Nitrogen Cycle

Question 1

what is the process of mineralization?

Answer 1

When plants and animals die, microorganisms degrade their tissues. These microorganisms convert the complex organic material first into inorganic forms and then into forms that can be then taken up by organisms and converted into living tissue again

Question 2

what is the significance of plants and what critical role do they play in?

Answer 2

they play a critical role in energy cycling as primary producers

Question 3

what is a primary producer?

Answer 3

life forms that are able to capture energy from the sun and utilize it to fix atmospheric CO2 into organic carbon.

Question 4

What are the limiting organic materials in plants?

Answer 4

1. Nitrogen

2. phosphorus

Question 5

Inorganic forms of nitrogen?

Answer 5

1. N2 gas
2. Ammonia
3. Nitrate
4. nitrite

Question 6

Organic forms of nitrogen?

Answer 6

1. amino caids
2. nucleic acids
3. urea

Question 7

Problem with dinitrogen?

Answer 7

organisms cannot use N2 unless it has been reduced to ammonia (NH3) through nitrogen fixation (reduction)

Question 8

Examples of natural processes in nitrogen fixation?

Answer 8

Lightning, volcanic eruptions, uv light

Question 9

2 best way to do nitrogen fixation?

Answer 9

1. Soil microbes such as Rhizobium

2. Aquatic forms such as the cyanobacterium Anabaena

Question 10

Significance of ammonia formed by nitrogen fixation(reduction of nitrogen)?

Answer 10

It serves as a direct/indirect nitrogen source for plants and animals and once absorbed, it can be converted to cellular components such as amino acids, purines, and pyrimidines

Question 11

2 pathways for the use of ammonia by plants?

Answer 11

1. Assimilation of ammonia

2. oxidation of ammonia to nitrate (nitrification) and its subsequent use

Question 12

What are the two main sources of ammonia in the environment?

Answer 12

1. nitrogen fixation

2. ammonification

Question 13

Explain process of ammonification?

Answer 13

this process is the result of decomposition of dead animals and plants

Question 14

explain the process of microbial action and their contribution to the release of ammonia?

Answer 14

1. microbial action causes the hydrolysis of proteins and nucleic acids, releasing the amino acids and nucleotides
2. the nucleotides and amino acids are then further metabolized by microorganisms and the nitrogen released as ammonia

Question 15

what happens to ammonia produced by microbial action in the soil?

Answer 15

it is mostly absorbed by other microorganisms (very little by plant roots), and then taken into cell material. this is known as ammonia assimilation.

Question 16

what happens to the assimilated(taken up) nitrogen ?

Answer 16

it gets incorporated into cellular proteins and nucleic acid and travels through the food chain with little loss.

Question 17

What happens to the nitrogen that is uptaked into an organism?

Answer 17

1. it can either be lost through extretion as urea or ammonia
2. or it simply reincorporates itself into other nitrogenous compounds in the cell for as long as an organism is alive or when another organism eats it.

Question 18

When can the nitrogen content of plants or animals can be released as N2?

Answer 18

upon natural death and decomposition

Question 19

Explain the oxidation of ammonia to nitrate (nitrification)

Answer 19

in well aerated soils, two groups of strictly aerobic bacteria have the capacity to oxidize ammonia to nitrite and then further to nitrate. The two processes involve different bacteria and this entire oxidative process (nitrification) allows the bacteria to use the high-energy electrons thus released in the production of energy.

Question 20

What is the source of the high-energy electrons that the bacteria uses to reduce ammonia to nitrite and nitrate

Answer 20

. it comes from an inorganic compound.

Question 21

What is chemolithotrophic?

Answer 21

bacteria that uses high-energy electrons from an inorganic compound as a source

Question 22

What is nitrate assimilation ?

Answer 22

the process of nitrate uptake and utilization

Question 23

Conditions for the microbes involved in nitrification. (where does it work well?)

Answer 23

1. well aerated, warm, most soils

Question 24

Significance of Nitrate?

Answer 24

its the most useful form of nitrogen for plants

Question 25

Pros about nitrate assimilation by plants?

Answer 25

its the most profitable use of nitrates in soil or water.

Question 26

Two ways a plant can uptake nitrogen?

which is more efficient?

Answer 26

1. absorbs ammonia through its roots

2. absorbs nitrogen in form of nitrate

Question 27

Two possible pathways for nitrate use by microbes?

Answer 27

1. assimilatory nitrate reduction

2. Dissimilatory nitrate reduction or denitrification:

Question 28

Explain assimilatory nitrate reduction

Answer 28

there are microorganisms that can convert nitrate to nitrite and then ammonia (reverse reaction). The ammonia may not be very useful to plants but it can be absorbed by microbes and be taken up into cell material.

Question 29

Goal of assimilatory nitrate reduction?

Answer 29

it has the virtue of keeping the nitrogen in a state in which it can still be absorbed and used by living organisms

Question 30

Explain dissimilatory nitrate reduction or denitrification:

Answer 30

Organisms can use any existing nitrate or nitrite as terminal electron acceptors in order to continue to produce energy if soils are so poorly aerated. this form of anaerobic respiration (oxygen not being a terminal electron acceptor) results in nitrate being reduced to nitrite and further reduced to nitrogen gas. this form of nitrate reduction DOES NOT RESULT IN the incorporation of nitrogen into the cells.

Question 31

what is nitrate reduction?

Answer 31

reduction of nitrate to nitrite

Question 32

what is denitrification?

Answer 32

reducing nitrite to nitrogen gas