Phagocytosis is when a white blood cell - or "phagocyte" - engulfs a pathogen that has entered the body and has made it past the body's physical barrier defences.The phagocyte first locates the pathogen (as the pathogen naturally releases chemicals that the phagocyte can detect.) Then the phagocyte binds the pathogen, engulfs it and breaks it down, killing the pathogen.(This would typically be a 4-5 mark question)