The correct answer is option 3: Lysosome. Lysosomes are cell organelles that primarily function as the storehouse of digestive enzymes. They contain a variety of hydrolytic enzymes that are responsible for breaking down various substances, such as proteins, carbohydrates, lipids, and nucleic acids, into simpler molecules that can be recycled or eliminated by the cell. The enzymes present in lysosomes work best under acidic conditions, which is maintained by the lysosomal membrane. The acidic environment is crucial for the proper function of the enzymes and to prevent damage to the rest of the cell.

Option 1: Desmosome is a cell junction structure that plays a role in cell adhesion, but it is not involved in storing digestive enzymes.

Option 2: Ribosomes are responsible for protein synthesis and are not involved in storing digestive enzymes.

Option 4: Vacuoles are membrane-bound organelles involved in various functions such as storage, digestion, and maintaining cell turgor, but they do not primarily function as the storehouse of digestive enzymes like lysosomes do.