White Blood Cells: Extended (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

Extended Tier Only

• White blood cells are part of the body’s immune system, defending against infection by pathogenic microorganisms
• There are two main types, phagocytes and lymphocytes

Phagocytes

• Carry out phagocytosis by engulfing and digesting pathogens

Phagocytosis

• Phagocytes have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
• Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it
• They can be easily recognised under the microscope by their multi-lobed nucleus and their granular cytoplasm

Lymphocytes

• Produce antibodies to destroy pathogenic cells and antitoxins to neutralise toxins released by pathogens
• They can easily be recognised under the microscope by their large round nucleus which takes up nearly the whole cell and their clear, non-granular cytoplasm

Lymphocytes and phagocytes can be identified on a micrograph image