Final answer:
Three types of RNA - messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA) - play roles in protein synthesis within cells.
Step-by-step explanation:
Three types of RNA are involved in protein synthesis within cells - messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). Each type of RNA plays a specific role in the process. mRNA carries the genetic instructions from DNA to the ribosomes, tRNA brings amino acids to the ribosomes, and rRNA helps form the ribosomes where protein synthesis occurs.