immune dysfunction, and other health issues.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What does Phenylalanine convert into?
It is a precursor of tyrosine, and via tyrosine, it is a precursor of catecholamines, DOPA, and melanin.
p.2
Overview of Protein Metabolism
What are the main topics covered in the lecture on amino acids?
Amino acids, protein requirement, protein quality, protein/ amino acid metabolism, removal of amino nitrogen and urea cycle, degradation of the carbon skeleton of amino acids, interorgan amino acid exchange, protein requirement under special metabolic conditions, and outcomes of low and high protein intake.
p.64
Amino Acid Catabolism and Urea Cycle
What is the fate of glutamate (Glu) in enterocytes?
It is transaminated with pyruvate to form α-ketoglutarate and alanine.
p.3
Functions of Amino Acids Beyond Protein Synthesis
How do amino acids contribute to pH balance in cells?
They buffer the H+ concentration within cells.
p.68
Disorders of Phenylalanine and Tyrosine Metabolism
How is Tyrosine formed in the body?
By the hydroxylation of Phenylalanine in the liver by phenylalanine hydroxylase (PAH) when dietary intake of Tyr is low.
p.4
Amino Acid Classification and Structure
How many proteinogenic amino acids are there?
21 proteinogenic amino acids.
p.49
Amino Acid Catabolism and Urea Cycle
What is the role of glutamine in ammonia transport?
It is a nontoxic form of ammonia transported in the blood to the liver.
p.63
Overview of Protein Metabolism
What is the significance of postprandial amino acid exchange between organs?
It facilitates the distribution and utilization of amino acids for various metabolic processes.
p.3
Amino Acid Classification and Structure
How can amino acids be classified?
Based on their functional group (R), polarity, or spatial arrangement.
p.72
Protein Quality Assessment Metrics
How can protein quality be determined?
By assessing various metrics such as amino acid composition and digestibility.
p.2
Protein-Energy Malnutrition (PEM)
What are the outcomes of low protein intake?
Can lead to protein-energy malnutrition and various health issues.
p.41
Protein-Energy Malnutrition (PEM)
What is the protein content of maize and beans when combined?
Maize has ~10% protein and beans have ~22% protein.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What is the function of Alanine in amino acid metabolism?
It acts as a nitrogen carrier from peripheral tissues to the liver for nitrogen excretion.
p.51
Amino Acid Catabolism and Urea Cycle
What happens to urea in the kidneys?
It passes into the glomerular filtrate and is excreted in the urine.
p.61
Amino Acid Classification and Structure
Which amino acids are classified as branched-chain?
Isoleucine, Leucine, and Valine.
p.51
Amino Acid Catabolism and Urea Cycle
What enzyme converts ornithine and carbamoyl phosphate in the Urea Cycle?
Ornithine transcarbamoylase.
p.5
Disorders of Phenylalanine and Tyrosine Metabolism
What can impair the metabolism of phenylalanine and methionine?
Immature liver function or liver disease.
p.4
Amino Acid Classification and Structure
Name the acidic amino acids and their amides.
Asparagine, Glutamine, Aspartate, Glutamate.
p.5
Essential and Non-Essential Amino Acids
What are essential amino acids (EAAs)?
Amino acids that cannot be synthesized in the body and make up 20% of total dietary amino acid intake.
p.37
Protein Quality Assessment Metrics
What are complementary proteins?
Food groups that can complement each other to increase overall protein quality.
p.26
Protein Quality Assessment Metrics
What does N0 represent in the context of true digestibility?
Nitrogen while subjects consume a nitrogen-free diet.
p.70
Disorders of Phenylalanine and Tyrosine Metabolism
What is phenylketonuria (PKU)?
A disorder that always causes hyperphenylalanemia (HPA), but not all cases of HPA are PKU.
p.72
Amino Acid Catabolism and Urea Cycle
How is extra nitrogen eliminated from different tissues?
Through the urea cycle and excretion via urine.
p.72
Amino Acid Catabolism and Urea Cycle
What occurs during the fasting phase regarding amino acid metabolism?
Amino acids are released from muscle tissue and used for energy and gluconeogenesis.
p.51
Amino Acid Catabolism and Urea Cycle
What is the role of argininosuccinate synthetase in the Urea Cycle?
