13.2 - Nitrogen Cycle

Question 1

What is the importance of the nitrogen cycle?

Answer 1

Recycles nitrogen - an essential element for life on Earth.

no nitrogen = decline in vital biological molecules needed by organisms

Question 2

What molecules need nitrogen?

Answer 2

• Proteins
• DNA
• RNA

Question 3

What percentage of the atmosphere is nitrogen gas?

Answer 3

78%

Question 4

What are the four key processes of the nitrogen cycle?

Answer 4

Nitrogen fixation

Question 5

What is nitrogen fixation?

Answer 5

Conversion of nitrogen gas into nitrogen-containing compounds

Question 6

What organisms fix nitrogen?

Answer 6

Mutualistic bacteria

Question 7

What abiotic processes fix nitrogen?

Answer 7

Lightning

Question 8

What is ammonification?

Answer 8

Conversion of organic nitrogen into ammonia or ammonium ions

Question 9

How does ammonification make substances available to plants?

Answer 9

Saprobionts decompose organic matter into NH4+

Question 10

What is nitrification?

Answer 10

Oxidation of ammonia and ammonium ions to nitrites and nitrates

Question 11

What are the two stages of nitrification?

Answer 11

Bacteria oxidize NH3/NH4+ to NO2-

Question 12

What is denitrification?

Answer 12

Conversion of nitrates back into nitrogen gas

Question 13

What organisms carry out denitrification?

Answer 13

Denitrifying bacteria

Question 14

What conditions favor denitrification?

Answer 14

Anaerobic conditions