Protein synthesis does not occur in the axon because 

Options

A. cytoplasm is absent
B. SER is absent
C. Nissl granules are absent
D. it is efferent fibre

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks why protein synthesis does not occur in the axon of a neuron. To answer this, we need to analyze the structures involved in protein synthesis and their presence or absence in the axon.

2. **Analyzing the Options**:
- **Option A: Cytoplasm is absent**: The axon does contain cytoplasm, so this option is incorrect.
- **Option B: Smooth Endoplasmic Reticulum (SER) is absent**: While SER is involved in lipid synthesis, it is not directly responsible for protein synthesis. Therefore, this option is also incorrect.
- **Option C: Nissl granules are absent**: Nissl granules, which are composed of rough endoplasmic reticulum and ribosomes, are essential for protein synthesis. Their absence in the axon is a key reason why protein synthesis does not occur there.
- **Option D: It is an efferent fiber**: The classification of the axon as an efferent fiber (which transmits signals away from the neuron) does not affect its ability to synthesize proteins. Thus, this option is incorrect.

3. **Conclusion**: The correct answer is that protein synthesis does not occur in the axon because Nissl granules are absent. Nissl granules are crucial for protein synthesis, and their absence in the axon is the primary reason for the lack of protein synthesis in this part of the neuron.

**Final Answer**: Protein synthesis does not occur in the axon because Nissl granules are absent.

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