Protein synthesis, the process by which cells generate proteins, differs in prokaryotes and eukaryotes due to several factors related to their cellular structures and mechanisms. Prokaryotes, such as bacteria, lack a distinct nucleus and other membrane-bound organelles, while eukaryotes, including plants, animals, and fungi, have a well-defined nucleus and various organelles. This difference affects the localization and regulation of protein synthesis. In prokaryotes, transcription (the synthesis of RNA from DNA) and translation (the synthesis of proteins from RNA) are coupled, meaning they occur simultaneously. The mRNA transcript is rapidly translated into protein by ribosomes as it is being synthesized. In contrast, eukaryotes separate transcription and translation in time and space. Transcription occurs inside the nucleus, and the mRNA is then processed, modified, and transported to the cytoplasm, where translation takes place. Eukaryotic mRNA undergoes various modifications before it can be translated into protein. This includes the addition of a 5' cap and a poly(A) tail, as well as the removal of introns through a process called splicing. These modifications provide stability, facilitate transport to the cytoplasm, and allow for the production of multiple protein isoforms. Prokaryotes do not typically undergo extensive mRNA processing. Prokaryotic and eukaryotic ribosomes differ in size and composition. Prokaryotes have smaller ribosomes (70S) composed of a 30S and a 50S subunit, while eukaryotes have larger ribosomes (80S) consisting of a 40S and a 60S subunit. These structural differences impact the initiation, elongation, and termination of protein synthesis. Eukaryotes possess more complex mechanisms for regulating gene expression compared to prokaryotes. Eukaryotic gene expression is regulated at multiple levels, including transcriptional control, post-transcriptional modifications, and translational control. This allows for fine-tuning of protein synthesis in response to various internal and external signals. Prokaryotes primarily regulate gene expression at the transcriptional level.
Overall, the differences in protein synthesis between prokaryotes and eukaryotes are rooted in their distinct cellular organization, mechanisms of gene expression, and the need for eukaryotes to coordinate protein synthesis within a more complex and compartmentalized cellular environment.