Final answer:
The pathway from the PM to a lysosome commences with phagocytosis, where a pathogen is engulfed and enclosed in a phagosome. The phagosome fuses with a lysosome to create a phagolysosome, where the pathogen is digested. This process is integral to the body's immune response and the endomembrane system.
Step-by-step explanation:
The pathway from the PM to a lysosome involves a sequence of events where a pathogen is first engulfed by a phagocyte through phagocytosis. This engulfed pathogen becomes enclosed within a vesicle known as a phagosome.
Lysosomes, which contain digestive enzymes, then fuse with the phagosome to form a phagolysosome, where the pathogen is digested and broken down. Finally, the soluble debris from the degraded pathogen is expelled from the cell through exocytosis.
During endocytosis, a portion of the plasma membrane coated with the protein clathrin invaginates, engulfing the pathogen, which then separates from the plasma membrane to form a vesicle. This vesicle loses its protein coat and fuses with an early endosome, eventually becoming a lysosome after enzymatic digestion.
Lysosomes are an essential part of the endomembrane system and play a significant role in the immune system by using hydrolytic enzymes to destroy any disease-causing organisms that enter the cell.