Phagocytosis is best described as which of the following?

• A. Cell eating
• B. Cell drinking
• C. Receptor-mediated uptake
• D. Passive diffusion

Answer: (A)

The main idea is that phagocytosis is the process by which a cell ingestes large, solid particles by wrapping its membrane around them—driven by actin rearrangements—to form a phagosome. This is what people mean by “cell eating.” It’s a distinct mode of uptake from other forms of endocytosis that handle fluids or small molecules. For example, taking up extracellular fluid and dissolved solutes is cell drinking (pinocytosis), not solid particle engulfment. Passive diffusion is simply the movement of tiny molecules across the membrane without vesicle formation or energy-driven remodeling. While receptors (such as opsonin receptors) can play a role in triggering phagocytosis, the defining description centers on engulfing solid particles, i.e., eating.