Protein processing: rER and GolgiEdexcel A-Level Biology A: Mind map

Exam questions on Protein processing: rER and Golgi

1. Acinar cells of the pancreas make and secrete large quantities of the digestive enzyme amylase into the pancreatic duct. Electron micrographs of these cells show extensive rough endoplasmic reticulum, a prominent Golgi apparatus and many vesicles close to the cell-surface membrane.
   Explain why these cells have extensive rough endoplasmic reticulum.2 marks
2. Pancreatic cells were incubated for three minutes in a medium containing radioactively labelled amino acids and then transferred to a medium containing only unlabelled amino acids. Samples were taken at intervals and the position of the radioactivity in the cells was found. After 5 minutes most of the radioactivity was in the rough endoplasmic reticulum, after 20 minutes it was mostly in the Golgi apparatus, and after 60 minutes it was in vesicles near the cell-surface membrane and in the surrounding medium.
   Explain why radioactivity was found first in the rough endoplasmic reticulum.2 marks
3. A researcher treats pancreatic cells with a toxin that prevents vesicles from the rough endoplasmic reticulum from fusing with the Golgi apparatus. The untreated cells normally secrete digestive enzymes.
   Predict and explain the effect of the toxin on the position of enzyme proteins in the cell and on the secretion of enzymes.3 marks