Medical Biochemistry: Nitrogenous Waste Flashcards
What is the 4 nitrogenous compounds found in urine
Urea
Uric acid
Creatinine
NH4+ (ammonium)
Why is urea in urine
Reduce ammonia in plasma that is toxic
What is the 2 ways in which NH3 reaches the liver
- Glutamine synthetase system
- Glucose alanine system
What is a transaminase reaction
Transfer of nitrogen-amine group
What is required for transaminase to occur
PLP an active form of B6
What is deamination
N-Amie group is removed & AA is used for energy & ammonia is converted to urea & excreted
Why is NH4+ toxic
It ca cross the BBB & utilize a-ketoglutarate & deplete leaving the brain w/ no ATP production
What is the glucose-alanine cycle
At skeletal muscle NH3+a-ketoglutarate gets converted to glutamate
Glutamate + pyruvate gives alanine + a-ketoglutarate
Alanine get transported to the liver via blood & converted to glutamine then NH4+ & urea
What is glutamate synthetase
Glutamate gets converted to glutamine in tissue & transported to the liver
At the liver glutamine gets converted to glutamate + NH4+ & converted to urea
What is the main function of NH4+ in the urine
To act as a buffer & spare bicarbonate during acidosis so that it can act as a buffer in the blood
Where does urinary NH4+ come from
Glutamine metabolism
From what is uric A in urine formed from
Purine degradation
What important enzymes catalyses uric acid production
Xanthine oxidase
What is uric acid form at physiological pH & what is the consequences
Ionized form that is poorly soluble & increase [ ] can lead to uric acid crystals that deposit at synovial joint resulting in gout at the big toe
What is the treatment for high uric acid [ ]
Diet changes & medication that is similar to xanthine oxidase & inhibits uric acid formation
