Nitrite in the nitrogen cycle is best described as:

Nitrite in the nitrogen cycle is best described as:

• A. A primary energy source for bacteria
• B. A final stable form of nitrogen in water
• C. An intermediate produced from ammonia oxidation
• D. A salinity-related compound

Answer: (C)

Nitrite serves as an intermediate in the nitrification process. In oxygenated environments, ammonia-oxidizing organisms convert ammonium (NH4+) to nitrite (NO2−), and then nitrite-oxidizing organisms take that nitrite and oxidize it to nitrate (NO3−). This two-step sequence is how ammonia becomes nitrate, with nitrite bridging the two steps. The energy that drives nitrification comes from the oxidation of ammonia, not from nitrite itself, so nitrite isn’t the primary energy source. It’s also not the final stable form in water—nitrate is typically the end product—nor is nitrite related to salinity. Hence, describing nitrite as the intermediate produced from ammonia oxidation best captures its role in the cycle.

Nitrite serves as an intermediate in the nitrification process. In oxygenated environments, ammonia-oxidizing organisms convert ammonium (NH4+) to nitrite (NO2−), and then nitrite-oxidizing organisms take that nitrite and oxidize it to nitrate (NO3−). This two-step sequence is how ammonia becomes nitrate, with nitrite bridging the two steps. The energy that drives nitrification comes from the oxidation of ammonia, not from nitrite itself, so nitrite isn’t the primary energy source. It’s also not the final stable form in water—nitrate is typically the end product—nor is nitrite related to salinity. Hence, describing nitrite as the intermediate produced from ammonia oxidation best captures its role in the cycle.