In a polyribosome complex, the ribosome present towards 5'end of mRNA has

Options

A. longest polypeptide chain
B. smallest chain of polypeptide
C. all ribosomes have polypeptide chains of equal size
D. a chain without 'met'

Answer

To answer the question about the polyribosome complex and the ribosome present towards the 5' end of mRNA, we can break down the solution into several steps:

### Step-by-Step Solution:

1. **Understanding Polyribosomes**:
- A polyribosome (or polysome) is a complex formed by multiple ribosomes translating a single mRNA strand simultaneously. This allows for the efficient synthesis of proteins.

2. **Orientation of mRNA**:
- mRNA has a specific orientation with a 5' end and a 3' end. The ribosomes attach to the mRNA at the 5' end and move towards the 3' end during translation.

3. **Ribosome Positioning**:
- In a polyribosome, the ribosome closest to the 5' end of the mRNA is the first ribosome to bind and start translating the mRNA.

4. **Polypeptide Chain Length**:
- The ribosome at the 5' end of the mRNA is synthesizing the initial part of the polypeptide chain. At this stage, the polypeptide chain is still short because translation has just begun.
- As ribosomes progress along the mRNA towards the 3' end, they continue to add amino acids to the growing polypeptide chain, resulting in longer chains.

5. **Conclusion**:
- Therefore, the ribosome present towards the 5' end of the mRNA will have the shortest polypeptide chain, as it is the first to start translation and has not yet added many amino acids.

### Final Answer:
In a polyribosome complex, the ribosome present towards the 5' end of mRNA has the **smallest polypeptide chain**.

---