Which process describes cellular eating?

• A. Phagocytosis
• B. Pinocytosis
• C. Diffusion
• D. Osmosis

Answer: (A)

Cellular eating is a form of endocytosis in which the cell surrounds and engulfs solid particles, using its membrane to wrap around the material and pinch off a vesicle called a phagosome. This process is driven by the cytoskeleton and requires energy, making it a way for cells—especially immune cells like macrophages and neutrophils—to ingest bacteria, debris, or other large particles.

Pinocytosis, in contrast, is “cell drinking”—the uptake of extracellular fluid and dissolved solutes in tiny vesicles, not solid particles. Diffusion is the passive movement of molecules down a concentration gradient, without vesicle formation. Osmosis is a specific type of diffusion for water across a membrane. Thus, the process that best describes cellular eating is phagocytosis.