Final answer:
The complement system is a series of proteins that work in a cascade to enhance immune responses, mark pathogens for destruction, and directly lyse invading microbes.
Step-by-step explanation:
The complement system is a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. It is made up of a group of proteins that work in a cascading fashion, where the binding of one protein leads to the activation of the next protein in the sequence.
This sequence results in functions including opsonization, which marks pathogens for phagocytosis, and the formation of membrane attack complexes that lyse the pathogens by creating pores in their membranes.