Ammonification in the nitrogen cycle Steps:

• Decomposers like bacteria and fungi break down dead plant and animal matter containing proteins.
• Proteins are hydrolyzed into amino acids, which undergo deamination.
• Deamination releases ammonia (NH3), which reacts with water in soil to form ammonium ions (NH4+).
• This process, called ammonification, recycles nitrogen for plants.

Why A is correct:

• Ammonification directly converts organic nitrogen in proteins to ammonium ions, the initial product of decomposition.

Why the others are wrong:

• B: Nitrogen gas results from denitrification, where anaerobic bacteria reduce nitrates, not from protein breakdown.
• C: Nitrate ions form later in nitrification, when aerobic bacteria oxidize ammonium.
• D: Nitrite ions are a temporary intermediate in nitrification, not a direct product of decomposition.

Final answer: A