Nitrogen Cycle

Question 1

What is the importance of nitrogen? (N2)

Answer 1

• Vital constituent of protein molecules.
• If nitrogen was not available to plants- could not be synthesised and complex life forms could never have existed.
• Forms most of Earth’s atmosphere

Question 2

What two ways can nitrogen enter the soil?

Answer 2

Lightning

• Nitrogen from the air combines with other elements in the air and form simple compounds- nitrogen oxides
• Carried to the earth will rain and enter the soil

Certain bacteria in the soil

• use nitrogen gas and covert it to nitogen compounds
• Some bacteria are living freely in the soils
• Others live within the roots of leguminous plants- (peas, clover, beans). Not used within bacteria cells but released into soil

Question 3

How are nitrogen compounds used in the soil?

Answer 3

• Absorbed in the soil

- Synthesise organic nitrogen compounds- amino acids

Question 4

How do the nitrogen compounds move?

Answer 4

• Herbivores and carnivores carry the organic nitrogen compounds through their particular food chains
• Then nitrogen is incorporated into animal protein molecules
• Nitrogen occurs in waste products of animal metabolism (= products of excretion- like urea)
• Living organisms return the some nitrogen back into the environment

Question 5

How are protein molecules broken down?

Answer 5

• Animals (highest trophic level) die- decomposers break down organic compounds of their bodies
• This releases further nitrogen compounds into the environment.

Question 6

The process of protein compounds changing

Answer 6

• Ammonification bacteria covert protein molecules to ammonia (NH3)
• Nitrification bacteria convert ammonia to nitrite compounds (contain NO-2)
• Nitrification bacteria convert them to nitrate compounds (contain NO-3)- nitrates are an inorganic from which is reused by plants

Question 7

What bacteria completes the nitrogen cycle?

Answer 7

• Dentrifying bacteria in the soil- breaks down nitrogen compounds and release nitrogen gas back into the atmosphere

Question 8

Why the nitrogen cycle almost perfect?

Answer 8

• There is little net gain or loss of the nitrogen.