Nitrogen Metabolism/ Urea Cycle Biochemistry

  1. What is the most prevalent neurotransmitter?
  2. What does glutamate readily converts into?
  3. Glutamate has how many carbons? Aspartate?
    • 5 carbons for glutamate
    • 4 carbons for aspartate
  4. Glutaminase degrade _____ to form _____
    • Glutamine
    • Glutamate
  5. Glutamine synthetase converts ____ to ____
    • Glutamate
    • Glutamine
  6. Ornithine, citrulline and arginine are all compounds formed from ______
  7. What is the source of most of the body’s ammonia?
    Bacteria reducing N2 into ammonia
  8. True/false: half the dry weight of urine is uric acid
    False; it is urea
  9. What is the committed step of the urea cycle?
    Carbamoyl phosphate synthetase
  10. Which is the rate limiting step of the urea cycle?
    Carbamoyl phosphate synthetase
  11. What is carbamoyl phosphate important for?
    • Urea cycle
    • Pyrimidine biosynthesis
  12. True/False: energy is used to turn carbonic acid into carbamoyl phosphate
    True, two molecules of ATP
  13. True/False: ammonia released from glutamine or glutamate enter the urea cycle as carbonic acid
    False; it enters the urea cycle as carbamoyl phosphate
  14. How is pyrimidine biosynthesis come about?
    • Carbamoyl phosphate becomes carbamoyl aspartate, then dihydroorotate and orotate
    • From that it reacts with PRPP and eventually pyrimidine
  15. What are the four organs involved for nitrogen metabolism?
    • Kidneys
    • Intestine
    • Liver
    • Brain
  16. Where does N2 mostly come from?
    Intestine, mainly the bacteria
  17. Ammonia is converted to which compound when it is getting exported out of the blood?
  18. Liver ____ nitrogen and kidneys _____ them
    • Metabolize
    • Excrete
  19. Which is the inert harmless transporter to move ammonia from brain to the liver?
  20. How many ammonia can each glutamine transport?
    Two ammonia molecules
  21. What is the function of transaminase?
    Interconvert between amines and ketones
  22. What enzyme produce glutamine in the brain?
    Glutamine synthetase
  23. What enzyme produce alanine in muscle?
    Alanine transaminase
  24. Which enzymes produce ammonia in liver?
    • Glutaminase
    • Glutamate dehydrogenase
  25. Which enzymes produce ammonia in the kidneys?
    • Glutaminase
    • Glutamate dehydrogenase
  26. In which type of cells do glutamine or glutamate release nitrogen in the form of ammonia?
  27. Where does the urea cycle occurs?
  28. Which cell exports urea into blood for transport to kidneys?
  29. Where does nitrogen metabolism occur/ urea formation?
  30. True/False: kidney is where urea is made
    False; urea is made in the liver and kidney excretes it
  31. Which three urea cycle enzymes are found in the mitochondrial matrix?
    • N-acetyl glutamate synthase
    • Carbamoyl phosphate synthetease
    • Ornithine transcarbamylase
  32. Which three urea cycle enzymes are found in the cytosol?
    • Argininosuccinate synthetase
    • Argininosuccinate lyase
    • Arginase
  33. What results with loss of function mutations of N-acetylglutamate synthase?
    • Decrease ability to upregulate carbamoylphosphate synthetase
    • Leads to hperammonemia
  34. True/false: ammonia comes from glutamate/glutamine deamination
  35. Which urea cycle intermediate is formed in the cytosol and transported back to the mitochondrial matrix
  36. How many nitrogens in urea molecule and where did they come from?
    • 2
    • One from carbamoyl phosphate
    • One from arginine
  37. True/false: ornithine transcarbamylase deficiency is an X linked dominant disorder
    False; it is X linked recessive
  38. Loss of function is typically _____ mutations
  39. What are some immediate emergent treatment for hyperammonemia?
    • Dialysis
    • NG tube lactulose
  40. Why is lactulose the most widely used pharmaceuticals for hyperammonemia?
    Because bacterial will eat lactulose and will lower pH of blood, therefore ammonia has a 100 fold drop
  41. Rate of ammonia/ammonium drops ____ fold when treating it with lactulose
  42. Which enzyme moves aspartate and glutamate in and out of the mitochondria?
  43. What is the HHH syndrome?
    • Hperornithinemia-hperammonemia-homocitrullinurea
    • Loss-of-function mutation to the ornithine carrier
Card Set
Nitrogen Metabolism/ Urea Cycle Biochemistry
Renal Midterm- Biochemistry