Problem 9 Discuss biological fixation of n... [FREE SOLUTION]

Chapter 33: Problem 9

Discuss biological fixation of nitrogen.

Short Answer

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Biological nitrogen fixation is the conversion of atmospheric nitrogen into a usable form like nitrate or ammonium by certain bacteria, primarily diazotrophs. These bacteria possess an enzyme nitrogenase, facilitating this conversion. Common organisms involved include the bacteria Rhizobium in root nodules and cyanobacteria in aquatic environments.

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Understanding Nitrogen fixation

Biological Nitrogen fixation is the process whereby atmospheric nitrogen is converted into a form that can be readily used by plants. It is called 'biological' as it is performed by living organisms, primarily certain bacteria.

Significance of Nitrogen fixation

Nitrogen is a vital nutrient required by plants for their growth, development, and reproduction. However, atmospheric nitrogen is in a form (N鈧� gas) that plants cannot directly utilize. Therefore, it needs to be 'fixed' or converted into a usable form like nitrate or ammonium.

Process of Biological Nitrogen fixation

This process is primarily carried out by free-living or symbiotic bacteria called diazotrophs. These bacteria have an enzyme called nitrogenase which allows them to convert atmospheric nitrogen into ammonia. This ammonia can then be incorporated into the biological macromolecules needed by the plant.

Role of Organisms

Different organisms play key roles in this process. For instance, nodules on plant roots house bacteria Rhizobium, which carry out nitrogen fixation. Cyanobacteria in water bodies also fix nitrogen.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Role of Nitrogenase

Nitrogenase is a crucial enzyme that enables the biological nitrogen fixation process. It is responsible for converting atmospheric nitrogen (N鈧�) into ammonia (NH鈧�), a form that plants can easily use. This enzyme is specifically found in microorganisms known as diazotrophs, which include certain bacteria and archaea.

Diazotrophs employ nitrogenase to break the strong triple bonds in nitrogen molecules, allowing the conversion process to occur. This is an energy-intensive process that requires ATP and reducing power. Despite the complexity of the task, nitrogenase efficiently facilitates this transformation, proving indispensable for life on Earth.

The efficiency of this enzyme is crucial since nitrogen makes up about 78% of the Earth's atmosphere, yet it is hard to access in its natural form.
Nitrogenase is sensitive to oxygen, so the environments where these bacteria live often have low oxygen levels, or the bacteria have mechanisms to protect the enzyme from oxygen.

Symbiotic Bacteria

Symbiotic bacteria play a pivotal role in the process of nitrogen fixation by forming partnerships with plants. One well-known example of such a partnership is between leguminous plants and Rhizobium bacteria. These bacteria reside within root nodules, where they convert nitrogen from the air into forms usable by the plant.

The symbiosis is mutually beneficial: the plant supplies carbohydrates and a hospitable environment to the bacteria, and in return, the bacteria provide the plant with essential nitrogen. This partnership is so vital that it significantly impacts soil health and fertility, making it invaluable in agriculture.

The bacteria receive energy in the form of carbohydrates from the plant, which are essential for the energy-demanding task of nitrogen fixation.
This relationship reduces the need for synthetic nitrogen fertilizers, providing an organic method to enrich the soil.

Importance of Nitrogen for Plants

Nitrogen is essential for plant life, acting as a key building block of amino acids, proteins, nucleic acids, and chlorophyll. These components are crucial for plant growth, development, and reproduction. However, atmospheric nitrogen is in an inert form that plants cannot directly utilize, which is why the process of nitrogen fixation is so important.

Without nitrogen, plants would be unable to produce the proteins necessary for enzyme function and structure. Moreover, nitrogen is a component of chlorophyll, the green pigment in plants responsible for photosynthesis, the process through which plants convert sunlight into energy.

Plants acquire nitrogen mainly in the form of ammonium (NH鈧勨伜) or nitrate (NO鈧冣伝), both of which are directly usable forms.
Ammonium is often directly assimilated into amino acids, whereas nitrate is usually reduced to ammonium before incorporation.
Healthy growth, lush green foliage, and reproductive success all depend on adequate nitrogen supply.

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Discuss biological fixation of nitrogen.

Short Answer

Step by step solution

Understanding Nitrogen fixation

Significance of Nitrogen fixation

Process of Biological Nitrogen fixation

Role of Organisms

Key Concepts

Role of Nitrogenase

Symbiotic Bacteria

Importance of Nitrogen for Plants

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