It catalyzes the formation of argininosuccinate from citrulline and aspartate.
p.72
Protein Requirement and Nitrogen Balance
What are the outcomes of excess protein intake?
It can lead to increased nitrogen excretion and potential kidney strain.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What are the roles of Serine in the body?
It is a constituent of phospholipids and a precursor of sphingolipids, ethanolamine, and choline.
p.5
Essential and Non-Essential Amino Acids
What are non-essential amino acids (NEAAs)?
Amino acids that can be synthesized from common intermediates in metabolism.
p.64
Functions of Amino Acids Beyond Protein Synthesis
What role does glutamine play in intestinal cells?
It prevents atrophy of the intestinal cells.
p.30
Protein Quality Assessment Metrics
What does 'N0' represent in the BV calculation?
Nitrogen while subjects consume a nitrogen-free diet.
p.72
Functions of Amino Acids Beyond Protein Synthesis
What happens to dietary amino acids during the absorptive phase?
They are absorbed and utilized for protein synthesis and energy.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What role does Aspartate play in the body?
It is involved in urea biosynthesis and acts as a pyrimidine precursor.
p.5
Essential and Non-Essential Amino Acids
Which amino acids are considered non-essential?
Cysteine, glutamate, glycine, proline, alanine, asparagine, aspartate, and serine.
p.5
Essential and Non-Essential Amino Acids
List three essential amino acids.
Methionine, phenylalanine, and tryptophan.
p.51
Amino Acid Catabolism and Urea Cycle
What is the final step of the Urea Cycle?
Arginase catalyzes the conversion of arginine to urea and ornithine.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What is the function of Methionine in amino acid metabolism?
It serves as a methyl group donor for many synthetic processes and is a precursor of cysteine.
p.62
Amino Acid Catabolism and Urea Cycle
What is the typical pattern of amino acid metabolism?
It varies in different tissues.
p.64
Protein-Energy Malnutrition (PEM)
Why might glutamine be considered a potential nutrient supplement for immature infants?
Because it prevents atrophy of the intestinal cells.
p.60
Amino Acid Classification and Structure
What is the significance of branched-chain amino acids in metabolism?
They are essential amino acids that can be both glucogenic and ketogenic.
p.5
Essential and Non-Essential Amino Acids
What is the role of methionine in amino acid classification?
It is classified as an essential amino acid.
p.41
Protein-Energy Malnutrition (PEM)
What is a common cause of Kwashiorkor in infants?
Weaning onto sugar water (0% protein) or cassava (2% protein).
p.8
Functions of Amino Acids Beyond Protein Synthesis
What is Tryptophan a precursor of?
It is a precursor of serotonin and nicotinamide (a B-vitamin).
p.8
Functions of Amino Acids Beyond Protein Synthesis
What is Cysteine a precursor for?
It is a precursor of taurine, used in bile acid conjugation, and part of glutathione.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What is Glutamate's role in amino acid metabolism?
It serves as an intermediate in amino acid interconversion and is a precursor of proline, ornithine, and arginine; it is also a source of ammonia.
p.51
Amino Acid Catabolism and Urea Cycle
What does argininosuccinate lyase do in the Urea Cycle?
It cleaves argininosuccinate into arginine and fumarate.
p.8
Functions of Amino Acids Beyond Protein Synthesis
How does Glutamine function in the body?
It acts as an amino group donor to non-amino acid reactions, is a nitrogen carrier, and a source of ammonia.
p.5
Essential and Non-Essential Amino Acids
What is the significance of arginine in amino acid classification?
It is classified as a conditional-essential amino acid.
p.70
Disorders of Phenylalanine and Tyrosine Metabolism
What alternative pathways exist for the catabolism of phenylalanine in PKU?
Alternative pathways for catabolism are utilized due to the dysfunctional conversion of Phe to Tyr.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What role does Lysine play in protein metabolism?
It is involved in cross-linking proteins (as in collagen) and is a precursor of carnitine biosynthesis, which is used in fatty acid transport.
p.8
Functions of Amino Acids Beyond Protein Synthesis
What is Histidine a precursor of?
It is a precursor of histamine.
