Which of the following compounds is used directly to build proteins

Options

A. `NH_(3)`
B. `N_(2)`
C. Nitrate
D. Nitrite

Answer

To solve the question, "Which of the following compounds is used directly to build proteins?", we can follow these steps:

### Step 1: Understand the Role of Nitrogen in Protein Synthesis
- Proteins are made up of amino acids, which contain nitrogen. Plants require nitrogen to synthesize these amino acids.

**Hint:** Remember that proteins are composed of amino acids, and nitrogen is a key component of amino acids.

### Step 2: Identify the Forms of Nitrogen Available to Plants
- Nitrogen in the atmosphere is not directly usable by plants. It needs to be converted into a form that plants can absorb. The two primary forms are ammonia (NH3) and nitrate (NO3-).

**Hint:** Consider the different forms of nitrogen and their availability to plants.

### Step 3: Understand the Process of Nitrogen Conversion
- Nitrogen from the atmosphere is converted into ammonia by nitrogen-fixing bacteria. Ammonia can then be converted into nitrate through a process called nitrification. Nitrate is the form that plants can absorb directly.

**Hint:** Think about the nitrogen cycle and how nitrogen is transformed into usable forms for plants.

### Step 4: Determine Which Compound is Directly Used for Protein Synthesis
- Among the options, nitrate (NO3-) is the form that plants absorb and use to synthesize amino acids, which are then used to build proteins.

**Hint:** Focus on which nitrogen compound is directly taken up by plants for protein synthesis.

### Step 5: Eliminate Incorrect Options
- Ammonia is not directly used to build proteins; it must first be converted to other forms. Nitrogen gas (N2) cannot be absorbed directly by plants. Therefore, the only correct option is nitrate.

**Hint:** Review the options carefully and eliminate those that do not lead to protein synthesis.

### Final Answer
The correct answer to the question is **nitrate (NO3-)**.