Correct Response: A. Phagocytosis is the type of endocytosis that facilitates bringing large particles such as bacteria into the cell. Endocytosis is used when the particles are too large to enter through the plasma membrane. During phagocytosis, the plasma membrane surrounds the particle, enclosing it in a vacuole so that it can be engulfed by the cell. Although a cell is able to deactivate an antigen, such as a pathogen, when it binds to a specific receptor (B) on the membrane, phagocytosis is not necessary for this process to occur. Phagocytosis occurs when particles, including food, are too large to diffuse through the plasma membrane, which is composed of a lipid bilayer (C). Instead the cell surrounds the particle with its membrane and forms a vacuole around the particle to allow digestion. The process of antibody-containing vesicles fusing with the plasma membrane to release the antibodies from the cell (D) is an example of exocytosis, rather than phagocytosis.
