What is the primary function of RNA in cells?

RNA plays a crucial role in the process of protein synthesis, serving as a template for translating genetic information into proteins. This is primarily accomplished through two main processes: transcription and translation. During transcription, messenger RNA (mRNA) is synthesized from a DNA template, carrying the genetic instructions out of the nucleus to the ribosomes. Once at the ribosomes, transfer RNA (tRNA) and ribosomal RNA (rRNA) are involved in translating the sequence of the mRNA into a polypeptide chain, which eventually folds into a functional protein.

This function of RNA as a template for protein synthesis highlights its importance in the central dogma of molecular biology, which outlines the flow of genetic information within a biological system. Other options do not align with RNA's primary role; for example, while DNA is responsible for storing genetic information, RNA acts in a more dynamic capacity during the expression of that information. Similarly, providing structure to the cell is mainly a function of proteins and complex biological structures, while the transportation of oxygen in the blood is primarily performed by hemoglobin found in red blood cells. Thus, the correct answer identifies RNA’s key function as a critical intermediary in the synthesis of proteins essential for cell and organismal function.