The Protein Synthesis Pathway
Organelles do not work in isolation โ they form a production line for making and exporting proteins. Here is how the key organelles cooperate:
- Nucleus: The DNA in the nucleus contains the instructions for making a specific protein. A section of DNA is transcribed (copied) into a molecule called messenger RNA (mRNA). The mRNA exits the nucleus through nuclear pores.
- Ribosomes: The mRNA travels to a ribosome, which reads the mRNA code and assembles amino acids into a polypeptide chain โ this is called translation. The ribosome is the actual "builder" of the protein, and folds the new protein into its correct 3D shape.
- Golgi Apparatus: Transport vesicles carrying the newly made protein fuse with the Golgi apparatus. Here the protein is chemically modified (e.g. sugar groups are added), quality-checked, and packaged into secretory vesicles.
- Vesicle Transport: Secretory vesicles bud off from the Golgi and travel to the cell membrane. They fuse with the membrane and release the protein outside the cell โ this is called exocytosis.
This pathway โ Nucleus โ Ribosome โ Golgi โ Vesicle โ Cell membrane โ is how all secreted proteins (e.g. enzymes, hormones like insulin) are made and exported. Cells that secrete lots of proteins (e.g. pancreatic cells making insulin) have very active Golgi apparatus and many mitochondria to power protein production.
Grade 7-9 Detail
This how it works covers How Do Organelles Work Together? within Cell Organelles for GCSE Biology. Revise Cell Organelles in Cell Biology for GCSE Biology with 12 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 6 of 14 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Cell Organelles
Scientists studying mitochondria use electron microscopes rather than light microscopes. Which statement correctly explains why electron microscopes are more useful for studying cell ultrastructure?
The diameter of a ribosome is approximately 0.00002 mm. (a) Write this diameter in standard form, in millimetres. (b) Convert this diameter into nanometres (nm).