protein metabolism

• What is the total supply of free amino acids in the human body called?

  Amino Acid Pool
• What are the sources of amino acids in the body?

  Dietary protein and protein turnover
• What does negative nitrogen balance indicate?

  Degradation exceeds synthesis, leading to tissue wasting
• What is positive nitrogen balance associated with?

  Synthesis exceeds degradation, indicating growth
• What percentage of free amino acids is used for protein synthesis?

  75%
• What are the fates of excess amino acids?

  Degraded for energy or converted to metabolic substances
• What can the carbon skeleton of amino acids be converted into?

  Pyruvate, Acetyl CoA, or TCA cycle intermediates
• What is transamination?

  Interchange of amino and keto groups between acids
• What enzyme is involved in transamination?

  Aminotransferase
• What vitamin is required for transamination?

  Pyridoxine (Vitamin B6)
• What are the two commonly encountered keto acids?

  Pyruvate and Oxaloacetate
• What is the most important transamination reaction?

  Glutamate production from α-ketoglutarate
• What amino acid is produced from the transamination of α-ketoglutarate?

  Glutamate
• What is the second transamination reaction that occurs after glutamate production?

  Formation of Aspartate
• What is produced via oxidative deamination?

  NH4+
• Where does NH4+ production via oxidative deamination occur?

  Liver and Kidney mitochondria
• What enzyme is responsible for oxidative deamination?

  Glutamate Dehydrogenase
• What is the end product of the urea cycle?

  Urea
• What is the first step of the urea cycle?

  Conversion of ammonium to carbamoyl phosphate
• What is required to form carbamoyl phosphate?

  2 ATPs, CO2, and H2O
• What enzyme catalyzes the transfer of the carbamoyl group?

  Ornithine transcarbamylase
• What happens during the citrulline-aspartate condensation?

  ATP is expended to drive the reaction
• What is produced from the cleavage of argininosuccinate?

  Arginine and Fumarate
• What is the final product of arginine hydrolysis?

  Urea and Ornithine
• What condition results from excess ammonium?

  Hyperammonemia
• What is a treatment for hyperammonemia?

  Limit protein in the diet
• What happens to amino acid carbon skeletons?

  Each has a different degradation pathway
• How many metabolic products do the 20 degradation pathways converge into?

  7 metabolic products
• Which amino acids are classified as ketogenic?

  Leucine and Lysine
• What is the source of nonessential amino acids?

  They can be synthesized by the body
• What metabolic pathways are involved in the biosynthesis of nonessential amino acids?

  Glycolysis and Transamination
• What happens to heme during degradation?

  Iron is stored and carbon skeleton metabolized
• What are the steps of the urea cycle?

  1. Carbamoyl group transfer
  2. Citrulline-Aspartate condensation
  3. Argininosuccinate cleavage
  4. Urea from arginine hydrolysis
• What are the fates of amino acid degradation products?

  • Carbon skeletons converted to metabolic intermediates
  • Nitrogen portion excreted as urea
• What are the strengths and weaknesses of amino acid metabolism?

  Strengths:

  • Provides energy
  • Supports protein synthesis
  • Maintains nitrogen balance

  
  

  Weaknesses:

  • Excess can lead to hyperammonemia
  • Requires complex regulation
• What is the significance of nitrogen balance in protein metabolism?

  • Indicates overall protein status
  • Reflects tissue health and growth