Nitrogen and Its Forms

What percentage of the atmosphere is composed of nitrogen gas (N₂)?

• 21%

• 78%

• 50%

• 10%

Which of the following is an organic form of nitrogen?

• Amino acids

• Proteins

• NH₄⁺ and NH₃

• Nucleic acids

Tags

NGSS.HS-LS1-6

Which organisms assimilate nitrogen from food in the form of amino acids and nucleic acids?

• Autotrophs

• Heterotrophs

• Fungi

• Prokaryotes

What process involves the conversion of ammonium to nitrate and nitrite?

• Nitrogen fixation

• Nitrification

• Nitrate and nitrite reduction

• Denitrification

Tags

NGSS.HS-LS2-3

Which process is responsible for the conversion of atmospheric nitrogen to a form usable by plants?

• Mineralization

• Nitrogen fixation

• Denitrification

• Nitrification

Why does this graph suggest that nitrogen-fixing bacteria should down-regulate genes for nitrogen fixation if nitrate or ammonium are available?

• Because nitrate and ammonium are more energy-efficient sources of nitrogen.

• Because nitrogen fixation is not necessary in the presence of oxygen.

• Because nitrate and ammonium are toxic to bacteria.

• Because nitrogen fixation requires less energy than using nitrate or ammonium.

Tags

NGSS.HS-LS2-3

What is the role of a heterocyst in cyanobacteria?

• Photosynthesis

• Nitrogen fixation

• Respiration

• Fermentation

Why is nitrogenase sensitive to O₂?

• It requires high oxygen levels to function

• Oxygen inhibits its activity

• It uses oxygen as a substrate

• Oxygen enhances its activity

Tags

NGSS.HS-LS2-3

What is the significance of nitrogen-fixing cyanobacteria in lakes?

• They increase oxygen levels

• They fix carbon dioxide

• They provide essential nitrogen

• They reduce water pollution

Which of the following is a source of atmospheric nitrogen deposition?

• Lightning

• Photosynthesis

• Ocean currents

• Soil erosion