This deep dive covers First Line of Defence: Chemical Barriers within Human Defense Systems - Non-specific for GCSE Biology. Physical and chemical barriers, white blood cell responses, inflammatory response It is section 4 of 16 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
First Line of Defence: Chemical Barriers
Stomach Acid
Your stomach produces hydrochloric acid that creates an extremely hostile environment for pathogens that are swallowed:
- Low pH: Stomach acid has a pH of around 2, killing most bacteria and viruses
- Denatures proteins: The acid destroys the proteins and enzymes that pathogens need to survive
Lysozyme
Lysozyme is an antimicrobial enzyme found in several body secretions:
- Where it is found: In tears, saliva, and mucus
- How it works: It destroys the cell walls of bacteria, killing them
Practice questions for Human Defense Systems - Non-specific
Which part of the body acts as the main physical barrier to prevent pathogens entering?
Explain how mucus and cilia in the airways protect against pathogens.
Quick recall flashcards
What is phagocytosis?
The process by which white blood cells (phagocytes) engulf and digest pathogens or foreign particles.
What is sebum?
An oily substance produced by sebaceous glands in the skin that creates an acidic environment on the skin surface, inhibiting bacterial and fungal growth.