Where does the process of translation (polypeptide synthesis) occur in a cell?

Translation, the process through which polypeptides (or proteins) are synthesized from messenger RNA (mRNA), occurs at the ribosome. Ribosomes are complex molecular machines found in all living cells, and they serve as the site where the genetic code carried by mRNA is translated into a chain of amino acids, ultimately folding into functional proteins.

While the nucleus is involved in the transcription of mRNA from DNA, and the endoplasmic reticulum can play a role in the synthesis of proteins that are secreted or inserted into membranes, it is important to note that the actual synthesis of the polypeptide occurs at the ribosome. The mitochondria, known mainly for their role in energy production, are not directly involved in the process of translating mRNA into proteins.

Therefore, the ribosome's crucial role in the translation process underlines why it is the correct answer in this context, as it directly facilitates the assembly of amino acids into protein chains based on the sequence coded in mRNA.