1. Infection and Response
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Infection and Response
AQA 2016 Biology topic 3

2. 3.1 Communicable Diseases
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3. Pathogens
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Pathogens are microbes (micro organisms) that can cause diseases. They can enter the body in a number of ways:
They can be breathed in through the mouth or nose
They can be ingested in water or food
They can enter through cuts or bites in the skin (direct contact)
…or other natural openings…

4. Types of Pathogens
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There are a number of types of pathogens, including:
Bacteria – small living cells that produce toxins and reproduce very quickly
Fungi – they can produce spores and penetrate human skin
A virus – it lives and reproduces quickly inside our cells, causing cell damage
Protists - eukaryotic cells that can spread through vectors

5. Examples of Viral Diseases 1 - HIV
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HIV is spread through sexual contact or exchange of _____ ____ (including blood, a danger for drug users sharing ______). It initially causes flu-like _______. Unless successfully controlled by antiretroviral _____, the virus attacks the body’s ______ system. If enough damage is done the body is at risk to other infections or ______. This late stage HIV is known as _____.
Words – cancer, needles, bodily fluids, drugs, immune, symptoms, cancer

6. Examples of Viral Diseases 2 and 3 – Measles and TMV
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Examples of Viral Diseases 2 and 3 – Measles and TMV
Words – photosynthesise, fever, pathogen, fatal, sneezes, vaccinated
Measles is a viral disease showing symptoms of _____ and a red skin rash. It can be ______ so most children are ______ against it. Measles is spread by inhaling droplets from _____ or coughs.
TMV (tobacco mosaic virus) is a widespread plant ________ that causes a “mosaic” discolouration in the leaf, which affects the plant’s ability to ___________.

7. Examples of Bacterial Diseases
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Salmonella food poisoning is spread through food prepared in _________ conditions. Chickens are vaccinated against salmonella to control its ______. Symptoms of salmonella include fever, _____, vomiting and diarrhoea.
Gonorrhoea is a _______ transmitted disease with symptoms including a thick yellow discharge from the ____ or vagina and pain when _____. It is treated with antibiotics and its spread can be controlled through using ________.
Words – urinating, condoms, unhygienic, cramps, spread, sexually, penis

8. Examples of Fungal and Protist Diseases
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Rose black spot is a ______ disease causing black spots to appear on ______, which then turn yellow and drop early, reducing _________. It is spread through wind and _____ and can be treated using ________ and removing the affected leaves.
Malaria, a ______ disease causing recurring fever and can be _____. The spread of malaria can be limited by limiting the chances of being bitten by a mosquito (the “vector”), such as by stopping them from ______ or sleeping under a ____.
Words – breeding, net, leaves, fungal, protist, photosynthesis, fungicides, rain, fatal

9. Microbes: our defence against them
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Our bodies have defence mechanisms against invading microbes:
The breathing organs have hairs and produce mucus to cover the lining of these organs and trap the pathogens
Hairs and mucus in the nose trap particles that could contain pathogens
The skin acts as a waterproof barrier
The stomach contains hydrochloric acid, which kills bacteria

10. White blood cells
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If microbes enter our body they need to be neutralised or killed. This is done by white blood cells:
White blood cells do 3 things:
They eat the microbe (“phagocytosis”)
They produce antibodies to neutralise the microbe
The produce antitoxins to neutralise the poisons produced by microbes

11. Producing antibodies You’re going down
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You’re going down
Step 1: The white blood cell “sees” the pathogen (microbe)
Step 2: The cell produces antibodies to “fit” the pathogen
Step 3: The antibodies fit onto the pathogens and cause them to “clump”
Step 4: The pathogens are “eaten” by the white blood cells

12. Vaccinations
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Vaccinations work by injecting a small quantity of dead or inactive pathogen into the body. The body is “tricked” into producing antibodies ready for the real thing. The body then “remembers” the microbe by producing memory cells that “remember” it.
No. of cases of TB in Britain
Year
140,000
The spread of diseases can be slowed down using national immunisation programs, such as tuberculosis in 1953:
1953
National vaccination starts

13. Words – viral, immune, diseases, specific, sparingly
Antibiotics
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Antibiotics are used to cure bacterial _______ by killing infective bacteria inside the body. Specific bacteria should be treated with ______ antibiotics.
There are two main issues with using antibiotics:
They don’t do anything to ______ infections
Antibiotics should be used _______ as bacteria can grow _______ to them, e.g. the MRSA “superbug”.
Words – viral, immune, diseases, specific, sparingly

14. Using Painkillers
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Painkillers are drugs used to relieve the symptoms of disease but without killing the pathogens, for example:
Ibuprofen
Paracetamol
Aspirin
Q. What about viral infections?
It is difficult to treat viral infections without damaging the cells the virus has infected.

