nutrient cycles

Question 1

describe the nitrogen cycle (include
ammonification, nitrification, nitrogen fixation and denitrification)

Answer 1

Nitrogen-fixing bacteria can break the triple bond between the two
nitrogen atoms in nitrogen gas in the atmosphere and fix this
nitrogen into ammonium ions. The bacteria are either free-living in the
soil or symbiotic (mutualistic relationship), living in the root nodules
of plants. This is common in leguminous plants such as clover and
beans.
Nitrification
The ammonium ions in the soil are converted to nitrite and then
nitrate ions in the soil by nitrifying bacteria. This is a two-stage
oxidation reaction.
Denitrification
This stage is not useful as it returns the nitrogen in compounds back
to nitrogen gas in the atmosphere, so it cannot be absorbed by plants.
Anaerobic denitrifying bacteria do this.
Ammonification
Proteins, urea and DNA can be decomposed in dead matter and waste
by saprobionts. These are bacteria and fungi that can digest waste
extracellularly and return ammonium ions to the soil; this is
saprobiotic nutrition.

Question 2

describe the role of saprobionts in
decomposition.

Answer 2

These microbes will respire on dead or
waste organic matter. This will cause
decay and recycle nutrients into the soil
so plants can absorb the
nitrates/phosphates via active transport
in their root hair cells

Question 3

describe the role of mycorrhizae

Answer 3

Mycorrhizae are fungal associations
between plant roots and beneficial fungi.
The fungi entwined around the plant
roots provide a larger surface area for
water and mineral absorption. The fungi
part of the mycorrhizae acts like a
sponge and can absorb and hold onto
water and minerals surrounding the root

Question 4

describe the role of bacteria in the nitrogen
cycle

Answer 4

Bacteria are used in saprobiotic
nutrition, ammonification, nitrification,
nitrogen fixation and denitrification to
convert nitrogen-containing compounds
into other N-containing compounds

Question 5

why do organisms need
nitrogen?

Answer 5

To create amino
acids/proteins, DNA,
RNA and ATP.

Question 6

What is phosphorous needed for?

Answer 6

To create DNA, RNA, ATP and phospholipid bilayers.

Question 7

Describe how the phosphorous cycle differs from the nitrogen
cycle