Practice question

Formation of food vacuoles in heterotrophic protists occurs predominantly via phagocytosis, an actin-dependent endocytic process where plasma membrane extends pseudopods enveloping particulate prey such as bacteria or algae, invaginates, and pinches off internally as membrane-bound phagosome. Phagosome subsequently fuses with lysosomes delivering acid hydrolases hydrolyzing macromolecules, nutrients transported into cytoplasm. Residual undigested material undergoes exocytosis. This receptor-mediated process differs from pinocytosis which internalizes fluid phase and diffusion which transports small molecules, providing intracellular digestion capability essential for holozoic nutrition in amoebae and ciliates.