The Nitrogen Cycle

Question 1

state two things that plants need nitrogen for

Answer 1

To build amino acids, which are then synthesized into proteins during protein synthesis.

to build organic bases(nitrogenous bases) which are used in building nucleotides and nucleic acids

Question 2

In what forms do plants absorb nitrogen
Do plants absorb nitrogen gas?

Answer 2

As nitrates and ammonium ions through their roots
No, they don’t

Question 3

what percentage of the carbon dioxide taken in during photosynthesis is converted into proteins by plants

Answer 3

approximately 30%

Question 4

state the processes involved in the nitrogen cycle

Answer 4

nitrogen fixation
nitrification
de-nitrification
ammonification

Question 5

the four bacteria that are essential in the nitrogen cycle (and their functions)

Answer 5

putrefying bacteria and fungi( they decompose the in dead animals and plants )

nitrifying bacteria, i.e Nitrosomonas and Nitrobacter.( they convert ammonium ions nitrites and then nitrates)

de-nitrifying bacteria (they convert nitrates back into nitrogen gas )

nitrogen-fixing bacteria (to supply plants with the vital nitrogen that they cannot obtain from the air themselves)

Question 6

what happens after dead plants and animals are decomposed

Answer 6

their proteins are digested into amino acids, which are then deaminated to form NH2. The NH2 is reduced to produce ammonium ions.

Question 7

what is required for nitrifying bacteria to function and why
where are these bacteria found then

Answer 7

oxygen.
because they are aerobic.
they are found in aerated soils

Question 8

the two types of nitrogen-fixing bacteria

Answer 8

azotobacter
rhizobium

Question 9

azotobacter and it’s function

Answer 9

nitrogen-fixing bacteria that live freely in the soil. they can absorb nitrogen gas from the air and reduce it to ammonium

Question 10

rhizobium

Answer 10

nitrogen-fixing bacteria found in root nodules. the bacteria and the plant have a symbiotic relationship where the bacteria benefit by having food (sucrose) and shelter and the plants benefit by having amino acids produced by the bacteria.

Question 11

the enzyme contained by nitrogen-fixing bacteria and the function

Answer 11

nitrogenase
it catalyzes the reduction of nitrogen gas into ammonium ions

Question 12

by which process does the nitrogen get transported into the root nodules

Answer 12

diffusion

Question 13

de-nitrifying bacteria found in the soil

Answer 13

pseudomonas

Question 14

in what conditions do de-nitrifying bacteria thrive and where do they live as a result

Answer 14

anaerobic conditions
in water logged soils

Question 15

why do de-nitrifying bacteria live in waterlogged soils

Answer 15

because in these soils, there are few air spaces available, as there is a lot of water filling the air spaces. therefore, there are very few oxygens present in the soil, if any…..thereby providing the anaerobic conditions required by the bacteria

Question 16

by which process does man produce inorganic fertilizers

Answer 16

the Haber process

Question 17

how are organic fertilizers(slurry) produced

Answer 17

through intensive animal production

Question 18

Eutrophication

Answer 18

Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus

Question 19

algal bloom

Answer 19

where high levels of nutrients particularly nitrogen cause rapid growth of algae

Question 20

effects of eutrophication

Answer 20

the rapid growth of algae blocks light from reaching photosynthesizing plants in the waters. these plants die as a result
of saprophytic bacteria decomposing the dead plants and respiring aerobically, using up dissolved oxygen in the waters. this leads to high biological oxygen demand.
this decreases biodiversity in the habitat (waters).

nitrite and nitrate can also have a direct toxic effect on humans if found in the water supply

Question 21

4 measures to put in place to reduce eutrophication

Answer 21

restrict the amount of fertilizers applied to the soil
only apply the fertilizer when the plants are actively growing
crop rotation
try to avoid leaving the land bare as this encourages the leaching of nutrients from the soil

Question 22

TWO WAYS IN WHICH WE CAN INCREASE THE AMOUNT OF OXYGEN IN THE SOIL

Answer 22

through ploughing
by installing drainage systems to reduce waterlogging, thereby enabling natural aeration of the soil

Question 23

ploughing

Answer 23

the process of turning the soil over to increase the oxygen content of the soil

Question 24

in which conditions do nitrifying bacteria thrive

Answer 24

aerobic conditions

Question 25

four reasons for the loss of lowland raised bog habitat

Answer 25

peat extraction
afforestation
landfill development
drainage of surrounding areas