Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

One important metabolic pathway named for a compound containing this element generates ornithine and its namesake substance, urea. Pyrimidine and purine bases, such as adenine and thymine, are often given a name that reflects their containing this element. Bacteria fix this element by forming ammonia. For 10 points, name this element found in the amino group of amino acids, whose diatomic form is an inert gas.
Science