15. I (accidentally) discovered penicillin in 1928
Alexander Fleming,
Discovering new drugs
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I (accidentally) discovered penicillin in 1928
Penicillin was discovered from the penicillium mould. Most new drugs are synthesised by chemists in the pharmaceutical industry. However, the starting point is often a chemical extracted from a plant. For example:
The heart drug digitalis comes from foxgloves
The painkiller aspirin comes from willow.

16. Researching new medicines
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Before new drugs can be approved they have to go through three stages. What are the advantages and disadvantages of each stage?
1. Is it toxic? Preclinical tests are done on cells
In some of these stages, the drugs are tested for toxicity, efficacy and dose.
2. Is it safe for animals? Animal tests are carried out (still preclinical)
3. Is it safe for humans? Human volunteers are tested on. This happens with low doses at first before finding the optimum dose.

17. Placebos Clinical trials can be done in different ways:
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Clinical trials can be done in different ways:
1) Blind trials
Patients do not know which drugs they are taking – a real drug or a “placebo”
2) Double blind trial
Neither the doctors or the patients know if they are taking the real drug

18. 3.2 Monoclonal antibodies (Biology HT only)
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3.2 Monoclonal antibodies (Biology HT only)

19. Monoclonal Antibodies
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Monoclonal antibodies are basically “identical antibodies” that can be made to bind to a specific cell or chemical. They are the same because they are made from the same parent cell. Here’s how:
Eek!
Step 1: Take an animal (e.g. mouse) and inject it with an antigen
Step 2: Extract the B-lymphocytes that the mouse makes in reaction to the antigen
Step 3: Fuse this lymphocyte with fast- growing tumour cells to make a “hybridoma” (a cell that produces lots of antibodies)
Step 4: The hybridoma then divides really quickly (due to it being made from a tumour cell) which gives you lots of identical antibodies called monoclonal antibodies

20. Uses of Monoclonal Antibodies
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Locating and identifying specific molecules in a cell or tissue by binding them with a fluorescent dye
Testing levels of hormones and other chemicals
What are monoclonal
antibodies used for?
Pregnancy testing
Treating cancer by targeting specific cancerous cells

21. Using monoclonal antibodies to fight cancer
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Radiotherapy and chemotherapy have adverse side effects. Monoclonal antibodies are useful as they specific:
Step 1: Produce monoclonal antibodies that are specific to a cancer cell antigen
Step 2: Inject the antibodies into the blood
There they are!
Step 3: The antibodies bind to the cancer cells and tag them for attack by white blood cells
Step 4: The antibodies can also be attached to a radioactive or toxic substance to deliver it to cancerous cells
I’ll get them!

22. Pros and Cons of Monoclonal Antibodies
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Pros and Cons of Monoclonal Antibodies
Monoclonal
antibodies
Pros
Cons
Cancer treatment
Can still cause side effects such as vomiting, fever and low blood pressure
Target specific cells (unlike radiotherapy, which can kill other cells)
Currently not as widely used as scientists first hoped
Less side effects

23. 3.3 Plant Disease (Biology only)
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24. Plant Diseases (HT only)
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How do you know if a plant is diseased?
1) Stunted growth
2) Spots on leaves
3) Areas of decay
4) Growths
6) Discoloured or malformed leaves
5) Pests
How do you know what to look for?
Reference to a gardening manual or website
Lab tests
Using testing kits that contain monoclonal antibodies

25. Examples of Plant Diseases
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Rose black spot is a ______ disease causing black spots to appear on ______, which then turn yellow and drop early. It is spread through wind and _____ and can be treated using ________ and removing the affected leaves.
TMV (tobacco mosaic virus) is a widespread plant ________ that causes a “mosaic” discolouration in the leaf, which affects the plant’s ability to ___________.
Words – fungal, photosynthesise, virus, leaves, rain, fungicides
Aphids!!!

26. Plant Deficiency Symptoms
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Stunted growth – caused by nitrate deficiency (needed for protein synthesis)
Chlorosis – caused my magnesium deficiency (needed to make chlorophyll)

27. How do plants defend themselves?
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Physical defences
Tough waxy cuticle on leaves and cell walls made of cellulose
Layers of dead cells (i.e. bark) that can fall off
Chemical defences
Plants can use antibacterial chemicals and poisons to warn off unwanted insects:
Back off
Yum
Mechanical adaptations
Thorns or hairs that deter animals
Mimicry or curling their leaves when touched