The role of RNA in protein synthesis is extremely important as protein synthesis could not occur without RNA. Three forms of RNA exist solely to create proteins. Through a process known as translation, RNA constructs the proteins necessary to sustain life. RNA plays a role in every step of translation, acting as the template for protein synthesis and gathering the necessary components to construct proteins.
RNA exists in all living organisms; it is a disposable copy of the genetic instructions held within DNA. Cells create RNA through a process known as transcription. The temporary unzipping of the DNA double helix allows for RNA polymerase to make a single strand of RNA that has the instructions for protein synthesis. In eukaryotic organisms, which are almost all living organisms, RNA leaves the cell nucleus before beginning translation. In organisms known as prokaryotes, which lack a cell nucleus, transcription and translation take place simultaneously side by side.
The role of RNA in protein synthesis begins when transcription ends and the genetic instructions for translation are ready. This strand of RNA, known as messenger RNA (mRNA), binds to the ribosome, an organelle within the cell. The ribosome is made of a molecule known as ribosomal RNA (rRNA). rRNA acts as a "factory floor" where protein synthesis can occur. With rRNA and mRNA joined together, translation can take place.
Once the strand of mRNA has attached to a molecule of rRNA on the ribosome, a third RNA molecule, transfer RNA (tRNA), plays a role in protein synthesis. Many tRNA molecules collect the necessary amino acids already present within the cell's cytoplasm. Following the instructions set forth by the strand of mRNA, tRNA molecules put the amino acids into the correct place on the protein. The growing protein starts off as a long polypeptide chain before it begins to fold over on itself. This process of folding creates a complex three-dimensional shape dictated by the mRNA's instructions.
The role of RNA in protein synthesis has other facets as well. Besides the instructions to create a protein, mRNA also carries the instructions to begin and end protein synthesis. These markers in the genetic code are known as the start and stop codons, a unique series of three base pairs. The other possible combinations of base pairs code for specific amino acids. This simple process of RNA in protein synthesis has a twofold benefit: translation runs quickly and there is a lower chance of making a mistake in the growing protein.
To protect against the production of faulty proteins, the RNA in protein synthesis has built-in safeguards to correct against mistakes. This job is the responsibility of rRNA and the surrounding ribosome. If a mistake occurs, the ribosome detaches the incorrect amino acid and waits until a molecule of tRNA delivers the correct amino acid. The process of translation then continues on uninhibited.