Translation

Science

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

  1. The small ribosomal subunit binds to the mRNA and locates the start codon (AUG).
  2. An initiator tRNA carrying methionine pairs with the start codon at the P site.
  3. The large ribosomal subunit joins, and a second tRNA enters the A site matching the next codon.
  4. A peptide bond forms between amino acids, and the ribosome translocates one codon forward.
  5. This elongation cycle repeats as new tRNAs deliver amino acids codon by codon.
  6. When a stop codon (UAA, UAG, or UGA) enters the A site, release factors terminate translation and the polypeptide is released.

Examples

  • Ribosomes on the rough ER translating mRNA to produce secretory proteins like antibodies
  • Free ribosomes in the cytoplasm translating mRNA for cytoplasmic enzymes
  • 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.

Related Terms

Transcription Transcription and translation Macromolecules Enzyme structure

Study This Concept

Practice translation with free review games in these units:

AP Biology Unit 6: Gene Expression and Regulation