What is the natural skin flora, and how does it reduce the risk of infection?

The natural skin flora is the population of harmless bacteria and yeasts that normally live on the skin, and it protects the body by occupying the available sites and nutrients so that arriving pathogens cannot establish themselves.

How does lysozyme destroy a bacterium?

Lysozyme hydrolyses the bonds within the peptidoglycan of the bacterial wall, so the weakened wall can no longer resist the entry of water and the cell bursts.

What is the role of mucus in the airways?

Mucus is a sticky secretion from goblet cells that traps dust particles and microorganisms in the inhaled air before they can reach the delicate alveoli.

Eduqas A-Level Biology A400QS

Biological Molecules

Topic overview Inorganic ions and the properties of water Monosaccharides and disaccharides Polysaccharides, storage and structure Lipids, triglycerides and phospholipids Amino acids and protein structure Condensation, hydrolysis and the food tests

Cell Structure and Organisation

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Immunology and Disease: The Immune ResponseImmunology

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Human Musculoskeletal Anatomy: Skeletal TissuesMusculoskeletal

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Neurobiology and Behaviour: The BrainNeurobiology

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Immunology and Disease: The Immune Response

Natural barriers to infection

3 things to know
Component 3

Overview

Natural skin flora and role of mucus in the airways.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

How does intact skin act as a barrier to infection?

Key term

Why does the sebum secreted onto the skin surface discourage bacterial growth?

Key term

How do tears protect the surface of the eye from infection?

Questions from this subtopic

Each one with the model answer underneath.

1
How does intact skin act as a barrier to infection?
Model answer
The outer layer is made of dead, flattened cells packed with keratin, forming a dry, tough and continuous covering that most microorganisms cannot penetrate or grow on.
2
What is the natural skin flora, and how does it reduce the risk of infection?
Model answer
The natural skin flora is the population of harmless bacteria and yeasts that normally live on the skin, and it protects the body by occupying the available sites and nutrients so that arriving pathogens cannot establish themselves.
3
Why does the sebum secreted onto the skin surface discourage bacterial growth?
Model answer
Sebum contains fatty acids that lower the pH of the skin surface, and most pathogenic bacteria cannot grow well in acidic conditions.
4
How do tears protect the surface of the eye from infection?
Model answer
Tears wash particles and microorganisms off the exposed surface, and they contain the enzyme lysozyme, which destroys bacteria caught in them.
5
How does lysozyme destroy a bacterium?
Model answer
Lysozyme hydrolyses the bonds within the peptidoglycan of the bacterial wall, so the weakened wall can no longer resist the entry of water and the cell bursts.
6
What is the role of mucus in the airways?
Model answer
Mucus is a sticky secretion from goblet cells that traps dust particles and microorganisms in the inhaled air before they can reach the delicate alveoli.

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