Revision Notes

17.1.3 Protein Synthesis

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Protein synthesis, IGCSE & GCSE Biology revision notesProtein synthesis


  • Proteins are made by ribosomes with the sequence of amino acids controlled by the sequence of bases contained within DNA
  • DNA cannot travel out of the nucleus to the ribosomes (it is far too big to pass through a nuclear pore) so the base code of each gene is transcribed onto an RNA molecule called messenger RNA (mRNA).
  • mRNA then moves out of the nucleus and attaches to a ribosome
  • The ribosome ‘reads’ the code on the mRNA in groups of three
  • Each triplet of bases codes for a specific amino acid
  • In this way the ribosome translates the sequence of bases into a sequence of amino acids that make up a protein
  • Once the amino acid chain has been assembled, it is released from the ribosome so it can fold and form the final structure of the protein


How ribosomes build proteins, IGCSE & GCSE Biology revision notes

 The triplet code of DNA (carried by mRNA) is read by the ribosome and amino acids are attached together in a specific sequence to form the protein


  • In this way, DNA controls cell function by controlling the production of proteins
  • The proteins may be enzymes, antibodies, or receptors for neurotransmitters
  • Although all body cells in an organism contain the same genes, many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.

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