Which cellular structure is responsible for protein synthesis?

The cellular structure primarily responsible for protein synthesis is ribosomes. Ribosomes are complex molecular machines found within all living cells that facilitate the translation of messenger RNA (mRNA) into proteins. This process occurs in two main stages: initiation and elongation, where ribosomes read the sequence of mRNA and assemble amino acids into a polypeptide chain according to the genetic instructions.

While the endoplasmic reticulum plays a significant role in the processing and modification of proteins after they have been synthesized by ribosomes, it does not itself synthesize proteins. The nucleus is involved in the transcription of DNA into mRNA but does not carry out the actual synthesis of proteins. Mitochondria are primarily known for energy production through cellular respiration and do not have a direct role in protein synthesis.

By understanding the role of ribosomes in the process, it becomes clear why they are considered the primary site of protein synthesis within the cell.