Answer the following question given this paragraph: 

Regulation of Nitrogen Wastes Nitrogen wastes are produced by the breakdown of proteins during normal metabolism. Proteins are broken down into amino acids, which in turn are deaminated by having their nitrogen groups removed. Deamination converts the amino (NH2) groups into ammonia (NH3), ammonium ion (NH4+), urea, or uric acid (Figure 25.22). Ammonia is extremely toxic, so most of it is very rapidly converted into urea in the liver. Human urinary wastes typically contain primarily urea with small amounts of ammonium and very little uric acid.


Q: Nitrogen wastes are produced by the breakdown of what during normal metabolism?

 Choices:

- enzymes

- hormones

- lipids

- proteins

A:
proteins
