The urea cycle describes how liver cells convert ammonia to urea. Ammonia is a toxic waste product of protein catabolism. Land animals must convert ammonia into the less toxic urea which can be safely eliminated by the kidneys through urine. Marine animals excrete ammonia directly, and the surrounding water dilutes the ammonia to safe levels.

Renal function tests are crucial for assessing kidney health, monitoring disease progression, and evaluating the kidneys' efficiency in waste elimination, fluid balance, and electrolyte regulation. These tests offer critical insights into kidney function, even though routine measurements may appear normal until there is a significant decline in the glomerular filtration rate or GFR. Typically, signs of kidney impairment only become evident when the GFR falls to about 50% of its normal level.

Animals have evolved different strategies for excretion, the removal of waste from the body. Most waste must be dissolved in water to be excreted, so an animal’s excretory strategy directly affects its water balance.

Direct alkylation is not a suitable method for synthesizing amines because it produces polyalkylated products. Gabriel synthesis is the most preferred method to exclusively make primary amines. The method uses phthalimide, which contains a protected form of nitrogen that participates in alkylation only once to predominantly give primary amines.
Strong bases like NaOH or KOH deprotonate the phthalimide to form the corresponding anion, which acts as a nucleophile. Further, the anion attacks an...