Nitrogen Cycle

Question 1

What process converts N2 into NH4+?

Answer 1

nitrogen fixation

Question 2

What are 2 examples of anaerobic conditions?

Answer 2

• very compact soil
• water-logged soil

Question 3

Draw the nitrogen cycle

Answer 3

use book

Question 4

How are plants involved in the nitrogen cycle?

Answer 4

they assimilate NO3 (using it in proteins, DNA, RNA etc.)
their nitrogen containing compounds are broken down by saprobionts

Question 5

How can lightning be involved in the nitrogen cycle?

Answer 5

it can break the bond between N2, allowing nitrogen to react with oxygen and form nitrates, without the need for bacteria

Question 6

How are nitrate ions taken up by roots?

Answer 6

active transport

Question 7

What are the 4 main stages in the nitrogen cycle?

Answer 7

• nitrogen fixation
• nitrification
• ammonification
• denitrification

Question 8

What is ammonification?

Answer 8

production of ammonia from nitrogen containing compounds (eg urea, proteins and nucleic acids) found in waste and dead organisms

Question 9

What do ammonifying bacteria do?

Answer 9

convert ammonia containing molecules into ammonium ions

Question 10

What microorganisms carry out ammonification?

Answer 10

saprobionts

Question 11

What is nitrification?

Answer 11

the oxidation reaction converting ammonium ions into nitrate ions

Question 12

What microorganisms carry out nitrification?

Answer 12

nitrifying bacteria

Question 13

What is required for nitrifying bacteria to carry out nitrification?

Answer 13

oxygen (aerated soil)

Question 14

What is nitrogen fixation?

Answer 14

the process converting atmospheric nitrogen into ammonia and ammonium ions

Question 15

What are the types of nitrogen fixing bacteria?

Answer 15

free-living and mutualistic

Question 16

What are free-living nitrogen fixing bacteria?

Answer 16

• live in soil
• convert nitrogen to ammonia and use this to form amino acids and nitrogen containing compounds which are released when they die

Question 17

What are mutualistic nitrogen fixing bacteria?

Answer 17

• live on nodules of roots (of leguminous plants)
• form ammonia from nitrogen and use this to make a/a

Question 18

Why are mutualistic nitrogen-fixing beneficial to the plant? What do they benefit from?

Answer 18

• plants obtain amino acids
• bacteria obtain carbohydrates

Question 19

What is denitrification?

Answer 19

nitrates in soil are converted to atmospheric nitrogen

Question 20

What microorganism carries out denitrification?

Answer 20

anaerobic denitrifying bacteria