Final answer:
The complement system in biology performs functions such as enhancing engulfment of pathogens, opening pores in microbial cell membranes to destroy pathogens, and labeling pathogens for phagocytosis.
Step-by-step explanation:
The complement system in biology serves several functions. Firstly, complement proteins act as markers to indicate the presence of a pathogen to phagocytic cells like macrophages and B cells, enhancing engulfment through a process called opsonization. Secondly, certain complement proteins can combine to form attack complexes that open pores in microbial cell membranes, leading to the destruction of pathogens by causing their contents to leak. Lastly, complement proteins can bind to the cell membrane of the pathogen and label it for phagocytosis, also known as opsonization.