Select the CORRECTLY matched pair.

Options

A. Ribozyme - part of smaller subunit of ribosome
B. P-site - Contributed by two ribosomal subunits
C. E-site - Face the tunnel between two subunits of ribosome
D. A-site - Part of smaller subunit of ribosome facing the tunnel site

Answer

To solve the question "Select the CORRECTLY matched pair," we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Ribozyme**:
- A ribozyme is a type of RNA that can act as an enzyme. The specific ribozyme involved in protein synthesis is the peptidyl transferase.
- **Hint**: Remember that ribozymes are RNA molecules with catalytic activity.

2. **Identifying the Location of Peptidyl Transferase**:
- Peptidyl transferase is found in the larger subunit of the ribosome, not the smaller subunit. Therefore, any statement claiming it is part of the smaller subunit is incorrect.
- **Hint**: Always check the structural components of ribosomes and their functions.

3. **Examining the P-site**:
- The P-site (peptidyl site) is indeed formed by both the large and small ribosomal subunits. This site holds the tRNA carrying the growing polypeptide chain during translation.
- **Hint**: Recall the roles of the different sites in the ribosome: P, A, and E.

4. **Reviewing the E-site**:
- The E-site (exit site) is part of the larger subunit of the ribosome and is where the tRNA exits after delivering its amino acid. It does not involve the smaller subunit.
- **Hint**: The E-site is specifically for tRNA exit, so it is crucial to know which subunit it belongs to.

5. **Analyzing the A-site**:
- The A-site (aminoacyl site) is also located on the larger subunit of the ribosome. It is where the incoming aminoacyl-tRNA binds during protein synthesis.
- **Hint**: The A-site is crucial for the addition of new amino acids to the growing polypeptide chain.

6. **Conclusion**:
- Based on the analysis, the correct statement is that the P-site is formed by both ribosomal subunits. Therefore, the correctly matched pair is the P-site.

### Final Answer:
The correct answer is the P-site, which is formed by both the larger and smaller ribosomal subunits.