Biology- Unit 1- Immunity

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  • Created by: FireDwarf
  • Created on: 30-11-13 13:40
What are the two types of defence mechanims?
Non-specfic and specific.
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What does non-specific mean?
They dont distingush between diffrent pathogens and have the same responce for them all. They react immediantly.
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Examples of non-specific?
Barriers to entry & phagocytosis.
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They do distiguish and have diffrent mechanims dependant on the pathogen. Less rapid responce but provide long lasting immunity.
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T & B cells (lympohcytes) which provide the cell-mediated responce and the humoral responce.
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Why is it impportant lympocytes reconise their own cells?
So that they do not destroy self cells but instead target non-self cells.
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How do they achieve reconising their own?
In fetus, we only usually have our own self cells because we are protected. Lympocytes therefore collide exclusivly with our own cells. Those who have receptors which are complentory with our cells are repressed/desroyed.
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Give some examples of physical barriers?
Skin, hydrachloric acid in the stomach, mucus in the trachea.
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What type of cell are phagocytes?
White blood cells.
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How does phagacytosis occur?
phagocyte is attracted to the pathogen via chemicals released from the pathogen. Moves towards it. Attract themself to the surface of pathogen and engulf it forming a phagosome. lysosomes move towards the phagosome and fuse with it. They release
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digestive enzymes which hydrolyse the pathogen in a catabolic reaction into smaller molecules. These are absorbed by the cytoplasm of the phagocyre.
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How do we get inflamation and why do we get puss?
inflamation is due to histamine, which dilates our blood vessels so the phagocyte can get there faster. Puss is dead phagogens or phagocytes.
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What is an antigen?
A part of a organisim or substance which is reconised as non-self by the immune system and stimulates an immume responce. Usually part of the cell surface membrane or cell walls of invading cells, or diseased cells.
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Where are T cells produced? What type of immunity do they provide?
In the thymus gland & cell-mediated immunity.
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When do T cells respond?
They respond to the bodies own cells which have become invaded lby non-self material or transplated material.
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What are the diffrences between B cells and T cells?
B produce antibodies, T dont. T only present to cells which have the antigen on their surface membrane (antigen-presenting cells).
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How do T cells therefore know when to respond?
Cells which have become infected take the antigens from the pathogen and present them on their cell surface membrane, becoming antigen-presenting cells.
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Describe what occurs when a phaogcyte becomes infected.
When the phagocyte becomes infected, it will take the antigen from the pathogen and present it on its membrane, becoming a antigen presenting cell. If a T helper cell has receptors which are complementory to the shape of the antigen, it will form a
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compex. It will then begin to divde rapidly via mitosis into other cells, such as memory cells, suppressor t cells etc. Will also kill infected cell and stimulate b cells to divide.
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How do T cells kill infected cells?
They produce a protien which makes a hole in the cell-surface membrane. This causes the cell to be freely permeble to all substances and dies. Most effective agianst viruses because they need cell to survive.
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What type of immunity do b cells provide?
Humoral immunity.
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Why are there lots of diffrent types of b cells?
Because each one has antibodies which are complementory to a specific antigen on a specific pathogen.
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What occurs when a pathogen is inside the blood stream?
The pathogen will come into contact with many b cells. When a b cell with a complementory antibody to the antigen collides with the pathogen, it will form the antigen-antibody complex. This triggers the b cell to divide via mitosi to produce
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identical b cells with the antibodies to bind with the specfic antigen.
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When it divides, what types of cells do they produce?
Plasma cells and Memrory cells
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Plasma cells? What do they do? What do they provide?
Secrete antibodies directly. These destroy the pathogen and toxins. Primary immune responce.
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Memory cells?
Circulate in blood and fluid. Encounter pathogen at later date, divide rapidly. Provide secondary immune responce and long lasting immunity.
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why are memory cells more effective then b cells?
Because they are n higher frequency, therefore more likely to collide with the complemntory antigen of the pathogen and therefore more likely to produce the antibodies needed to destroy the non-self pathoen.
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What is an antibody?
A protien synthesised by B cells.
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Why are antibodies specific?
Antibodies are specfic because they bind with a specfic anti-gen to form a antibody-antigen complex. Therefore their shapes must be compllementory of each other for this to occur, so therefore the antibody must have specific shape .
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What are the chains called?
Heavy and light chains.
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How can the antibody fit around the antigen?
Change their shape by moving as if they had a hinge at the fork of the Y shape.
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What is the variable region?
The region of the antigen which changes on each antigen, to form the binding site for the complex. It must change to be complementory of the diffrent shapes antigens..
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What is the constant region?
Binds to receptors on cells such as B cells, same in all antibodies.
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What is a polyclonal antibody?
a group of antibodies fighting agianst a single pathogen.
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What is a monoclonal antibody?
A specfic antibody to one specific antigen.
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how are monoclonal antibodies useful?
immunoassay, calculating amounts of substance, cancer treamtnet and transplant surgery.
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Passive vaccination?
Introduction of antibodies by an outside source. They are not replaced whgen they get broken down, short lived immunity.
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Active immunity?
Stimulate body to produce their own antibodies, long lasting.
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What are the two types of immunity?
Passive & Active
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Introduction of antibodies into the individual by an outside source. Short lived as they are not replaced when broken down.
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Stimulate the production of the antibodies by their own immune system. Long lasting.
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What is a vaccination?
Introduction of a weak or dead pathogen with the intention of stimulating an active immunity agianst a specific disease.
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What makes vacinations successful?
Economically avaliabl to immunisize all vunerable population, few side effects, production,storeage and delivery, administration at appopiate times.
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What is herd immunity?
Vaccinating all/most of the vunverable people to cause the disease to be unable to spread. If you do it when nobody has the disease then the disease will be interupted in trasnmission.
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Why can vaccinations not eliminate a disease?
Fails to ummunitize us all, may actually get the diease after vaccination, pathogen may mutate frequently, mass varities, hide from immune system, not everyone accepts vacinations.
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Problems of controlling cholera via vaccination?
Cholera, intestinal dieass and cant be reached easilly by immune system. Their antigens also change rapidly.
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tubercilosis ?
Increase in HIV causes lower immune systems. Refugges due to war are moving aroumd. Mobile populations. Increase in elderly.
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What does non-specific mean?


They dont distingush between diffrent pathogens and have the same responce for them all. They react immediantly.

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Examples of non-specific?


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