Which form of endocytosis involves the uptake of small particles, often liquids, into the cell?

• A. Endocytosis
• B. Phagocytosis
• C. Pinocytosis
• D. Exocytosis

Answer: (C)

Pinocytosis is a form of endocytosis in which the cell takes in extracellular fluid and dissolved solutes by forming small vesicles from the plasma membrane. This is often described as cellular drinking, because the cargo is liquids or very small particles rather than large solids. The vesicles are small and carry solutes, fitting the description given. In contrast, phagocytosis handles large particles like bacteria or debris by wrapping them with membrane extensions called pseudopods. Exocytosis is the process of exporting substances from the cell, not taking them in. Endocytosis is the broader category that includes pinocytosis and phagocytosis. So the uptake of small particles, often liquids, is pinocytosis.