Unit 1: Section 1 DISEASE

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1. Disease

Causes of disease
~ Infectious, ie pathogens, bacteria and viruses eg common cold
~ non-infectious, caused by body malfunctioning ie cancer or lifestyle ie malnutrition

Diseases affected by lifestyle
increases the chance of getting a disease ie smoking, drinking = risk factor
ie. Coronary heart disease and cancer

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2. Pathogens, give examples

Viruses - HIV, Rhinovirus, Influenze virus

Bacteria - E. Coli, Cholera, TB

Fungi- Thrush, Athletes foot

A disease causing micro organism that hibits an immune response within the body

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2. How do pathogens enter the body?

through organisms interface with the enviroment

Gas exchange system-
Breathe in air that contains pathogens, get trapped in mucus lining in the lung epithelium
Goblet cells also have cilia, - move the mucus up to the mouth ; where its removed
some pathogens still reach the alveoli

The skin-damage to the skin, patgogens on the surface enter bloodstream
blood clots to form a scab to prevent more pathogens from entering

The digestive system-
consume material that contains pathogens
most killed by stomach acid
some may survive and pass to the intestine where they invade cells of the gut wall

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2. How pathogens cause disease?

Production of toxins-
bacteria release toxins into the body

cell damage-
damage host cells by
~rupturing them to release nutrients inside them
~starves the cell - ie. breaking down nutrients inside the cell
~replicating inside the cells and bursting them when theyre released

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3. How is the immune response activated?

When a pathogen invades the body, antigens on the cell surface of the pathogen are identified as foreign

 Antigens = molecules on a pathogens cell surface

Antigens are proteins

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3. The first stage of the immune response


A phagocyte is a type of white blood cell
Phagocytosis is the engulfment of pathogens

1. A phagocyte recognises the antigens on a pathogen
2. the cytoplasm of the phagocyte moves round the pathogen= engulfing it
3. The pathogen is now conatined in the phagocytic vacuole in the cytoplasm of the phagocyte
4. A lysosome fuses with the phagocytic vacuole. the lysosomal enzymes break down the pathogens.
5. the phagocyte then presents the pathogens antigens - it sticks the antigens on its surface to activate other immune system cells

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3. the second stage of the immune response

T-cell activation

white blood cell
the proteins on its surface bind to antigens presented by phagocytes -  activates the t-cell

some T-cells release substances to activate T-cells
some T-cells attach to antigens on a pathogen and kill the cell

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3. the third stage of the immune repsonse

B-cell activation and plasma cell production

white blood cell
covered with antibodies (proteins)
Antibodies bind with antigens to form an antigen-antibody complex
each B-cell has different shaped antibody on its membrane, so different ones bind to different antigens

when the complimentary antibody and antigen meet, they bind
this, (with substances from T-cells) activates the B-cell
the B-cell then divides to produce many B-cells called plasma cells

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3. The fourth stage of the immune response

Antibody production

plasma cells are identical to B-cells
They secrete antibodies specific to the antigen.

Antibody function includes-
~coating the pathogen to make it easier for phagocytosis
~coating the pathogen to prevent it from entering host cells
~binding to and neutralising toxins produced by the pathogen

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3. What is the structure of an antibody like?


specificty depends on variable regions
each antibody has a different varaible region thats specifc to 1 specific antigen

the constant regions are always the same

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3. what are the four types of immune response?

1. Cellular repsonse- the T-cells form this response
2. Humoral response- B-cells and the production of antibodies form this
     both types of response are needed to remove a pathogen
     responses interact with each other ie. T-cells activate B-cells

3. Primary response- ~antigens enter the body for the first time, it activates the immune response
                                  ~ slow response- arent many B-cells that can make the antibody needed to bind to the pathogens antibody
                                   ~ after being exposed to the antigen, T and B-cells produce memory cells
                                   ~ second time exposure, there is a quicker response as memory T and B-cells remember the specific antigen and will bind to it the second time around

Secondary response- ~quicker stronger immune response, gets rid  of pathogen before any symptoms are shown
                                   ~ memory B-cells divide into plasma cells that produce the right antibody 
                                   ~memory T-cells divide into the correct T-cells to kill the pathogen

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4. Vaccines , how do they work?

vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing the individual disease - no symptoms

vaccines priotect people with the vaccine , and because the reduce the occurence of disease , those not vaccinated are less likely to catch the disease    = this is called herd immunity

vaccines contain antigens attached to dead or weakened pathogens

vaccines may be injected or taken orally,  if taken orally it can be broken down by enzymes in the gut
sometimes booster vaccines are given to make sure memory cells are still produced

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5. what is antigenic variation?

When pathogens change their surface antigens

antigenic variation means that when infected for the second time, the memory cells  from the 1st infection will not recognise the pathogens antigens.
immune system has to start again = new primary response

antigenic variation makes the producyion of vaccines difficult

an example of antigenic variation is the influenza virus (flu)

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6. What are monoclonal antibodies?

antibodies produced from a single group of genetically identical B-cells

all identical in ther structure

not like normal antibodies as they can be made to bind to anything that you want as opposed to a very specific antigen

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