Let's walk through the metabolic pathway of nitrogen in biodegradable material in the presence of oxygen, which is an aerobic environment.
1. Introduction:
In aerobic conditions, microorganisms decompose biodegradable material through a series of steps. The nitrogen within this material undergoes a transformation known as nitrification.
2. Nitrification Process:
- Step 1: Ammonification: Initially, organic nitrogen compounds (like proteins, amino acids) are converted into ammonia (NH₃) by microorganisms. This process is known as ammonification.
[tex]\[
\text{Organic Nitrogen} \rightarrow NH₃
\][/tex]
- Step 2: Conversion to Ammonium: In aqueous environments, ammonia can quickly pick up a hydrogen ion (proton) to form ammonium ions (NH₄⁺).
[tex]\[
NH₃ + H^{+} \rightarrow NH₄^{+}
\][/tex]
- Step 3: Nitrification: Once ammonium is formed, a two-step bacterial process called nitrification occurs:
- Step 3.1: Ammonia oxidation: Ammonium (NH₄⁺) is first oxidized to nitrite (NO₂⁻) by ammonia-oxidizing bacteria (like Nitrosomonas).
[tex]\[
NH₄^{+} + 1.5 O_2 \rightarrow NO_2^{-} + 2H^{+} + H_2O
\][/tex]
- Step 3.2: Nitrite oxidation: Nitrite (NO₂⁻) is then further oxidized to nitrate (NO₃⁻) by nitrite-oxidizing bacteria (like Nitrobacter).
[tex]\[
NO_2^{-} + 0.5 O_2 \rightarrow NO_3^{-}
\][/tex]
3. Final Product:
Through the detailed steps above, we can see that in the presence of oxygen (aerobic conditions), the end product of the nitrogen transformation from biodegradable material is nitrate (NO₃⁻).
4. Conclusion:
Thus, the nitrogen present in biodegradable material primarily ends up as the nitrate ion (NO₃⁻).
Based on the provided options:
1. [tex]$NH₃$[/tex] (Ammonia) - Incorrect
2. [tex]$NH₄^{+}$[/tex] (Ammonium ion) - Incorrect
3. [tex]$NO$[/tex] (Nitric oxide) - Incorrect
4. [tex]$NO₂$[/tex] (Nitrite ion) - Incorrect
5. [tex]$NO₃⁻$[/tex] (Nitrate ion) - Correct
The correct choice is:
c. 5
