Some amino acids are essential, that is, they cannot be synthesized. For all the others, however, you need building blocks. Nitrogen, and specifically ammonia, is required for non-essential amino acid synthesis, the transfer of which is accomplished through a process called transamination. Amino acids are also broken down for energy as a metabolic process,...
The answer to this question is quite simply this:
The activation energy for the uncatalysed reaction is such that the
amount of decomposition of urea in aqueous solution at blood temperature and
pH is negligible in the time taken for the transfer of urea to the
The literature supporting this is very old, so I shall first cite a relatively ...
[OP claim:] Urea in water can decompose into ammonia which is toxic.
Probably not as easily as you think. If Wikipedia is correct:
Urea alone is very stable due to the resonance forms it can adopt.
Some bacteria use urease to catalyze the reaction by 14 orders of magnitude (says Wikipedia).
There are some primary sources from the ...
The premise of the question is incorrect. Mammalian organisms do recycle nitrogen. They only excrete excess nitrogen.
Ammonia from deamination of amino acids can be incorporated into glutamate and glutamine:
Transamination can then transfer the amino group from glutamate, for example, to other ketoacids for the synthesis of other amino acids.
The capacity ...
Short answer: This is because the most common form of nitrogen found in multicellular organisms (not incorporated into any other compound) i.e. ammonia is too toxic to be stored or recycled.
Background: Ammonia, the product of deamination of amino acids, is basic in nature ($NH_3~+~H_2O \rightarrow NH_4OH \rightleftharpoons NH_4^+ + OH^-$) and thus disturbs ...
Preamble: The problem with questions on evolution
Obviously, evolutionary biology is a reputable discipline, but unfortunately there are two types of questions on evolution that are posted on this site that I believe are often of dubious value and can lead to dangerously unscientific habits of mind.
The first is questions of the type “Why did such and ...
Addressing the first part of your question:
Is it common for most soil bacteria to make significant quantities of
nitrous oxide after ammonia is added, or is there only a small subset
of bacteria present in soil that might do this?
No, not all soil bacteria can oxidize ammonia. According to wiki:
The oxidation of ammonia into nitrite is performed ...
if I give you a can of anhydrous ammonia, and I drop in a match, it will blow up, yielding nitrous oxides.
it is an exothermic energy releasing reaction.
bacteria figured this out, and use this same chemical reaction, albeit with more steps, to derive their own energy, and therefore drive their own matabolism.
like the way a marshmallow (sugar) will burn, ...