CIE IGCSE Biology: 复习笔记:17.1.4 Protein Synthesis

CIE IGCSE Biology: 复习笔记:17.1.4 Protein Synthesis

Transcription & Translation: Extended

 

Protein-synthesisProtein 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

 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

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