Nitrogen Cycle Flashcards

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Overview: What is the Nitrogen Cycle?

A biogeochemical cycle where nitrogen moves between:
• Atmosphere (N₂)
• Living organisms
• Soil
• Water bodies

What is Nitrogen Fixation?

Conversion of N₂ → NH₃/NH₄⁺
• Biological: Rhizobium
• Physical: Lightning
• Industrial: Haber process

What is Ammonification?

Conversion of organic N → NH₃
• By decomposers
• From dead organisms
• From animal waste

Nitrification Step 1

NH₃/NH₄⁺ → NO₂⁻
• By Nitrosomonas bacteria
• Requires oxygen
• First step of nitrification

Nitrification Step 2

NO₂⁻ → NO₃⁻
• By Nitrobacter bacteria
• Requires oxygen
• Produces nitrate

What is Denitrification?

NO₃⁻ → N₂ gas
• By denitrifying bacteria
• Anaerobic conditions
• Returns N₂ to atmosphere

Plant Nitrogen Use

• Absorb NO₃⁻ through roots
• Convert to amino acids
• Make proteins
• Essential for growth

Root Nodules

Structures in legume roots:
• Contain Rhizobium
• Site of N₂ fixation
• Mutualistic relationship

Human Impact

• Artificial fertilizers
• Industrial fixation
• Eutrophication
• Nitrate pollution

Environmental Issues

• Nitrate leaching
• Water pollution
• Algal blooms
• Ecosystem disruption

Agricultural Importance

• Crop nutrition
• Fertilizer use
• Legume rotation
• Soil fertility

Required Conditions

• Temperature
• pH levels
• Oxygen availability
• Moisture levels