what is pinocytosis

Pinocytosis is a process in cellular biology, also known as fluid endocytosis or cell drinking, where small molecules dissolved in extracellular fluid are taken into the cell through an invagination of the cell membrane, forming small vesicles inside the cell. This process is non-specific and does not require receptor binding. It is used for the absorption of extracellular fluids and small molecules, such as fat droplets, vitamins, and antigens. Pinocytosis involves a considerable investment of cellular energy in the form of ATP and is a type of endocytosis, which is the uptake of substances by a cell. It is different from phagocytosis, which involves the ingestion of large macromolecular structures. The term "pinocytosis" comes from the Greek words "píno," meaning "to drink," and "cytosis," meaning "cell"