Which step of protein synthesis is performed by the ribosomes ?

Options

A. Assemble amino acids in a chain
B. Carry a copy of a gene to the cytoplasm
C. Contain the code for thee synthesis of a protein
D. Determine the order of bases in the protein

Answer

**Step-by-Step Solution:**

1. **Understanding Protein Synthesis**: Protein synthesis occurs in two main stages: transcription and translation. Transcription involves the synthesis of mRNA from DNA, while translation is the process where ribosomes synthesize proteins based on the mRNA sequence.

2. **Role of Ribosomes**: Ribosomes are the cellular machinery responsible for translating the mRNA into a polypeptide chain, which then folds into a functional protein. This process is known as translation.

3. **Translation Process**: During translation, ribosomes read the sequence of the mRNA in sets of three nucleotides (codons). Each codon corresponds to a specific amino acid.

4. **Ribosome Structure**: Ribosomes consist of two subunits (large and small). In prokaryotes, the large subunit is referred to as 50S and the small subunit as 30S. These subunits come together during translation.

5. **Amino Acid Assembly**: The ribosome has three sites: the A (aminoacyl) site, the P (peptidyl) site, and the E (exit) site. The ribosome facilitates the binding of tRNA molecules, which carry amino acids to the ribosome. The ribosome catalyzes the formation of peptide bonds between the amino acids, effectively assembling them into a polypeptide chain.

6. **Conclusion**: The primary function of the ribosome in protein synthesis is to assemble amino acids into a chain, forming a protein.

**Final Answer**: The step of protein synthesis performed by the ribosomes is translation, specifically the assembly of amino acids into a polypeptide chain.

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