The Cell Anatomy and Physiology Practice Test

Endocytosis covers several different ways cells bring material inside by wrapping the membrane around it to form a vesicle. Each method handles different cargos and has a distinct mechanism, but they all share the same idea of taking material in through the plasma membrane.

Pinocytosis is the non-specific uptake of extracellular fluid and dissolved solutes. It happens relatively routinely and doesn’t require matching a ligand to a receptor, so it’s like cell drinking.

Phagocytosis is the uptake of large particles, such as bacteria or dead cells, by specialized cells (like macrophages and neutrophils). It involves extensive membrane remodeling and cytoskeletal changes to engulf the particle, forming a phagosome that later fuses with a lysosome for digestion.

Receptor-mediated endocytosis is a highly specific process. Ligands bind to particular receptors on the cell surface, and the receptor–ligand complexes are internalized, often via clathrin-coated pits. This pathway concentrates and imports particular substances, such as cholesterol via LDL receptors or iron via transferrin receptors.

Because all three are forms of endocytosis, the best answer is that all of the above are endocytosis types.