Correct Option
The correct option is (b).
Explanation
Endocytosis is a transport process where the cell takes in materials from the outside by engulfing them with its plasma membrane. The flexibility of the membrane is crucial for this mechanism. The opposing process, where materials are expelled, is called Exocytosis.
Statement-wise Analysis
- Statement 1 is Incorrect. The process by which a cell expels undigested waste or secretory products into the external environment is known as Exocytosis (or cell vomiting). Endocytosis strictly refers to the intake of material.
- Statement 2 is Correct. The plasma membrane is not a rigid structure; it is flexible due to its composition of lipids and proteins (as described by the Fluid Mosaic Model). This flexibility allows the membrane to invaginate and pinch off to form vesicles, enabling the process of endocytosis.
- Statement 3 is Correct. Endocytosis enables the cell to engulf food and other materials from the external environment. For example, unicellular organisms like Amoeba acquire their food through this specific process (often referred to as phagocytosis).
Although Statement 3 is factually correct, options (a), (c), and (d) are invalid because they contain the incorrect Statement 1. Therefore, by elimination, option (b) is the selected answer.
Key Takeaway
Endocytosis utilizes the flexibility of the plasma membrane to engulf external materials (intake). Exocytosis is the fusion of internal vesicles with the membrane to release contents (expulsion).