Final answer:
In phagocytosis, cells that need to be disposed of express phosphatidylserine on the outer membrane as a signal for phagocytosis. During this process, the plasma membrane of the phagocyte extends and forms pseudopodia to surround and ingest the target particle. Clathrin is crucial for stabilizing the membrane during engulfment, and the ingested particle is ultimately digested in a phagolysosome.
Step-by-step explanation:
In phagocytosis, dying cells or cells undergoing apoptosis express phosphatidylserine on the outer face of their cell membrane as a signal for phagocytes, such as macrophages and neutrophils, to engulf them. During phagocytosis, the plasma membrane extends outward and wraps around the target particle by forming structures known as pseudopodia. This membrane encloses the particle in a vesicle known as a phagosome.
The inward-facing part of the plasma membrane that is about to engage in phagocytosis first becomes coated with a protein called clathrin. Clathrin plays a crucial role in stabilizing this section of the membrane. After the engulfment, the vesicle merges with a lysosome, resulting in the creation of a phagolysosome where the ingested particle is digested. Once the nutrients are extracted from the vesicular contents, the remnants are released back into the extracellular fluid, and the membrane is reincorporated into the plasma membrane.
Some pathogens can interfere with this process. For example, the bacterium responsible for anthrax, B. anthracis, secretes enzymes like phospholipase C which can degrade the membrane of the phagosome, preventing the fusion with the lysosome, thereby allowing the pathogen to survive and replicate within the host phagocyte.