Nitrogen 2 Flashcards
Through what amino acid is nitrogen removed from the body?
glutamate
What do humans excrete nitrogen as?
urea and uric acid
How is ammonia transported safely in the bloodstream?
it is transported as glutamine
Where is excess glutamine processed?
intestines, kidneys and liver
What can pyruvate be converted to for transport to the liver?
alanine from glutamate donating ammonia to pyruvate
What is the Glucose-Alanine cycle?
the process by which the products of the degradation of muscle proteins are transported to the liver as alanine and reconverted to pyruvate that can then go on to be converted to urea to be excreted or be used in gluconeogenesis
Why must glutamate be converted to either glutamine or alanine to be transported back to the liver just to be converted back into glutamate again?
glutamate has a negative charge that makes it difficult to pass through membranes
Where (exactly) is excess glutamate metabolised?
in the mitochondria of hepatocytes
What is the reaction that occurs in the mitochondria of hepatocytes to degrade excess glutamate?
the glutamate dehydrogenase reaction
What happens in the glutamate dehydrogenase reaction?
two electron oxidation of glutamate followed by hydrolysis to form alpha-ketoglutarate and ammonium
How is ammonia recaptured from the glutamate dehydrogenase reaction?
via synthesis of carbamoyl phosphate which is the first nitrogen-acquiring reaction
What 2 ways does nitrogen enter the urea cycle?
- from carbamoyl phosphate
- by entry of aspartate
How many steps does the urea cycle have?
4
What are 2 fates of the carbon skeletons that result from the deamination of amino acids?
- converted to glucose
- oxidised as part of citric acid cycle
What are glycogenic amino acids?
those that can feed their carbon skeletons into gluconeogenesis
