Nitrogenase:

Options

A. Is a Cu - Fe protein
B. Is present in all Prokaryotes
C. Can convert `NH_(3)` into `N_(2)`
D. Is very sensitive to `O_(2)`

Answer

### Step-by-Step Solution:

1. **Understanding Nitrogenase**: Nitrogenase is an enzyme that plays a crucial role in nitrogen fixation, which is the process of converting atmospheric nitrogen (N₂) into ammonia (NH₃). This process is essential for making nitrogen available to living organisms.

**Hint**: Remember that nitrogen fixation is the conversion of atmospheric nitrogen into a usable form for plants.

2. **Composition of Nitrogenase**: The enzyme nitrogenase is composed of iron and molybdenum, not copper. It is found in certain prokaryotes, particularly in nitrogen-fixing bacteria.

**Hint**: Focus on the correct metal components of nitrogenase; it is important to differentiate between molybdenum and copper.

3. **Function of Nitrogenase**: The primary function of nitrogenase is to catalyze the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃). This ammonia can then be utilized by plants for growth.

**Hint**: Keep in mind that nitrogenase facilitates the transformation of nitrogen gas into ammonia, which is a key nutrient for plants.

4. **Sensitivity to Oxygen**: Nitrogenase is highly sensitive to molecular oxygen (O₂). Exposure to oxygen can inhibit its function, which is why nitrogen-fixing bacteria often have mechanisms to protect the enzyme from oxygen.

**Hint**: Remember that nitrogenase cannot function properly in the presence of oxygen; this is a critical characteristic of the enzyme.

5. **Role of L-hemooglobin**: To protect nitrogenase from oxygen, some nitrogen-fixing bacteria produce a protein called L-hemooglobin. This protein acts as an oxygen scavenger, helping to create a low-oxygen environment for nitrogenase to function.

**Hint**: Consider the protective mechanisms that bacteria have developed to ensure nitrogenase can work effectively in aerobic conditions.

6. **Types of Nitrogen-Fixing Bacteria**: There are two main types of nitrogen-fixing bacteria: symbiotic (those that form relationships with plants, like legumes) and free-living (those that do not require a host plant).

**Hint**: Differentiate between symbiotic and free-living nitrogen-fixing bacteria and their ecological roles.

### Summary:
Nitrogenase is an enzyme that converts atmospheric nitrogen into ammonia, is composed of iron and molybdenum, and is highly sensitive to oxygen. L-hemooglobin helps protect nitrogenase from oxygen, and there are both symbiotic and free-living nitrogen-fixing bacteria.