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Biochem, Nutrition Question about Protein


#1

You may know about protein poisoning, or Rabbit starvation; a situation where individuals eating nearly 100% protein die of malnutrition because the body can only turn a limited amount into glucose or fat.

I have read that at above about .7 grams of protein per pound of bodyweight excess protein ends up as Urea, and that at above about .85 it tends to end up as Ammonia.

Can someone clarify what is going on when protein gets turned into urea or ammonia? When protein gets turned into urea, are the calories lost, or is urea just where the nitrogen ends up after the excess protein gets turned into glucose? Also same for Ammonia? It seems like having protein lost as urea means that you are losing those calories since there is carbon lost in the end product, while ammonia has no carbon so I would think that the carboxylic acid portion of the amino acid is getting turned into glucose?

(that is a question)

Anyway, why would urea be produced first and then ammonia, or is there always a mix of the two? How are calories just lost in the case of Rabbit starvation? What is the fate of the carboxylic backbone.

Also wondering if insulin would tend to be high or low during periods of ammonia buildup?

So basically, how do you get from amino acids to ammonia and urea and when do amino acids yield glucose and when don’t they? Why can you only turn a limited amount of amino acids into glucose? Is it limited by the liver?