Glossary
phagocytosis
Phagocytosis is a cell taking in a solid particle by wrapping its membrane around it, then digesting it in a vesicle.
Phagocytosis is a cell taking in a solid particle by reaching around it. The membrane pushes out extensions, closes over the particle, and pinches off a vesicle inside the cell — the particle is now enclosed in membrane that used to be the surface. A lysosome then fuses with that vesicle, its enzymes break the contents down, and whatever is useful is absorbed. The cells that do it most are the white blood cells that clear bacteria and debris, which is why the word turns up in any account of an infection. Two distinctions get tested. Taking in fluid rather than a particle is pinocytosis, and taking in a specific molecule through a receptor is receptor-mediated endocytosis. And the direction matters: phagocytosis brings material in, while exocytosis sends it out.
Taught in
Related terms
- exocytosis — Exocytosis is a vesicle fusing with the cell membrane and releasing its contents outside the cell — how a cell secretes what it makes.
- antibody — An antibody is a protein made by plasma cells, derived from activated B cells, that binds one specific antigen and marks it for destruction.
Source: The biology guide in this course: its genetics definitions follow the National Human Genome Research Institute's Talking Glossary of Genomic and Genetic Terms, and its process descriptions follow the US National Cancer Institute's SEER Training Modules. Both are US federal government material, not subject to copyright in the United States. The microbiology entries — the bacterial cell, the Gram stain and the chain of infection — were written for this course from the infection-control guidance the biology guide's own source list names (US Centers for Disease Control and Prevention), which the genetics glossary does not cover. The definitions above are written for this course in our own words. (NHGRI Talking Glossary accessed 2026-10-26; definitions written 2026-10-27; the CDC basis for the microbiology entries — Principles of Epidemiology in Public Health Practice, third edition — accessed 2026-10-28, the date the biology guide's own source list records)