Final answer:
The statement that a polyribosome is a single mRNA that is translated by many ribosomes at one time is true. Polyribosomes increase the efficiency of protein synthesis by allowing multiple ribosomes to translate one mRNA strand concurrently.
Step-by-step explanation:
The statement is true: A polyribosome, also known as a polysome, is a complex comprising a single mRNA molecule that is being concurrently translated by many ribosomes. This efficient system speeds up the protein synthesis process. Polyribosomes allow multiple ribosomes to assemble along the mRNA strand and synthesize the same protein simultaneously, effectively increasing the volume of protein production relative to time.
In prokaryotes, transcription and translation can occur simultaneously which further expedites protein production as multiple ribosomes attach to the emerging mRNA strand before transcription is even complete. However, in eukaryotic cells, this process cannot start until RNA synthesis is finished and the mRNA is transferred out of the nucleus. Despite this difference, polyribosomes are a feature common to both types of cells, highlighting a key aspect of the cellular machinery dedicated to protein synthesis.