The Golgi apparatus processes proteins received from the rough endoplasmic reticulum, then sorts and packages them into vesicles for transport within the cell or secretion by exocytosis. This is additional higher level (AHL) content in IB Biology subtopic B2.2, Organelles and compartmentalization.
How the Golgi Apparatus Works
- Ribosomes attached to the rough endoplasmic reticulum (rER) synthesize proteins intended for transport within the cell or secretion.
- The proteins enter the rER and are carried in transport vesicles to the Golgi apparatus.
- These vesicles fuse with the receiving side of the Golgi apparatus, adding their contents and membrane.
- As proteins pass through the Golgi apparatus, they are processed. This may include modification of attached carbohydrate groups, producing glycoproteins with forms suited to their destinations and functions.
- The Golgi sorts the processed proteins and packages them into new vesicles.
- These vesicles move to specific destinations. Some fuse with the plasma membrane and release proteins by exocytosis; others deliver proteins to locations within the cell.
The Golgi apparatus consists of stacks of flattened membrane sacs. This compartmentalization concentrates proteins and processing enzymes, allowing sequential processing before proteins are dispatched.
A common misconception is that the Golgi apparatus synthesizes proteins. It does not: ribosomes perform protein synthesis. The Golgi receives proteins made on rER-bound ribosomes and processes, sorts and packages them. Another misconception is that all Golgi vesicles leave the cell; many instead transport proteins within the cell.
Exam Technique
For an outline question, state the sequence: rER-bound ribosomes synthesize proteins → transport vesicles carry them to the Golgi → the Golgi processes and packages them → vesicles transport or secrete them. For an explain question, link the Golgi’s stacked, membrane-bound compartments to concentration of enzymes and ordered protein processing. Avoid saying only that it “packages substances”; identify proteins, vesicles and their destinations.