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Copy of Pathogens, Disease and Defenses

GCSE Science A B1 1.3-1.4

Bo Breese

on 27 September 2017

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Transcript of Copy of Pathogens, Disease and Defenses

Pathogens, Disease and Defences
What are pathogens?

How do pathogens cause disease?

Why was the work of Ignaz Semmelweis important?

How does your body stop pathogens getting in?

How do white blood cells protect us from disease?
Learning Objectives
What diseases have you or your family had?

What caused the disease?

How severe was the disease?
Disease that can spread from person to person

Mild - Common Cold or Tonsillitis

Severe - Tetanus, Influenza and HIV

Caused by pathogen
Infectious Disease
Microorganism - bacteria, virus or other organism that can only be seen using a microscope.

Pathogen - Microorganism that cause disease

Key Terms
Single cellular organism

Smaller than animal or plant cells.

Some are harmful - E.Coli and S.Aureus

Many are harmless.
Staphylococcus Aureus can cause MRSA
Salmonella is associated with food poisoning
Even smaller than bacteria!

Usually very regular shapes

Can infect every type of living organism (even bacteria!)
Bacteriophage are able to infect bacterial cells
Retrovirus like the one above are known to cause HIV
Once inside the body, bacteria and viruses reproduce rapidly.

They will harm you in different ways...
How do they cause disease?
Bacteria reproduce rapidly (simply splitting in two)...

This may cause physical damage to your cells and tissues

Bacteria also produce toxins that affect your body.

Viruses insert DNA into nucleus and take over control of your cells.

The cell then produces millions of new viral particles

Infected cells fill up with viruses and then rupture, spreading the virus.

Viruses rarely produce toxins.
Symptoms are a result of the damage and toxins caused by the pathogens.

Many symptoms are also a result of the bodies response to the disease.
Ignaz Semmelweis
Pathogens must spread in order to infect other people.

How might pathogens spread?
Spreading Disease
1. Droplet infection

2. Direct contact - including
Sexually Transmitted Diseases (STDs).

3. Contaminated food and drink into gut and blood stream.

4. Cuts, scratches and needle punctures allow direct route into the bloodstream.
Draw the diagram below and describe how the body is able to prevent the entry of pathogens into the body...
Then watch the video on how viruses invade the body.
How do viruses enter the body?
Blood clots and scabs
If pathogens make it past your first line of defence your body has a group of highly specialised cells to call on!
Second line of defense...
White Blood Cells!
Some white blood cells (Phagocytes) ingest pathogens to destroy them.
Some white blood cells produce chemicals called antibodies that target
specific bacteria and virus.

Some white blood cells can also remember pathogens and will be able to kill them much quicker if they reinvade - this is immunity.
Other white blood cells produce antitoxins that counteract the toxins released by bacterium.
Pathogens (bacteria and viruses) cause infectious disease.

Pathogens rapidly reproduce inside your body increasing infection.

Bacteria release harmful toxins that make you ill.

Ignaz Semmelweis recognized the importance of hand washing to reduce spread of infection.

The body has a first line of defense against infection (skin, mucus and blood clotting)

It also has a second line of defense. Specialized white blood cells that can ingest or release antibodies to kill pathogens or produce antitoxins to reduce negative effects.
Read the article on Germ Defense.

Using the article complete the crossword puzzle. (Homework if not finished in class.)
Ignaz Semmelweis
Semmelweis recognised the importance of handwashing in preventing the spread of infectious disease...
Full transcript