5.2 phagocytosis

Question 1

When does phagocytosis occur?

Answer 1

If a pathogen surpasses the physical or chemical barrier (the first defence).

Question 2

Describe the process of phagocytosis.

Answer 2

• chemical products of pathogens or dead/ inactive cells act as an attractant, causing phagocytes to move towards them
• phagocytes have receptors on their cell-surface membrane which recognise and attach to chemicals on the surface of a pathogen,
• they engulf the pathogen to form a a vesicle (phagosome)
• lysosomes move to vesicle and fuse with it
• lysozymes destroy ingested bacteria by hydrolysis of their cell wall .
• soluble products of the breakdown are absorbed into the cytoplasm of the phagocyte