Protein Synthesis

Protein Synthesis

Basics of Protein Synthesis

  • Protein synthesis is a two-step process involving transcription and translation.
  • It occurs in cells and is vital for the production of proteins needed for cell structure and function.


  • Transcription occurs in the nucleus where the DNA unzips, and one strand is used as a template to synthesise RNA.
  • RNA polymerase links free RNA nucleotides together to form a strand of messenger RNA (mRNA).
  • Before mRNA leaves the nucleus, it undergoes splicing where introns (non-coding sequences) are removed and exons (coding sequences) are joined together.


  • Translation takes place at the ribosomes in the cytoplasm.
  • mRNA attaches itself to the ribosome where a protein is synthesised.
  • The sequence of bases on the mRNA determines the sequence of amino acids in the protein.
  • Each set of three bases (codon) on the mRNA corresponds to one amino acid.
  • Transfer RNA (tRNA) brings the correct amino acid to the ribosome in a process called elongation; the amino acids are joined together in a chain to form a protein.
  • The process stops when a stop codon is reached on the mRNA, marking the end of the protein chain.


  • Proteins are made up of one or more chains of amino acids, which determine their function and property.
  • The sequence of amino acids in a protein is determined by the sequence of bases in a gene on the DNA molecule.
  • The amino acid sequence determines the shape of the protein, and the shape of the protein determines its function.

Other Points

  • Mutations in the DNA can lead to an incorrect sequence of amino acids, which can lead to the formation of faulty proteins.
  • DNA codes for around 20 different amino acids, which can form a wide variety of sequences to create different proteins.
  • Understanding protein synthesis is fundamental for understanding genetic engineering, gene therapy, and the development therapeutic drugs.