The Many Fates of Nitrogen: Part 1 & Part 2

Flashcards covering essential concepts of nitrogen metabolism, protein digestion, and related disorders, based on the provided lecture notes.

What is nitrogen balance?

The relationship between nitrogen intake and nitrogen excretion, indicating overall protein status.

What are essential amino acids?

Amino acids that cannot be synthesized by the body and must be obtained from the diet.

Name two conditions associated with negative nitrogen balance.

Kwashiorkor and Marasmus.

What does urea represent in nitrogen metabolism?

The primary method of nitrogen excretion.

Which amino acids are classified as glucogenic?

Amino acids that can be converted into glucose.

What is the function of proteases?

Enzymes that break down proteins into peptides and amino acids.

Which hormone stimulates the release of gastrin?

Gastrin is stimulated by the presence of food in the stomach.

What is the role of trypsin in protein digestion?

It cleaves peptide bonds at lysine and arginine residues.

Define Kwashiorkor.

A form of severe protein-energy malnutrition characterized by protein deficiency despite adequate caloric intake.

What is the typical dietary protein intake recommended for adults?

100 g/day.

What triggers the ubiquitin-proteasome degradation pathway?

Short-lived or damaged proteins are tagged for degradation.

Describe the importance of vitamin B6 in amino acid metabolism.

It is a coenzyme for transaminases involved in amino acid metabolism.

What are zymogens?

Inactive enzyme precursors that become active after undergoing a biochemical change.

What is hyperammonemia?

A condition characterized by elevated levels of ammonia in the blood, often due to urea cycle disorders.

What is the role of aspartate in the urea cycle?

Aspartate donates a nitrogen atom to urea during the cycle.

How does the body regulate blood glucose levels during fasting?

Through gluconeogenesis and protein catabolism.

What does the term 'aminotransferase' refer to?

Enzymes that facilitate the transfer of amino groups between amino acids and alpha-keto acids.

What is the primary nitrogenous waste product?

Urea.

Identify the two fates of amino acids in metabolism.

They can be used for protein synthesis or catabolized for energy.

What dietary sources are recommended to meet the protein needs of children in growth phases?

Increased protein intake from sources like eggs, lean meats, and legumes.

What is the significance of branched-chain amino acids?

They are essential for muscle metabolism and energy production, especially during exercise.

Explain the correlation between urea cycle disorders and the central nervous system.

They can lead to neurological symptoms due to the accumulation of toxins like ammonia.

What are the clinical signs of Marasmus?

Severe malnutrition characterized by weight loss and muscle wasting.

How does the urea cycle contribute to nitrogen metabolism?

It converts excess nitrogen from amino acid catabolism into urea for excretion.

Define the term 'glucogenic amino acids.'

Amino acids that can be converted into intermediates of the gluconeogenesis pathway.

What happens during oxidative deamination?

The removal of an amino group from an amino acid, generating ammonia.

List examples of ketogenic amino acids.

Leucine and lysine are classified as ketogenic.

What is the effect of insulin on amino acid metabolism?

Insulin promotes the uptake of amino acids into cells and stimulates protein synthesis.

Name the two enzymes involved in the conversion of glutamate to alpha-ketoglutarate.

Glutamate dehydrogenase and transaminase.

What is the main metabolic fate of excess nitrogen in the body?

Excretion as urea.

Describe cystinuria.

An inherited condition characterized by impaired reabsorption of cystine, leading to kidney stones.

What role do hormones like CCK and secretin play in digestion?

They stimulate the secretion of digestive enzymes and bicarbonate, respectively.

Explain the process of transamination.

The transfer of an amino group from one amino acid to a keto acid, forming a new amino acid.

What is the principle behind dietary protein adequacy?

Dietary intake should match protein breakdown and synthesis to maintain nitrogen balance.

What are the consequences of arginine deficiency in the urea cycle?

Disruption of nitrogen excretion, potentially leading to elevated blood ammonia levels.

Identify the main sources of protein turnover.

Dietary proteins and body's own protein reserves.

What happens in the proteasome system?

Ubiquitin-tagged proteins are degraded into their constituent amino acids.

Which mechanisms are involved in protein turnover?

Synthesis and degradation of proteins occur simultaneously.

What are the impacts of kwashiorkor on growth?

Children with kwashiorkor experience stunted growth and muscle wasting.

Summarize the role of hydrolases in protein digestion.

Hydrolases catalyze the breakdown of proteins into smaller peptides and amino acids.

What is the link between amino acid metabolism and energy production?

Catabolized amino acids contribute to TCA cycle intermediates for ATP generation.

Define the amino acid pool.

A collection of free amino acids available for protein synthesis and energy production.

What is the significance of the enzyme CPS I in the urea cycle?

It is the rate-limiting enzyme that initiates the urea cycle.

What does the term hyperphenylalaninemia refer to?

Elevated phenylalanine levels due to impaired metabolism, notably in PKU.

Explain the relationship between diet and amino acid deficiency diseases.

Dietary imbalances lead to deficiencies in specific amino acids, causing various diseases.

What is unique about cysteine compared to other amino acids?

Cysteine contains a sulfur atom and can form disulfide bonds.

Describe the effects of nitrogen balance during pregnancy.

Pregnancy typically results in a positive nitrogen balance due to increased protein needs.

What characterizes maple syrup urine disease?

Impaired metabolism of branched-chain amino acids leading to toxic accumulation.

What do alanine and glutamine transport in the body?

They transport ammonia from peripheral tissues to the liver.

How does protein malnutrition manifest in adults?

Through muscle wasting, weakness, and decreased immunity.

What is the main biochemical role of glutamate?

It acts as a neurotransmitter and participates in nitrogen metabolism.

How does increasing dietary protein affect nitrogen balance in athletes?

Higher protein intake can support muscle synthesis and recovery in athletes.

List some techniques used in proteomics.

Mass spectrometry and protein sequencing for analysis of protein expression.

How can protein-energy malnutrition affect cognitive development?

Malnutrition can impair brain development and function in children.

What does the term 'lactate cycle' refer to in amino acid metabolism?

A cycle involving the conversion of lactate back to glucose in the liver.

Explain the significance of the kidneys in nitrogen metabolism.

The kidneys filter and excrete urea and other nitrogenous wastes from the blood.

Define oxidative deamination and its impact on amino acids.

A process that converts amino acids to keto acids while releasing ammonia.

What is the role of the pancreas in digestion?

It secretes digestive enzymes that break down proteins in the small intestine.

What do the terms 'gain of function' and 'loss of function' refer to in metabolism?

Changes in enzyme activity that either enhance or impair metabolic processes.