1. Which organelle is called 'digestive bag' and why?

Lysosomes are called the 'digestive bags' of the cell because they contain powerful hydrolytic enzymes capable of breaking down all types of biological macromolecules including proteins, carbohydrates, lipids, and nucleic acids. These membrane-bound organelles function as the cell's waste disposal system, digesting unwanted materials, worn-out organelles, and foreign particles that enter the cell through phagocytosis. The enzymes work optimally in acidic conditions (pH 4.5-5.0), which is maintained within the lysosomal membrane.

The term 'digestive bag' is particularly fitting because lysosomes literally digest cellular debris and recycle the resulting building blocks for reuse by the cell. When a cell component becomes damaged or old, it gets enclosed in a membrane and fuses with a lysosome, where enzymatic digestion occurs. This process, called autophagy, is essential for cellular maintenance and survival. In white blood cells, lysosomes play a critical defense role by digesting bacteria and viruses, demonstrating their protective function beyond routine cellular housekeeping.