Protein synthesis in bacteria, archaea, and other organisms lacking a nucleus occurs within the cytoplasm. Ribosomes, the molecular machines responsible for polypeptide assembly, are not compartmentalized within membrane-bound organelles. Therefore, the genetic code transcribed from DNA into messenger RNA (mRNA) is directly accessed by ribosomes present in the cellular fluid.
This spatial arrangement enables a tight coupling between transcription and translation. Because no nuclear membrane separates the processes, ribosomes can begin synthesizing proteins even before mRNA transcription is complete. This proximity enhances the speed and efficiency of gene expression, allowing prokaryotic cells to respond rapidly to environmental changes. This is a fundamental distinction from eukaryotic systems, where transcription occurs in the nucleus and translation in the cytoplasm.
