Organelles and Compartmentalization · Paper 2 — Free Biology SL Practice Questions

A group of students investigated the effect of a drug on protein secretion from pancreatic acinar cells. They measured the concentration of a digestive enzyme in the extracellular medium over $30$ minutes under two conditions: normal cells and cells treated with a drug that disrupts the Golgi apparatus. All cells were maintained at $37°\text{C}$ in an isotonic buffer. Condition — Enzyme concentration at $t = 0\,\text{min}$ — Enzyme concentration at $t = 30\,\text{min}$ Normal cells — $0.0\,\text{mg mL}^{-1}$ — $2.4\,\text{mg mL}^{-1}$ Golgi-disrupted cells — $0.0\,\text{mg mL}^{-1}$ — $0.3\,\text{mg mL}^{-1}$

A researcher studies a eukaryotic cell genetically modified so that its lysosomal membrane is permeable to protons ($\text{H}^+$ ions). The cell is placed in culture medium at $\text{pH}\ 7.2$.

Hepatocytes (liver cells) are highly active in endocytosis and phagocytosis, internalising materials into phagosomes that fuse with lysosomes for digestion. A research team investigates the effect of a novel drug, EndoX, on lysosomal function in hepatocytes. They measure the activity of the lysosomal hydrolase Cathepsin D and the intralysosomal pH under two conditions. Condition — Cathepsin D activity / AU — Intralysosomal pH A — untreated — 85 — 4.8 B — EndoX-treated — 22 — 6.9 - Optimum pH for Cathepsin D (determined in vitro): $4.5$ to $5.0$ - Cytosolic pH of hepatocytes: $7.2$