CICLO DO NITROGÊNIO - CICLOS BIOGEOQUÍMICOS | Biologia com Samuel Cunha

Summary

This educational video explains the nitrogen cycle, focusing on the processes of nitrogen fixation, nitrification, and denitrification. The presenter highlights the role of nitrogen-fixing bacteria, such as *Rhizobium* and cyanobacteria, in converting atmospheric nitrogen into usable forms for plants. The video also covers the importance of nitrification, where ammonia is converted into nitrites and nitrates, and the role of denitrifying bacteria in returning nitrogen to the atmosphere. This detailed explanation of the cycle’s processes is essential for understanding how nitrogen sustains life and impacts ecosystems.

Takeaways

• 😀 Nitrogen fixation is a process where atmospheric nitrogen (N₂) is converted into ammonia (NH₃), making it accessible to plants.
• 🌱 Rhizobium bacteria in leguminous plants play a crucial role in fixing nitrogen through symbiosis, helping plants absorb nitrogen.
• 💡 Free-living bacteria, such as cyanobacteria, also fix nitrogen in the soil, contributing to the nitrogen cycle independently.
• ⚡ Lightning can break nitrogen molecules (N₂) and convert them into nitrogen oxides, which also contribute to nitrogen fixation.
• 🔄 Nitrification is the process where ammonia (NH₃) is oxidized into nitrite (NO₂⁻) by *Nitrosomonas* bacteria, followed by its conversion into nitrate (NO₃⁻) by *Nitrobacter* bacteria.
• 🌿 Plants absorb nitrates (NO₃⁻) from the soil to synthesize proteins and other important compounds.
• 🐄 Animals obtain nitrogen by consuming plants or other animals, incorporating it into their bodies for various biological functions.
• 🔁 Denitrification is the process in which nitrate (NO₃⁻) is converted back into nitrogen gas (N₂) by denitrifying bacteria, completing the nitrogen cycle.
• ⚙️ Decomposers, such as bacteria and fungi, break down dead organisms and release ammonia (NH₃) back into the soil, recycling nitrogen.
• 🧬 Nitrogen is a vital element for life, being a core component of amino acids, proteins, and nucleic acids (DNA/RNA).
• 📚 Understanding the nitrogen cycle is essential for ecology and agriculture, as it ensures the continuous availability of nitrogen for plants and animals.

Q & A

What is the nitrogen cycle and why is it important?

The nitrogen cycle describes the movement of nitrogen through the ecosystem. It is crucial because nitrogen is a key element in amino acids, proteins, and DNA, but most organisms cannot use atmospheric nitrogen directly. The nitrogen cycle makes nitrogen available to plants and animals by converting it into usable forms like ammonia and nitrates.

What is nitrogen fixation, and which organisms are responsible for it?

Nitrogen fixation is the process of converting atmospheric nitrogen (N₂) into a usable form, such as ammonia (NH₃). This process is carried out by nitrogen-fixing bacteria, such as **Rhizobium** (found in legume plant roots) and **cyanobacteria**, which help convert nitrogen into a form plants can absorb.

How do legumes benefit from nitrogen fixation?

Legumes have a mutualistic relationship with nitrogen-fixing bacteria like **Rhizobium**. The bacteria reside in the roots of the plants and fix nitrogen from the atmosphere into ammonia, which the plant can use to grow. In return, the plant provides carbohydrates to the bacteria for energy.

What is nitrification, and which bacteria are involved in this process?

Nitrification is the process in which ammonia (NH₃) is converted into nitrites (NO₂⁻) and then into nitrates (NO₃⁻), a form of nitrogen that plants can absorb. The process is carried out by two groups of bacteria: **Nitrosomonas** converts ammonia to nitrites, and **Nitrobacter** further converts nitrites into nitrates.

Why are nitrates important for plants?

Nitrates are important because they are the form of nitrogen most easily absorbed by plants. Plants use nitrates to synthesize proteins and other essential molecules necessary for their growth and development.

What is denitrification, and which bacteria are involved?

Denitrification is the process by which bacteria convert nitrates (NO₃⁻) back into nitrogen gas (N₂), which is released into the atmosphere. This process is carried out by denitrifying bacteria, such as **Pseudomonas** and **Clostridium**, and it completes the nitrogen cycle.

What is the role of decomposers in the nitrogen cycle?

Decomposers, like fungi and bacteria, break down dead plants and animals, releasing nitrogen from their proteins and nucleic acids back into the soil in the form of ammonia (NH₃). This ammonia can then be used in nitrogen fixation or nitrification, continuing the cycle.

How does lightning contribute to the nitrogen cycle?

Lightning helps fix nitrogen by causing nitrogen molecules (N₂) in the atmosphere to react with oxygen, forming nitrogen oxides. These nitrogen oxides then dissolve in rainwater, converting into nitrates that are deposited in the soil, where plants can use them.

What would happen if denitrification did not occur in the nitrogen cycle?

If denitrification did not occur, nitrogen would accumulate in the soil as nitrates, which could lead to an imbalance in the nitrogen cycle. Excess nitrates could cause environmental issues, like water pollution (eutrophication) or an overabundance of nitrogen in the soil, which may harm plants and disrupt ecosystems.

How does the nitrogen cycle support ecosystems and biodiversity?

The nitrogen cycle supports ecosystems by ensuring a continuous supply of nitrogen, a vital nutrient for plant growth. Plants are at the base of the food chain, and animals depend on plants for food. By recycling nitrogen, the cycle helps maintain biodiversity by providing all organisms with the nitrogen they need to survive.