The big idea: The Golgi apparatus processes proteins made on the rough ER and packs them into vesicles for secretion.
The points to remember
- The Golgi apparatus is a stack of flattened, curved membrane sacs, with vesicles at its edges.
- Vesicles from the rough ER bring new protein and fuse with one side of the stack.
- As the protein passes through, it is processed: for example, sugar chains are added (glycoproteins).
- On the other side, the finished protein is packed into secretory vesicles.
- These fuse with the plasma membrane and release the protein (exocytosis).
Remember it as: Rough ER makes it, the Golgi finishes and ships it.
Real example: mucus: Goblet cells in the lining of the gut and airways have a large Golgi apparatus. It adds many sugar chains to the protein mucin before it is secreted as mucus.
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How it is asked: Expect it inside a data question on labelled amino acids (the evidence that protein moves to the Golgi), a one-mark name of the organelle needed for secretion, or a short Describe of what the Golgi does.
IB-style questionOutline[1 mark]
A graph shows the percentage of labelled protein in the rough ER (X) and in the Golgi apparatus over time. Outline the evidence that the protein moves from X to the Golgi apparatus.
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See the answer broken into clear points, with guidance on how each point earns marks.
A three-mark Describe, in the Paper 2 style:
IB-style questionDescribe[3 marks]
Describe the role of the Golgi apparatus in a cell that secretes a protein.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.