Let's discuss about an essay question.
PYQ:STPM 2018
Describe the pathway of amylase secretion in pancreatic cells. (8)
The question asks us to explain about PATHWAY,which is a process,from where to where.
1.We know amylase is an enzyme(globular protein) which is secreted by pancreatic cells.
2.To synthesise a protein,first we must have genetic information from DNA.
Now your knowledge about organelles comes in.
1. In nucleus,transcription occurs to synthesise mRNA strand.
2. mRNA then moves out from the nucleus and attaches on the ribosomes on the rough endoplasmic reticulum.
3. Protein is synthesised .and carried to Golgi apparatus in the form of transporting vesicle.
4. The transporting vesicle fuses with the cis end of the Golgi body.
5. In Golgi body, the polypeptide chain is modified into glycoprotein by glycosylation.
6. A secretory vesicle containing amylase enzyme buds off the trans end of Golgi body.
7.The vesicle fuses with the plasma membrane and releases its content outside the pancreatic cell by exocytosis.
Why I differentiate the terms transporting and secretory vesicle?
Transporting vesicle is for transport within the cell itself.
Secretory vesicles is to transport proteins to be released from the cell.
Below is a diagram of what I have explained above.
This essay question integrates a few organelles that you have learnt in the form of a process,it requires you to think more besides only knowing the function of each organelles.