Production of proteins

• Organelles


  • Some are membrane-bound
• Organelles involved in protein synthesis

  • Nucleus
  • Ribosomes
  • Rough endoplasmic reticulum (RER)
  • Golgi apparatus
  • Cell surface membrane
• Nucleus


  Stores the DNA (that codes for the production of proteins) and contains the nucleolus, which manufactures ribosomes (required for protein synthesis)
• Protein synthesis


  1. DNA from the nucleus is copied into mRNA via transcription

  2. mRNA strand leaves the nucleus and attaches to a ribosome on the rough endoplasmic reticulum

  3. Ribosome reads the genetic instructions in mRNA and uses this code to synthesise a protein via translation

  4. Protein passes into the lumen of the rough endoplasmic reticulum to be folded and processed

  5. Processed proteins are transported to the Golgi apparatus in vesicles

  6. Golgi apparatus modifies the proteins, preparing them for secretion

  7. Modified proteins leave the Golgi apparatus in vesicles

  8. Vesicles fuse with the cell surface membrane, releasing the proteins by exocytosis
• Cells that produce a large number of proteins

  • Have an extensive rough endoplasmic reticulum
• Proteins that go through the Golgi apparatus are usually exported (e.g. hormones such as insulin), put into lysosomes (e.g. hydrolytic enzymes) or delivered to other organelles
• The nucleolus manufactures ribosomes for protein synthesis in the rough endoplasmic reticulum
• The nucleus manufactures mRNA, which is needed by ribosomes to make proteins
• The ribosomes in the rough endoplasmic reticulum make proteins
• The rough endoplasmic reticulum processes the proteins which are then sent in vesicles to the Golgi body
• The Golgi body further processes the proteins and sends them in vesicles to the plasma membrane
• The vesicles fuse with the plasma membrane to secrete the finished protein product