Flashcards in Nitrogen Deck (17):
State the main nitrogen containing molecules in the body
Mainly found in amino acids, ammonia and urea within the body
Protein digestion can be split into what three stages?
What happens in the gastric stage of protein digestion?
Denaturation of proteins by HCl leaves them more open to the actions of pepsin
What happens in the pancreatic stage of protein digestion?
Pancreatic enzymes create a mix of free amino acids and short peptides around 2-8 units in length
What happens in the intestinal stage of protein digestion?
- free amino acids are absorbed into portal system
- di/tri peptides are also absorbed and broken down to free amino acids in the enterocytes of the brush border
What is the only amino acid that can obtain its nitrogen from ammonia?
Where do all other amino acids obtain their nitrogen?
from pre-existing amino acids through transaminase reactions, involving the interconversion of a pair of amino acids and a pair of keto acids
Each transaminase enzyme is specific for
only one pair of amino acids and keto acids
Once broken down into individual amino acids, what can happen to the remaining carbon skeletons?
Remaining carbon skeletons can be further catabolised into intermediaries for the citric acid cycle and glycolysis e.g. alanine -> pyruvate, aspartate -> oxaloacetate
These intermediates can be converted into ___ via ___
What two fates are there for ketogenic amino acids?
- catabolised for energy in the CAC
- used to form ketone bodies
How is nitrogen transferred in the body?
Using glutamine and alanine
Nitrogen created from catabolised protein in muscles can be transported
back to the liver as alanine, where it is built up into glucose once more
The process of alanine -> glucose in the liver creates
ammonia and urea in the liver and also requires the use of the transferase enzymes to convert alanine into pyruvate or vice versa
Give three reasons why nitrogen is transported as glutamine and alanine instead of glutamate
- glutamate has a net negative charge so transporting it would require an accompanying cation
- this charge also means it does not pass readily through membranes
- alanine and glutamine bear no net charge
How is urea formed?
From the ammonia that comes from several of the reactions involving amino acids