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Q49 — Biological Nitrogen Fixation — Diazotrophs and Nitrogenase

Theoretical 1 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Mineral Nutrition & Nutrient Uptake

Only some bacteria and archaea are capable of performing biological nitrogen fixation. Organisms that grow on N₂ as their sole nitrogen source are called diazotrophs and play an essential role in the biosphere.

Determine whether the following statements are true or false:

A. Diazotrophs fix nitrogen in the form of nitric acid.
B. The process of nitrogen fixation consumes a lot of energy.
C. The enzyme nitrogenase which catalyzes nitrogen fixation requires an organic source of nitrogen as a substrate for catalytic activity.
D. Nitrogen fixation requires molecular oxygen.
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Question reproduced from IBO 2022, Theoretical Paper 1, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)