Essential Idea:
The human body has structures and processes that
resist the continuous threat of invasion by pathogens
Understandings:
- The skin and mucous membranes form a primary defence against pathogens that cause infectious disease
- Cuts in the skin are sealed by blood clotting
- Clotting factors are released from platelets
- The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin
- Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to disease
- Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity
- Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic cells
- Viruses lack a metabolism and cannot therefore be treated with antibiotics
- Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance
Applications:
- Causes and consequences of blood clot formation in coronary arteries
- Florey and Chain’s experiments to test penicillin on bacterial infections in mice
- Effects of HIV on the immune system and methods of transmission