Endocytosis
Explanation
Unicellular organisms like Amoeba lack specialized organs for nutrition. Instead, they utilize the flexibility of their plasma membrane to ingest food directly from the external environment. This mechanism involves the cell membrane folding inward to engulf particles, a transport process distinct from passive diffusion.
Analysis of Options
- Plasmolysis: Incorrect. Plasmolysis is the process where the protoplasm of a plant cell shrinks away from the cell wall due to the loss of water (exosmosis) when placed in a hypertonic solution. It is not a method of food acquisition.
- Exocytosis: Incorrect. Exocytosis is the process by which a cell transports secretory products or waste materials out of the cell cytoplasm to the exterior environment. It is effectively the reverse of cell eating.
- Endocytosis: Correct. Endocytosis is the cellular process in which substances are brought into the cell. The flexibility of the cell membrane enables the organism to engulf food and other materials from its external environment. In Amoeba, this specific form of endocytosis is often referred to as phagocytosis ("cell eating"), where pseudopodia extend around the food particle to form a food vacuole.
- Osmosis: Incorrect. Osmosis is the movement of solvent molecules (typically water) through a semi-permeable membrane from a region of lower solute concentration to a region of higher solute concentration. It regulates water balance, not the intake of solid food particles.
Key Takeaway
Endocytosis is the process by which Amoeba acquires food, utilizing the flexibility of its cell membrane to engulf particles and form a food vacuole.