That is the vacuole. They usually fill up with food, water, or other various wastes.
Not sure what you mean but here's what i think
1.They are substrate-specific, because it's a lock-and-key mechanism.
2. They are re-used
3. They can catalyze reactions
4. They decrease activation energy
5. They are proteins by nature.
I'm pretty sure the answer is: B. Sickle-cell disease
