Nitrogen Cycle

Flashcards to help study the nitrogen cycle

The nitrogen cycle is

The biogeochemical cycle whereby nitrogen is converted into various chemical forms.

Chemoautrophic bacteria can

Convert nitrogen gas into compounds that can be assimilated by plants and animals.

Nitrogen-fixing bacteria

Convert atmospheric nitrogen to ammonia.

Rhizobium

Associates with roots in a mutualistic relationship.

Nitrogen Fixation is

The conversion of inert nitrogen gas (N2) into ammonia (NH3).

Nitrogenase is

The enzyme that catalyses the conversion of inert nitrogen gas (N2) into ammonia (NH3).

Rhizobium

Forms nodules within the plant roots and supplies ammonia to the plant in exchange for carbohydrates.

Saprotrophs

Will decompose organic materials to produce ammonia (and ammonium ions).

Ammonification

Releases ammonium ions into the soil which can be absorbed by plants.

Nitrification is

The conversion of ammonium ions into nitrites (NO2 –) and nitrates (NO3 – ) by nitrifying bacteria in the soil.

Nitrosomonas

Converts ammonium ions into nitrites.

Nitrobacter

Can convert the nitrites into nitrates.

Denitrifying bacteria

Reduce nitrate in the soil in the absence of oxygen.

Denitrification is

A chemical reduction process that converts nitrates (NO3 –) into nitrogen gas (N2).

Denitrifying bacteria

Uses nitrates instead of oxygen as an electron acceptor during cellular respiration, producing nitrogen gas.