Organelles & the Production of Proteins
- Inside 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 process of protein synthesis involves the following stages
- 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 number 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 (e.g. hydrolytic enzymes) or delivered to other 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 by the process of exocytosis
Many organelles are involved in the production and secretion of proteins
