RNA processing is a crucial step that occurs exclusively in eukaryotic organisms, distinguishing them from prokaryotic organisms. This process involves two significant modifications to the premature mRNA (pre-mRNA) that occur at both ends of the molecule. The first modification is the addition of a 5' cap, which is a modified guanine nucleotide attached to the 5' end of the pre-mRNA. The second modification involves the addition of a poly A tail, a sequence composed of multiple adenine nucleotides added to the 3' end of the pre-mRNA.

These modifications serve several essential functions. Firstly, both the 5' cap and the poly A tail facilitate the export of mRNA from the nucleus, where it is transcribed, to the cytoplasm, where translation occurs. This export is vital for the mRNA to be translated into proteins. Secondly, these modifications protect the mRNA from degradation by enzymes that could potentially break down the RNA. Lastly, the 5' cap and poly A tail are critical for the attachment of ribosomes to the mRNA, which is necessary for the translation process. Ribosomes are the cellular structures responsible for synthesizing proteins based on the mRNA sequence.

In summary, RNA processing, through the addition of the 5' cap and poly A tail, not only prepares the mRNA for translation but also ensures its stability and successful export from the nucleus to the cytoplasm.