Functional System of the Cell
Ingestion by the Cell - Endocytosis The cell obtains its nutrients and other substances from the surrounding fluid through Diffusion and active transport. Active transport consists of endocytosis, the principle forms are pinocytosis and phagocytosis. Pinocytosis means the ingestion of small globules of extracellular fluid forming minute vesicles in the cell cytoplasm. The molecules attach to receptors on the membranes, call coated pits, and on the inside of this cell membrane beneath these pits is latticework of fibrillar protien called clathrin and a contractile filament of actin and myosin. After the protein molecules bind with the receptors, the membrane invaginates, and the contractile protiens surround the pit, causing the boarders to close over the attached proteins and form a pinocytotic vesicle. Phagocytosis is the ingestion of large particles like bacteria, cells, and portions of degenerated tissue. Macrophages and some white cells perform phagocytosis. ...