question_answer 39)

  When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of this nitrogen? (a) It moves along with oxygen into the cells (b) it comes out with the  during exhalation (c) It is absorbed only by the nasal cells (d) Nitrogen concentration is already more in the cells so it is not at all absorbed.

Answer:

  (b) Elemental nitrogen in the atmosphere cannot be used directly by either plants or animals, and must be converted to a reduced state to be useful for higher plants and animals. Precipitation often contains little quantities of ammonium and nitrate resulting from nitrogen fixation by lightning. Certain specific bacteria possess nitrogen?s enzymes that can fix atmospheric nitrogen into a form (ammonium ion) that is chemically useful to higher organisms.