An amoeba continuously forms small vesicles at its membrane, each capturing an undifferentiated sip of dissolved solutes from the surrounding water rather than any targeted molecule. Which process is occurring?

Core Concept

Pinocytosis invaginates tiny droplets of extracellular fluid without selecting individual cargo, letting the cell sample dissolved nutrients broadly. Each vesicle carries whatever happened to be dissolved in the swallowed volume. This contrasts with receptor mediated uptake, which concentrates one specific ligand before the membrane closes.