Penicillin is produced in a fermenter by growing the fungus Penicillium. The graph shows how the mass of living Penicillium fungus and the concentration of penicillin change over time.
When is the best time to collect the penicillin?
A) at 1.5 days
B) at 3.0 days
C) at 3.5 days
D) at 5.0 days
▶️ Answer/Explanation
Ans: D
Penicillin is a secondary metabolite, meaning it is produced after the Penicillium fungus reaches the stationary phase of growth (when growth slows). The graph shows that penicillin concentration peaks at 5.0 days, while the fungal mass stabilizes. Earlier time points (A–C) represent active growth phases with lower penicillin yields. Thus, the optimal harvest time is D (5.0 days).
The diagram shows some apparatus that was used to produce lactose-free milk.
The alginate beads do not react with any of the substances. X is an enzyme that catalyses a reaction involving one of the substances found in milk.
What are X and Y?
| X | Y | |
|---|---|---|
| A | amylase | glucose |
| B | amylase | starch |
| C | lactase | glucose |
| D | lactase | starch |
▶️ Answer/Explanation
Ans: C
To make lactose-free milk, lactase (X) breaks down lactose into glucose and galactose (Y would include glucose). Amylase (A/B) breaks down starch, which isn’t relevant here. The correct pair is C: lactase and glucose, as lactose is milk’s sugar.