7.19—Urea production and ultrafiltration

Amino-acid deamination produces ammonia, which is toxic. In the liver, the urea cycle converts ammonia into urea, a less toxic soluble compound transported in the blood to the kidneys.

Urea can be filtered and excreted in urine, allowing nitrogen from excess amino acids to leave the body without ammonia accumulating in tissues.

After a high-protein meal, more amino acids may be deaminated; increased urea production reflects nitrogen disposal, not direct protein storage.

Deamination is not the same as digestion, and urea is not formed in the nephron. Keep liver conversion, blood transport and kidney excretion separate.