Nitrogen 2 Flashcards
Removal of nitrogen from body
- amino acid metabolism or nitrogen metabolism results in formation of the product ammonia
- ammonia if present in too high a concentration is toxic.
- So the body has to have a way of detoxifying ammonia.
- The urea cycle is responsible for taking ammonia & turning it into urea, a product that’s not really very toxic + can be easily excreted in urine.
- Amino acids come from ingested proteins or breakdown of alanine (which is formed from muscle contraction) or glutamine (which is fromed from muscle breakdown).
- Amino acids from these various sources result in formation of ammonia
How is ammonia transported in the bloodstream?
As glutamine
Where is excess glutamine processed?
Intestines kidney and liver
Glutamate + ammonia =
Glutamine
How is alanine made?
Glutamate donates ammonia to pyruvate
Why is pyruvate converted to alanine?
Pyruvate builds up in an anaerobically working muscle - lactic acid build up. By forming alanine it can be transported to the liver
What happens to the protein that’s broken down during exercise?
Transported to the liver as alanine or glutamine. Carbon skeleton is converted into glucose or oxidised as part of the citric acid cycle. Nitrogen is excreted as ammonia and converted to urea by the urea cycle
Why is nitrogen transported through the body as glutamine and alanine instead of glutamate?
Glutamate has a negative charge - does not pass readily through cell membranesAlanine and glutamine do not bear charge
Where is excess glutamate metabolised?
Mitochondria of hepatocytes
What is the name of the process where glutamate loses its notrogen as ammoia to form alpha ketoglutarate? And what is the electron acceptor?
Oxidative deamination (two electron oxidation followed by hydrolysis) NAD+ and NADP+
What is the function of Carbomyl Phosphate?
Recaptures the ammonia from glutamate and enters the urea cycle.
How many essential amino acids exist (ones we can only obtain through our diet)?
8
What is the fate of ketogenic amino acids?
They are broken down to produce acetyl - CoA (forms ketone bodies or is oxidised in the citric acid cylce) and acetoacetylacetate.
What are glucogenic amino acids?
Feed in to gluconeogenesis and can produce glucose or glycogen in the liver.
Why can’t ketogenic amino acids produce glucose?
Pyruvate dehydrogenase reaction is irreversible (Pyruvate to acetyl CoA). No net increase in Oxaloacetate.
