Protein synthesis is a fundamental biological process that occurs in all living cells, involving several key stages: transcription, RNA processing, and translation.
1. Transcription: This is the first step where the DNA inside the cell’s nucleus serves as a template to create messenger RNA (mRNA). The enzyme RNA polymerase binds to a specific region of the DNA, unwinding the double helix and synthesizing a single strand of RNA. The mRNA molecule carries the genetic information from the DNA to the ribosomes, which are the cellular machinery for protein synthesis.
2. RNA Processing: After transcription, the newly formed mRNA undergoes several modifications. These include the addition of a 5′ cap and a poly-A tail at the 3′ end. Additionally, introns (non-coding regions) are removed through a process called splicing, resulting in a mature mRNA that contains only exons (coding regions). This mature mRNA then exits the nucleus and enters the cytoplasm.
3. Translation: In the cytoplasm, ribosomes read the sequence of the mRNA in sets of three nucleotides called codons. Each codon specifies a particular amino acid. Transfer RNA (tRNA) molecules, which carry amino acids, match their anticodons with the codons on the mRNA. As the ribosomes move along the mRNA, amino acids are linked together in the order specified by the mRNA sequence, forming a polypeptide chain. Eventually, the chain folds into a functional protein.
In summary, the pathway for protein synthesis involves a coordinated sequence of events that starts with transcription of DNA into mRNA, followed by processing of the mRNA, and concludes with translation at the ribosome, culminating in the formation of proteins essential for cellular function.