Cycles

Question 1

Saprobionts

Answer 1

Feed on remains of dead
organisms and their waste
products (faeces/urea) and
break down organic molecules
secrete enzymes for
extracellular digestion
involved in decomposition

Question 2

Mycorrhizae

Answer 2

Symbiotic relationship between
fungi and roots of plants
fungi act as extensions of roots
increase surface area of system -
increasing rate of absorption of
water and mineral ions
mutualistic relationship as plants
supply fungi with carbohydrates
from photosynthesis

Question 3

Importance of
nitrogen to
organisms

Answer 3

Used to create
amino acids / proteins
DNA
RNA
ATP

Question 4

Nitrogen cycle
stages

Answer 4

Nitrogen fixation
nitrification
denitrification
ammonification

Question 5

Nitrogen
fixation

Answer 5

Nitrogen fixing bacteria break
triple bond between two
nitrogen atoms in nitrogen gas
fix this nitrogen into
ammonium ions

Question 6

Nitrogen fixing
bacteria

Answer 6

Fix nitrogen gas into ammonium
ions
free living in soil
or form mutualistic relationship
on root nodules of leguminous
plants
give plants N in exchange for
carbohydrates

Question 7

Nitrification

Answer 7

Ammonium ions in soil are
oxidised to nitrite ions
nitrite ions are oxidised to nitrate
ions
by nitrifying bacteria

Question 8

Denitrification

Answer 8

Returns nitrogen in compounds
back into nitrogen gas in
atmosphere
by anaerobic denitrifying
bacteria

Question 9

Ammonification

Answer 9

Proteins / urea / DNA in dead
matter and waste are
decomposed by saprobionts
return ammonium ions to the
soil

Question 10

Importance of
phosphorius

Answer 10

Used to create:
DNA
RNA
ATP
phospholipid bilayers
RuBP / GP/ Triose phosphate

Question 11

Role of
saprobionts in
nitrogen cycle

Answer 11

They use enzymes to
decompose
proteins/DNA/RNA/urea in
waste and dead organisms
releasing ammonium ions