ASBiologyAQARevision NotesCell StructureCell Recognition & the Immune SystemPhagocytosis

Phagocytosis (AQA AS Biology): Revision Note

Exam code: 7401

Alistair Marjot

Written by: Alistair Marjot

Reviewed by: Ruth Brindle

Updated on

Phagocytosis

  • Phagocytes are white blood cells that are produced continuously in the bone marrow

  • There are two main types of phagocyte, each with a specific mode of action:

    • neutrophils

    • macrophages

  • The role of phagocytes is to recognise and engulf pathogens; this process is known as phagocytosis

  • Phagocytosis is an example of a non-specific immune response

The process of phagocytosis

  1. Chemotaxis – Chemicals from pathogens or damaged body cells (e.g. histamines) attract phagocytes to the infection site

  2. Recognition and attachment

    1. Phagocytes detect non-self antigens on pathogens using receptor proteins on their membrane

    2. Receptors bind to antigens on the pathogen’s surface

  3. Engulfment – The phagocyte’s membrane extends around the pathogen, forming a phagocytic vacuole (this is an example of endocytosis)

  4. Phagosome formation – The vacuole containing the pathogen is now called a phagosome

  5. Phagolysosome formation – The phagosome fuses with a lysosome, forming a phagolysosome

  6. Digestion – Lysozymes (digestive enzymes) are released to hydrolyse the pathogen (e.g. breaking down bacterial cell walls)

  7. Antigen presentation – In macrophages, digested pathogen fragments may be displayed on the cell surface to activate the specific immune response

Flowchart of neutrophil phagocytosis showing attraction, attachment, endocytosis, digestion, and antigen presentation with labelled diagrams.
Phagocytosis and antigen presentation

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

    Test yourself
    Previous:AntigensNext:The T Lymphocyte Response
    Author
    Reviewer
    Alistair Marjot

    Author: Alistair Marjot

    Expertise: Environmental Systems and Societies & Biology Content Creator

    Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.

    Ruth Brindle

    Reviewer: Ruth Brindle

    Expertise: Biology Content Creator

    Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. With 10 years of teaching experience across the 3 key science disciplines, Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.