3. NITROGEN FIXING: Bacteria take nitrogen gas (N 2 ) from air & transform or “fix” it into a form that ecosystem can use like ammonia (NH 3 ) N ≡N

4. AMMONIA: Created from nitrogen fixing bacteria, decay of plants & animals and from animal waste

5. AMMONIUM ION: (NH 4 + ) Produced by nitrogen fixing bacteria through ammonification

6. NITRIFICATION: Biological oxidation of ammonia with oxygen into nitrite (NO 2 - ) followed by oxidation of these nitrites into nitrates (NO 3 - ) O—N—O

7. NITRATE ION: inorganic (no C) formed by nitrification, easily taken up and used by plants

8. PROTEIN: Contains C, H, O & N; needed by body for growth, repair & to make enzymes

9. AMINO ACID: building block (or monomer) of protein. Has an amino group (-NH 2 ) & a carboxyl group (-COOH). 20 different kinds

10. DENITRIFICATION: Conversion of nitrates into nitrogen gas (N 2 ) by soil bacteria