L5 – Treating and preventing disease

Learning ObjectiveTo be able to describe how we treat and prevent disease

Key words: Medicine, Penicillin, antibiotics, immunisation, vaccine

Starter activity: How do we treat disease, what would you use to treat salmonella (bacterial infection)? What would you use to treat the common cold (virus)?

B1 L1

For bacterial Infections - Use Antibiotics

For viruses – Don’t use Antibiotics because they do not work against them so it is left alone for the body to deal with.

Good

Better

Best

Able to explain how we develop antibiotics.

Able to explain how vaccination makes human beings immune to a specific pathogen.

Success Criteria

At the end of this lesson it will be:

Able to state why antibiotics cannot treat viruses

Last lesson linkImmunity

• Once your white blood cells destroy a type of pathogen, you are unlikely to develop the same disease again.

• This is because the white blood cells recognise the pathogen the next time it invades the body and the correct antibodies will kill it very quickly before it can affect you.

• This makes you Immune to the disease and is known as Immunity.

How we get rid of Side effects (Painkillers)

• If you have a sore throat you take a lozenge (medicine) to reduce pain (painkiller).

• However the sore throat is only a side effect of the pathogen and it will not kill the pathogen just take the pain away.

How do we kill Bacteria?

• Antibiotics – These medicines kill bacteria, there are many types used to treat people.– Penicillin was the first antibiotic discovered and works by

breaking down the cell wall of the bacteria causing them to burst.

THEY CANNOT KILL VIRUSES HOWEVER!!

Discovery of Penicillin

1. How was penicillin discovered?2. Why did he know that penicillin killed bacteria?

Why can’t antibiotics kill viruses??

• Antibiotics can’t kill viruses because viruses live and reproduce inside body cells.

• It is very difficult to develop medicine which kills the virus without also destroying the cell

Learning objective check

Good Able to state why antibiotics cannot treat viruses

How are they developed?

• Most antibiotics are developed and tested in sterile petri dishes (contains no other bacteria)

1. Bacteria are placed on small discs of paper containing antibiotics.

2. The discs are placed in a dish containing bacteria growing on a gel.

• The clear zone is where the bacteria have been killed.

• The clear zone is where the bacteria have been killed. Which antibiotic is most effective? Why?

Learning objective check

BetterAble to explain how we develop antibiotics.

How can we combat viruses then?

By Immunisation.We can understand immunisation by learning about small pox and how it was combatted by a man called Edward Jenner.

What is small pox?

• A viral disease similar to chicken pox.• It killed one in three of those who caught it

and badly disfigured those who were lucky enough to survive catching it.

Before Jenner, children were infected with smallpox when they were young in order to give them immunity from it, however many children died as a result.

Edward Jenner

THE COW POX WAS A VERY SIMILAR KEY TO THE SMALL POX AND THEREFORE THE ANTIBODIES MADE BY THE BODY TO KILL THE COWPOX COULD ALSO KILL THE SMALLPOX VIRUS

Lock and Key

What did Jenner do?

• In 1796 he injected a small boy with cowpox.• He used the pus form a blister on a cow!• A few weeks later, he injected him with

smallpox.• The boy survived.

Is it morally right what Jenner did?

Another vaccination method

• Another method of vaccination is to give the person a weakened form of the virus.

• This is exactly what Louis Pasteur did with rabies virus

Lock and Key

Same lock and key just that key is weakened and so does no harm

How do we gain immunity without contracting the disease?

• By Immunisation.• A new-born baby receives antibodies from its

mother in the first few days of feeding.

• When you’re a young child you are immunised to protect you from very harmful diseases, such as polio, measles, mumps and rubella.

The process of vaccination• Immunisation (vaccination) involves:1. Injecting or swallowing a vaccine containing small amount

of dead or weak form of the pathogen.2. As pathogen is weak, no illness but white blood cells still

respond and produce antibodies to destroy the pathogen.

This makes you immune to future infection by that pathogen

Why would you now be immune to that pathogen?

• Your white blood cells will recognise if the pathogen gets into your body and will respond quickly by producing antibodies.

• The pathogen does not get a chance to reproduce enough to make you ill. (i.e. cannot produce enough toxins to make you feel ill)

Learning objective check

BestAble to explain how vaccination make us immune to a specific pathogen.

Exam question

(5)

How can the following drugs be used to treat disease?Painkillers

Antibiotics

Explain how vaccination works:

Why can’t antibiotics be used to kill viruses?

What is a sterile culture in petri dish .

Give 2 reasons it is important to keep cultures sterile. .

How are antibiotics developed and tested? And how can you tell which is most effective?

How do animals gain immunity from bacteria and viruses without contracting them?

What 3 diseases does MMR vaccine protect from?