Science
Translation.
Definition
The process by which ribosomes decode the mRNA sequence to assemble a specific chain of amino acids, forming a protein. It takes place on ribosomes in the cytoplasm and involves mRNA, tRNA, and amino acids working together.
How it works · 6 phases
Step by step.
- The small ribosomal subunit binds to the mRNA and locates the start codon (AUG).
- An initiator tRNA carrying methionine pairs with the start codon at the P site.
- The large ribosomal subunit joins, and a second tRNA enters the A site matching the next codon.
- A peptide bond forms between amino acids, and the ribosome translocates one codon forward.
- This elongation cycle repeats as new tRNAs deliver amino acids codon by codon.
- When a stop codon (UAA, UAG, or UGA) enters the A site, release factors terminate translation and the polypeptide is released.
Examples
Real-world.
- 1 Ribosomes on the rough ER translating mRNA to produce secretory proteins like antibodies
- 2 Free ribosomes in the cytoplasm translating mRNA for cytoplasmic enzymes
- 3 Polyribosomes (multiple ribosomes on one mRNA) producing many copies of the same protein simultaneously
Key Fact
Each codon (3 mRNA bases) codes for one amino acid. AUG = start codon (methionine); UAA, UAG, UGA = stop codons.