Question

Which of the following is NOT true of bacteria?

a) Bacteria change nitrogen into a form plants can use.
b) Bacteria change oxygen into nitrogen.
c) Bacteria change the sugar in milk to lactic acid.
d) Bacteria change harmful chemicals into harmless ones.

Answer 1

The false statement about the nitrogen cycle is (c), 'Nitrification by bacteria converts nitrates (NO3-) to nitrites (NO2-),' because in reality, nitrification involves bacteria converting ammonium to nitrites, and then nitrites to nitrates, not the reverse.

Step-by-step explanation:

To address the student's question about which statement regarding bacteria and the nitrogen cycle is not true, we need to examine the processes involved in the nitrogen cycle. We have the following statements to evaluate:

• Ammonification converts organic nitrogenous matter from living organisms into ammonium (NH4+).
• Denitrification by bacteria converts nitrates (NO₃⁻) to nitrogen gas (N₂).
• Nitrification by bacteria converts nitrates (NO₃⁻) to nitrites (NO₂⁻).
• Nitrogen-fixing bacteria convert nitrogen gas (N2) into organic compounds.

The process of nitrification actually involves two steps:

1. Conversion of ammonium (NH₄⁺) to nitrites (NO₂⁻), which is known as nitrosification.
2. Conversion of nitrites to nitrates (NO₃⁻), not the other way around as stated in the false statement (c.).

Therefore, the correct answer to the question, 'Which of the following statements about the nitrogen cycle is false?' is (c) 'Nitrification by bacteria converts nitrates (NO₃⁻) to nitrites (NO₂⁻).'