Biology Disease and Immunity

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What is a pathogen?
A pathogen is an organism which causes disease
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What are 3 pathogenic microorganisms?
Fungi, bacteria and viruses
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How do pathogens enter the body?
Skin - through open wounds, digestive system - through food and drink we consume and gas exchange system - most will be trapped in mucus lining
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How do pathogens cause disease?
Production of toxins and call damage - rupturing, the breaking down of nutrient in cell and replication
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What are some lifestyle factors that increase your risk of CHD?
Poor diet - high in sat fat / salt, smoking, lack of excersize and alcohol intake
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What is cancer and what are the factors that increase your risk of developing it?
Cancer is the result of uncontrolled cell division. Risk factors are: smoking, excessive exposure to light and excessive alcohol intake
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What are antigens?
Antigens are a forgein substance which induces an immune response in the body, especially in the production of antibodies
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What is a phagocyte?
It's a type of white blood cell which carries out phagocytosis, which is the engulfment of pathogens. They are found in the blood and tissues
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Phagocytosis is called the 'immune response' and has 5 stages, describe these stages...
1 Phagocyte recognises antigens on pathogen 2 engulfs pathogen 3 pathogen in phagocytic vacuole in the cytoplasm 4 a lysosome fjses with vacuole and lysosomal enzymes break down pathogen 5 sticks antigens on surface, activates immune system cells
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What are T Cells? (Natural killer cells)
Another type of white blood cell, proteins on surface bind to antigens - activates it. Some release substances to active B cells, others attach to antigens and kill cell. Mature in thymus
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What are B Cells?
Formed in the bone marrow. Covered with antibodies - protiens that bind antigens to forn a complex. Different shaped antibody on membrane, different ones bind to different shaped antigens. B cells divide into plasma cells when activated
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What are plasma cells?
Identical to B cells. They secrete lots of antibody specific to antigen. They coat pathogen - easier to engulf, prevents fro entering host cells and binding to & neutralising toxins produced by pathogen
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What immune responses are B cells and T cells?
B cells = humoral response and T cells = cellular response
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What is the Primary response?
When an antibody enters the body for the first time it actives the immune system
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Why is the Primary response slow?
Because there aren't many B cells that can make the antibody needed to bind to it. Eventually the body will produce enough of the right antibody to overcome infection
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After being exposed to an antigen, what do T cells and B cells produce?
Memory cells which remain in the body for a long time. Memory T cells remember antigen and B cells record the antibodies needed to bind the antigen. The person is now immune and will respond quickly 2nd time
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What is the Secondary response?
If the same antigen enters body again, immune system will produce a quicker, stronger immune response. Often gets rid of pathogen before you start to show any symptoms
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What do memory B cells do in the Secondary response?
They divide into plasma cells that produce the right antibody to the antigen
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Wwhat do memory T cells do in the Secondary response?
They divide into the correct type of T cells to kill the cell carrying the antigen
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What to vaccines contain?
Antigens that cause your body to produce memory cells
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What is herd immunity?
As they reduce the occurance of the disease, those who aren't vaccinated are less likely to catch disease; there are fewer people to catch it from
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How can vaccines be taken?
They may be injected or taken orally
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What is a disadvantage of taking a vaccine orally?
It could be broken down by enzymes in the gut or the molecules may be too large to be absorbed into the blood
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Why are booster vaccines given sometimes?
To make sure the memory cells are produced
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What do antigens on the surface of pathogens do?
They activate the primary response
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What is antigenic variation?
It's where some pathogens change their surface antigens
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Why is antigenic variation bad?
Because memory cells produced from the first infection will not recognise the different antigens, therefore a new primary response has to be carried out. Meaning vaccines are difficult to develop
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What are monoclonal antibodies?
They are antibodies, produced from a single group of genetically identical B Cells
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Why are antibodies specific?
Because their binding sites have a unique structure that only 1 antigen will fit into
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What does the MMR vaccine protect you against?
Measles, mumps and rubella
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What are some ethical issues on vaccines and antibodies?
Testing on animals, testing on humans can be tricky, some don't want to take the vaccine; of risk of side effects and if there was an epidemic of a new disease there would be a rush to recievethe vaccine
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Card 2


What are 3 pathogenic microorganisms?


Fungi, bacteria and viruses

Card 3


How do pathogens enter the body?


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Card 4


How do pathogens cause disease?


Preview of the front of card 4

Card 5


What are some lifestyle factors that increase your risk of CHD?


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