NITROGEN CYCLE - AP BIO

Nitrogen Cycle

Cyclic movement of nitrogen of nitrogen in different chemical forms from the environment to organisms and then back to the environment.

Nitrogen Fixation

Conversion of atmospheric nitrogen gas into forms useful to plants by lightening, bacteria, and cyanobacteria; it is part of the nitrogen cycle.

N2 --> NH3

Nitrogen gets "fixed" when it is combined with oxygen or hydrogen.

Nitrification

Ammonia is converted to nitrite, then to a nitrate.

-Nitrifying bacteria in soil combine ammonia with oxygen

-Ammonia changes to nitrites

-Nitrifying bacteria in soil convert nitrites to nitrates

-Plants absorb nitrates and grow!

Assimilation

Plant roots absorb ammonium ions and nitrate ions for use in making molecules such as DNA, amino acids, and proteins.

Ammonification

Bacteria decomposers break down amino acids from dead animals and wastes into nitrogen ammonium (NH4).

NH3 --> NH4

Major Sink

Atmosphere (makes up 78% of the air)

What happens to atmospheric nitrogen(N2) in the nitrogen cycle?

Atmospheric nitrogen is converted to ammonia or nitrates.

Ammonia (NH3)

Nitrogen combines with Hydrogen to make Ammonia

Nitrates (NO3)

Nitrogen combines with Oxygen to make Nitrates

Why does atmospheric nitrogen need to be converted?

Although the majority of the air we breathe is nitrogen, most living organisms are unable to use nitrogen as it exists in the atmosphere.

How does atmospheric nitrogen get changed into a form that can be used by most living organisms?

By traveling through one of the major processes in the Nitrogen Cycle:

Nitrogen Fixation

Ammonification

Nitrification

Denitrification

Assimilation

three ways that nitrogen gets "fixed"

1. Atmospheric fixation (lightning)

2. Industrial fixation (fertilizer)

3. Biological Fixation

Atmospheric Fixation

• Nitrogen combines with Oxygen

• Nitrogen oxides forms

• Nitrogen oxides dissolve in rain and change to nitrates

• Plants use nitrates to grow!

Industrial Fixation

• Industrial Plant combines nitrogen and hydrogen

• Ammonia is formed

• Ammonia is used a fertilizer in soil

Biological Fixation

where MOST nitrogen is fixed

2 types of nitrogen fixing bacteria:

• Free Living Bacteria

cyanobacteria

-Symbiotic Relationship Bacteria

(Rhizobium) in

Leguminous plants

Ammonia

Most atmospheric nitrogen (N2) is "fixed" and changed to ammonia (NH3). Ammonia is highly toxic to many organisms.

How Ammonification Happens

-Bacteria converts organic nitrogen to ammonium (NH4)

-Ammonium (NH4) is used by some plants

-Ammonium (NH4) is stored in soil.

What happens to ammonium (NH4) storedin the soil?

It travels through thenext processof the nitrogen cycle called Nitrification.

How many steps is nitrification

2 steps

Step one of nitrification

Ammonium Oxidation. The microorganisms involved are called the ammonia oxidizers.

-Nitrosomonas

-Nitrosospira

-Nitrosococcus

-Nitrosolobus

Step two of nitrification

Nitrite Oxidation

Microorganism involved: Nitrobacter

How does nitrogen reenter the atmosphere in the nitrogen cycle?

Through the next process called denitrification

denitrification

(Anaerobic) Nitrate ions and nitrite ions are converted into nitrous oxide and nitrogen gas (N2)

NO3 --> N2

Human Influences on Cycle

Fertilizers from agriculture

Animal Waste

Fertilizers

Wastewater Treatment (Blue Plains)

Denitrifying Bacteria

The denitrifying bacteria use nitrates as an alternative to oxygen, leaving free nitrogen gas as a byproduct.

Importance to living things

is an essential component of DNA, RNA, and proteins—the building blocks of life.

Processes/molecular transformations

Nitrogen Fixation-N2 to Nitrate or Ammonia

Assimilation- compounds to plant/animal body

Nitrification NH4 to NO2 to NO3

Ammonification biological N to NH4

Denitrification NO3 to N2