Final answer:
The organelle where intracellular digestion occurs is the lysosome, which contains digestive enzymes to break down various substances and is key in cellular processes like autophagy and immune responses.
Step-by-step explanation:
The organelle responsible for intracellular digestion is the lysosome. Lysosomes are small, spherical compartments part of the endomembrane system. They contain digestive enzymes and are involved in the process of breaking down various substances such as food particles, damaged organelles, cellular debris, and even microorganisms. This function is sometimes referred to as "cellular garbage disposal". Lysosomes maintain a more acidic pH suited for the function of these enzymes, compared to the cytoplasm.
Furthermore, lysosomes play a key role in autophagy, the process where a cell digests its own damaged structures, and in immunity, where white blood cells use lysosomes to break down ingested foreign materials. The enzymes that reside in lysosomes are synthesized in the Rough Endoplasmic Reticulum and then transported to the Golgi apparatus, where they are modified and packaged into vesicles that may fuse with existing lysosomes or form new ones.