White Blood Cells (Cambridge (CIE) IGCSE Biology)

Lymphocytes & Phagocytes: Extended

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