Which cell-organellae absent in neurons?

Options

A. Mitochondria
B. Ribosome
C. Centriole
D. Nucleus

Answer

To determine which cell organelle is absent in neurons, we can analyze the options provided: mitochondria, ribosomes, centrioles, and nucleus.

### Step-by-Step Solution:

1. **Identify the organelles present in neurons**:
- **Mitochondria**: Neurons require a significant amount of energy to function, and mitochondria are known as the powerhouses of the cell, providing ATP. Therefore, mitochondria are present in neurons.
- **Ribosomes**: These organelles are responsible for protein synthesis. Neurons also require proteins for various functions, including neurotransmitter production, so ribosomes are present in neurons.
- **Nucleus**: The nucleus contains the genetic material and controls cellular activities. Neurons have a nucleus as it is essential for maintaining cellular functions and gene expression.

2. **Examine the role of centrioles**:
- **Centrioles**: These are involved in cell division, specifically in the formation of the spindle fibers that separate chromosomes. They are typically found in cells that undergo mitosis.
- **Neurons and Cell Division**: Neurons are generally considered post-mitotic, meaning they do not divide after they have matured. As a result, they do not require centrioles for cell division.

3. **Conclude the answer**:
- Since centrioles are not necessary for neurons because they do not divide, we can conclude that the organelle absent in neurons is **centrioles**.

### Final Answer:
The cell organelle that is absent in neurons is **centrioles**.

---