Which component of proteins is broken down to form urea?

Urea is a waste product formed from the breakdown of amino acids in the liver during a process known as deamination. When proteins are consumed, they are eventually broken down into their constituent amino acids. These amino acids undergo deamination, where the amino group (NH2) is removed. The resulting ammonia is then converted into urea, which is less toxic and can be safely excreted by the kidneys.

The other options are not involved in urea formation. Fatty acids are primarily used for energy and do not contribute to urea synthesis. Nucleotides are components of nucleic acids (DNA and RNA) and are involved in genetic processes, while monosaccharides are simple sugars that serve as energy sources, but they do not participate in protein metabolism in the same way that amino acids do. Thus, the breakdown of amino acids is directly responsible for the production of urea.