* Proteins: Nitrogen is a key component of amino acids, the building blocks of proteins. It is found in the amino group (-NH2) of each amino acid.

* Nucleic acids (DNA and RNA): Nitrogen is found in the nitrogenous bases that make up DNA and RNA (adenine, guanine, cytosine, thymine, and uracil).

* Some carbohydrates: While most carbohydrates don't contain nitrogen, a few exceptions exist, such as chitin (found in the exoskeletons of insects and crustaceans) and some bacterial polysaccharides.

Note: Lipids (fats and oils) generally do not contain nitrogen.