Within a eukaryotic cell, which one of the following organelles mainly functions as a storehouse of digestive enzymes responsible for intracellular digestion?

Introduction / Context:
Although this question appears under chemistry, it actually touches on cell biology, which is often included in general science sections of competitive exams. The question asks which cell organelle functions as a storehouse of digestive enzymes and is responsible for intracellular digestion. Understanding the roles of lysosomes, ribosomes, desmosomes and vacuoles is essential in basic biology and helps build a picture of how cells maintain and recycle their own components.

Given Data / Assumptions:
Desmosomes are specialised structures involved in cell adhesion, particularly in epithelial tissues.
Ribosomes are small ribonucleoprotein particles involved in protein synthesis in the cytoplasm or on the rough endoplasmic reticulum.
Lysosomes are membrane bound vesicles that contain a variety of hydrolytic enzymes active at acidic pH.
Vacuoles are membrane bound compartments mainly involved in storage and turgor maintenance, especially in plant cells.
We assume a standard eukaryotic cell with these organelles present and performing their textbook functions.

Concept / Approach:
The key concept is that lysosomes are often described as the digestive system or waste disposal system of the cell. They contain hydrolytic enzymes capable of breaking down proteins, nucleic acids, lipids and carbohydrates. These enzymes function best at acidic pH, which is maintained inside the lysosome. When cellular components are damaged or obsolete, or when foreign materials are taken up by endocytosis or phagocytosis, lysosomes fuse with the vesicles containing the material and digest it. None of the other organelles listed act as a general storehouse for digestive enzymes in the cytoplasm.

Step-by-Step Solution:
Step 1: Consider desmosomes. They are intercellular junctions that provide mechanical strength by holding adjacent cells together, especially in tissues subject to stress. They do not contain digestive enzymes for intracellular digestion. Step 2: Consider ribosomes. Ribosomes are the sites of protein synthesis, where messenger RNA is translated into polypeptide chains. They are not storage sites for digestive enzymes. Step 3: Consider lysosomes. Lysosomes are membrane bound organelles that house many hydrolytic enzymes capable of digesting a variety of biomolecules. They are directly responsible for intracellular digestion and recycling of cellular components. Step 4: Consider vacuoles. Vacuoles in plant cells store water, ions and sometimes pigments or waste products. In animal cells, small vacuoles may be involved in storage or transport but are not the main library of hydrolytic enzymes. Step 5: From this comparison, lysosomes clearly fit the description of an organelle that acts as a storehouse of digestive enzymes responsible for intracellular digestion.

Verification / Alternative check:
Standard biology textbooks describe lysosomes as the suicidal bags or digestive bags of the cell because they contain powerful enzymes that can digest cellular components when released. Experimental evidence shows that if lysosomal membranes are damaged, the enzymes can digest parts of the cell. In contrast, desmosomes are visible under the microscope as thickened regions of the plasma membrane between cells, ribosomes are visible as small granules involved in protein synthesis, and vacuoles are large storage compartments especially in plant cells. These observations reinforce that only lysosomes match the functional description given in the question.

Why Other Options Are Wrong:
Desmosomes are wrong because they serve as anchoring junctions between cells and do not store or release digestive enzymes.
Ribosomes are wrong because they are involved in protein synthesis, not in digestion of biomolecules, and they do not act as enzyme storage vesicles.
Vacuoles are wrong because their primary role is storage of substances like water or ions and maintaining turgor pressure, rather than housing a full complement of hydrolytic enzymes for intracellular digestion.

Common Pitfalls:
Students may confuse vacuoles and lysosomes because both are membrane bound vesicles. In some animal cells, lysosomal functions and vacuolar functions can overlap, but the classical distinction in basic biology is that lysosomes are specifically enriched with digestive enzymes. Another pitfall is to assume that any organelle involved in protein processing must hold digestive enzymes, whereas only lysosomes are specialised for degradation. Keeping clear mental pictures of the functions of each organelle helps avoid such mistakes in multiple choice questions.

Final Answer:
The cell organelle that mainly functions as a storehouse of digestive enzymes is the Lysosome.