nitrogen Flashcards
Where is nitrogen found in the body?
amino acids, ammonia and urea
name three stages of protein digestion
Gastric, Pancreatic and Intestinal
what happens during gastric digestion?
Proteins denatured by HCL which leaves them more open to the actions of pepsin
what occurs during pancreatic digestion?
pancreatic enzymes create a mix of free amino acids and short peptides 2-8 units in length.
what occurs during intestinal digestion?
free amino acids absorbed into portal system - di/tripeptides are absorbed and broken down to free amino acids in enterocytes in the brush border.
what is the only animo acid that can obtain nitrogen from ammonia?
Glutamate
how do other amino acids obtain nitrogen
from pre- existing amino acids through transaminase reactions > interconversion between a pair on amino acids and a pair of keto acids
how specific are transaminase enzymes?
they are specific to only one pair of amino acids and a pari of kept acids.
once broken down to individual amino acids, what can the remaining carbon skeletons be further catalysed into?
intermediates for the citric acid cycle and glycolysis
what intermediate does alanine form?
pyruvate
what intermediate does aspartate form?
oxaloacetate
can glycogenic amino acids be converted to glucose?
aye
what happens to ketogenic amino acids?
can be catabolised for energy in the citric acid cycle or be used to form ketone bodies.
what amino acids transfer nitrogen through the body?
glutamate and alanine.
nitrogen created from catabolised processes can be transported back to the liver as what?
alanine - it builds up as glucose here
nitrogen > alanine > liver >glucose
What else does this process require and what does it form?
requires transferase enzymes to convert alanine into pyruvate (or vice versa)
Also forms ammonia and urea in the liver
Why is nitrogen transported as glutamate and alanine?
glutamate has - charge, needs a cation
charge means it does not pass readily through the membrane
Alanine and glutamate together have no charge
how is urea formed from ammonia that comes from amino acids?
ammonia is formed by oxidative deamination.
Glutamate looses its nitrogen as ammonia
This is fed into the urea cycle
