OCR A Level Biology:复习笔记2.1.7 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