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46 Cards in this Set
- Front
- Back
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Phagocytosis is carried out by... |
white blood cells |
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What is produced in phagocytosis? |
Phagocyte such as a macrophage |
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Describe the process of phagocytosis. |
1) The pathogen is detected, and the phagocyte is attracted to it by the chemicals released 2) The pathogen is engulfed by the macrophage 3) The pathogen enters the cytoplasm in a vesicle 4) Lysosomes fuse with the vesicle releasing lysozyme 5) The lysozyme hydrolyses the pathogen |
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What happens to the pathogen after its hydrolysed in phagocytosis? |
1) Waste materials are ejected from the cell 2) An antigen presenting cell is produced |
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How is an antigen presenting cell useful? |
T-cells can not respond to antigens directly. An APC will process and present the antigen to the T-cells |
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What is specific immunity? |
A specific response to a specific antigen on the surface of a cell or pathogen that has been recognised as a non-self |
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Give the definition of an antigen. |
An antigen is a molecule, usually a protein that stimulates an immune response resulting in the production of specific antibodies |
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Why do our own body cells have antigens? |
To identify each cell and to ensure they are not destroyed in an immune response |
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Give the definition of an antibody. |
A protein/glycoprotein made in response to foreign antigens- has binding sites which bind specifically to antigen. They are produced by B cells |
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Describe the structure of an antibody. |
- complex quaternary structutre - four polypeptide chains - Y shaped - main part is the heavy chain - the light chain can be changes and is the binding site |
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Why can antibodies only bind to specific antigens? |
The binding is specific to certain antigens, form an antigen-antibody complex |
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How do antibodies destroy pathogens? |
They cause agglutination and allow phagocytes to digest many pathogens at the same time |
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What happens during a humoral response, with antibodies? |
The B cells that clone into plasma cells to produce antibodies specifically bind to the invading pathogens antigens |
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What happens during cellular response? |
1) Phagocyte engulfs the pathogen, hydrolyses it, presents the antigens on its surface 2) T cell with specific antigen receptor binds to presented antigen 3) Once binded, the T cell is activated and divides by mitosis creaing clones to help fight the infection |
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What happens during clonal selection? |
1) A specific T cell binds to presented antigen 2) T cell is activated and clones to produce many T cells with complimentary receptors |
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List the two roles of a T cell. |
1) T Cytotoxic cells 2) T helper cells |
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What does a T cytotoxic cell do? |
Locates and destroys pathogens. They release perforin which puts holes in the cell membrane. Or release nitric oxide which is toxic to pathogens |
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What is the role of T helper cells? |
1) Release chemicals that attract phagocytes and B cells 2) Activate B cells 3) Stimulate T cytotoxic cells |
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How are B cells activated? |
1) A T cell binds to the complimentary antigen presented and activate a B cells 2) T helper cells release chemicals that signal the B cell clone |
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What do B cells produce? |
1) Plasma cells 2) Memory cells |
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What are plasma cells? |
Produce specific antibodies |
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What are memory cells? |
Remain in the body to respond to the pathogen quicker if are-infection occurs |
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How do antibodies destroy bacteria? |
1) Antibodies bind to the bacteria surface 2) Damage the bacterial cell membrane 3) Bacterial cell lyses leading to its destruction |
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How do memory cells help to destroy pathogens? |
1) Memory cells encounter specific antigen 2) Memory cells are activated and divide rapidly 3) Memory cells clone into plasma cells and more memory cells 4) Plasma cells produce specific antibodies without the time consuming primary response |
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What is the secondary response? |
When memory cells are activated to produce antibodies |
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Why is a secondary response usually effective? |
Most pathogens have the same antigens on their surface and are recognised by the memory cells |
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What is antigenic variability? |
A change in the antigen which makes it more difficult to develop vaccines |
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How does antigenic variability occur? |
Some pathogens have antigens that mutate and change shape meaning memory cells can not detect them and a secondary response is not initiated. |
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What is a mono-clonal antibody? |
An antibody that is only specific to one antigen |
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What is a vaccine? |
An injection of antigens from a dead or attenuated pathogen that stimulate an the production of antibodies. |
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What is the effect of a vaccine? |
You are immune to the pathogen without getting any symptoms |
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What is herd immunity? |
Vaccines protect those that have had them and reduce the occurrence of the disease, protecting those who are not vaccinated |
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What are the disadvantages of taking a vaccine orally? |
1) The vaccine could be broken down by enzymes in the gut 2) The molecules of the vaccine may be too large to be absorbed into the gut |
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Why are booster vaccines given? |
To ensure there are memory cells |
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What is passive immunity? |
Antibodies are not produced by the individual, eg. given by the mother or an antiserum |
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Why is passive immunity short term? |
- no contact with the pathogen - no memory cells are produced - however it takes effect immediately - antibodies are broken down |
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What is active immunity? |
Immunity provided by the memory cells that are produced after a primary immune response |
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Why is active immunity long term? |
- exposed to the pathogen - takes time to work - memory cells are produced |
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What are the ethical issues associated with vaccines? |
1) testing involves the use of animals 2) human testing 3) who can afford it? 4) side-effects |
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What are the benefits of monoclonal antibodies? |
Monoclonal antibodies can to made to bind to a specific antigen or molecule |
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Describe how monoclonal antibodies are used to treat cancer. |
1) Monoclonal antibody is made to bind to tumour markers 2) Anti-cancer drugs are attached to the antibody 3) The antibody binds only to the tumour markers 4) The drug will only accumulate where there are cancer cells |
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Describe how monoclonal antibodies are used for pregnancy tests. |
1) The antibodies for hCG are bound to a coloured bead 2) Urine is applied and the hCG will bind to the antibody 3) The urine moves up the stick to the test strip where there are immobolised antibodies to hCG which attach to the beads 4) The coloured beads will become concentrated at the test strip turning it blue |
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Describe how monoclonal antibodies are used to test for HIV. |
1) HIV antigens are bound to the bottom of a well plate 2) The patients blood plasma is added. If there are any HIV antibodies these will bind to the antigen 3) The well is washed out and another antibody with an enzyme attached is added. This will attach to the primary antibody 4) The well is washed again and a solution with a substrate is added to the well whch reacts with the enzyme causing it to change colour |
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In a test for HIV why is the well plate washed? |
To remove any unbound antibodies |
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What is HIV? |
A virus that infects and kills the T-helper cells, preventing an immune response |
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When does HIV develop into AIDs? |
When the levels of helper T-cells drop critically low |
