OCR A Level Biology:复习笔记2.1.7 Organelles & the Production of Proteins

Organelles & the Production of Proteins

  • In cells, many organelles are involved in the production and secretion of proteins
  • Organelles are specialised parts of a cell that carry out a particular function
    • Some organelles are membrane-bound

     

  • The organelles involved in protein synthesis include:
    • Nucleus
    • Ribosomes
    • Rough endoplasmic reticulum (RER)
    • Golgi apparatus
    • Cell surface membrane

     

  • The nucleus stores the DNA (that codes for the production of proteins) and also contains the nucleolus, which manufactures ribosomes (required for protein synthesis)
    • The DNA from the nucleus is copied into a molecule of mRNA via a process known as transcription

     

  • The mRNA strand leaves the nucleus through a nuclear pore and attaches to a ribosome on the rough endoplasmic reticulum
    • The ribosome 'reads' the genetic instructions contained within the mRNA and uses this code to synthesise a protein via a process known as translation
    • This protein then passes into the lumen (the inside space) of the rough endoplasmic reticulum to be folded and processed
    • Cells that produce a large amount of proteins (e.g. enzyme or hormone-producing cells) have an extensive rough endoplasmic reticulum

     

  • The processed proteins are then transported to the Golgi apparatus (also known as the Golgi body or Golgi complex) in vesicles, which fuse with the Golgi apparatus, releasing the proteins
    • The Golgi apparatus modifies the proteins, preparing them for secretion
    • Proteins that go through the Golgi apparatus are usually exported (e.g. hormones such as insulin), put into lysosomes (such as hydrolytic enzymes) or delivered to other membrane-bound organelles
    • The modified proteins then leave the Golgi apparatus in vesicles

     

  • Finally, these vesicles (containing the final proteins) fuse with the cell surface membrane, releasing the proteins

Many organelles are involved in the production and secretion of proteins

 

 

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