topic 3 infection and response

• What are pathogens?

  microorganisms that cause disease. these include protists, bacteria, viruses and fungi. they can spread through air, direct contact or water
• Describe viruses and how they work (4)

  - They are very small

  - They move into cells and use the biochemistry to multiply copies of itself

  - Consequently, the cell bursts. All of the copies are then released into the bloodstream.

  - This damage and destruction makes people feel ill

  - Not living
• Describe bacteria (4)

  - They are very small

  - Unicellular

  - Multiply very quickly through dividing by binary fission

  - Produce toxins, which are poisonous.
• Describe protists (2)

  - unicellular eukaryotes

  - they are often parasitic; this means they use a host, either a human or an animal (live on or inside, causing damage)
• Describe fungi

  - Can either be single celled or have a body made of hyphae

  - Can produce spores which can spread to other plants (2)
• Name 3 ways these can spread and 1 example of one of these

  - direct contact

  - water

  - air (an example of this would be Droplet Infection, which is where pathogens are expulsed ie through coughing, sneezing or talking in the form of droplets)
• how can pathogens be limited?

  - hygiene, ie, washing hands thoroughly

  - reducing contact with infected individuals

  - vaccinations (small bit of pathogen injected to bring about immunity)

  - removing vectors ie through pesticides
• why are viruses dangerous

  can enter all types of cell

  scientists have not found a cure
• Measles: how is it spread, what are the symptoms and how is it prevented?

  symptom's: fever and red skin rash, blindness, brain infection and pneumonia

  spread: droplet infection

  how is it prevented: vaccinations
• HIV: s, s, p

  symptons: inititally flu like symptons then the immune system is attacked and person develops AIDS (state where body is susceptible to many different diseases)

  spread: through sexual contact or exchange of bodily fluids eg blood

  prevented: stop spread, ie use condoms

  or take drugs to stop AIDS in the body
• tobacco mosaic virus: s,s,p

  symptons: plant does not grow properly, discoloration of leaves. affected part of plant causes reduced photosynthesis causing reduced yeast yield

  spread: through infected plants, insects act as vectors

  prevented: good field hygiene, use of antipesticides
• BACTERIAL DISEASES. Samonella; s, s, p

  symptons: diarhhea, vomitting, stomach cramps, fever (all caused by the toxins secreted by the bacteria that lives in the gut)

  spread: through diseased raw eggs or meat

  prevented: vaccination of poultry, keep raw meat away from cooked, wash hands etc
• gonorrhea, s, s, p

  symptons: thick green or yellow discharge from vag or penis

  spread: unprotected sex

  prevented: use of protection. antibiotics may be used but many resistant strains are developing
• FUNGAL DISEASES. rose black spot; s, s, p

  symptons: there are purple or black spots on the plants leaves. these affected areas cannot photosynthesize, meaning leaves turn yellow and drop early

  spread: the spores of the fungus are carriedcthrough rain by wind

  prevented: strip leaves of affected plants, fungicides
• PROTIST DISEASES. Malaria: s,s,p

  caused by protist pathogens that enter red blood cells and damage them

  symptons: fever and shaking, when protists burst red blood cells

  spread: the female mosquito anepheles is the vector, in which the protists reproduce sexually. when they suck on human skin, the pathogens enter the human bloodstream via the saliva

  prevented: mosquito nets above beds, travellers take antimalarial drugs, remove stagnant water to prevent vectors from breeding
• explain how the non specific defence system in the human body works against pathogens

  SKIN: acts as a physical barrier. produces antimicrobial secretions

  NOSE: has hair and produces mucus to prevent pathogens entering lungs

  TRACHEA AND BRONCHI: secrete mucus to trap pathogens

  have cilia which waft mucus upwards so it can be swallowed

  STOMACH: hydrochloric acid which kills any pathogens
• a large part of the specific immune system is the white blood cells. explain phagocytosis

  Engulfing and consuming of pathogens.

  This destroys them, so they can no longer make you feel ill.
• explain antibodies

  each pathogen has an antigen on its surface, which is a structure that can bind to a specific antibody. once antibodies bind, the pathogens clump so that they are easier to find.

  if you then become infected again with the same pathogen, the same antibodies will be produced FASTER so that the person will not feel ill and is said to be immune. this is known as secondary immune response, and is reliant on memory cells.
• explain antitoxins

  these neutralise the toxins released by the pathogens by binding to them so that the person does not feel ill.
• what is herd immunity

  When a majority of a population are vaccinated against a disease. This means that even people who have not been vaccinated are less likely to get it because there are fewer people to catch it from.
• what do vaccinations do

  they replicate the first infection so that the second immune response is much quicker if it does occur
• explain how they work

  - an inactive or dead form of a pathogen is injected

  - this stimulates an immune response and antibody production

  - memory cells are made against this pathogen

  - if said person encounters the pathogen again in the future, they will be protected, immune.
• advantages and disadvantages of vaccinations?

  advantages: they have eradicated many diseases in the past ie smallpox and have helped reduce the occurence of many others eg rubella

  epidemics can be prevented through herd immunity

  disadvantages: sometimes people have side affect reactions to vaccinations eg fever

  they are also not always effective in providing immunity and protection will fade over time
• what are antibiotics?

  medicines that kill bacterial pathogens within the body without damaging any other cells in the process. they cannot kill viruses because viruses use body cells to reproduce so antibiotics would damage body tissue in the process.
• what are painkillers?

  Drugs that relieve the pain and help reduce the symptoms of a disease
• how can antibiotics be taken

  pill, syrup or directly into the bloodstream
• different ones are...

  effective against different bacteria, so choosing the correct one is v important
• example?

  penicillin
• what is the concern with antibiotics? explain further

  - there are many bacterial diseases that are becoming resistant to antibiotics. this is due to mutations that can occur during reproduction. so when they are exposed to antibiotics, only the non-resistant die, and so the resistant population increases as they survive and reproduce. so previously effective antibiotics no longer work.
• to prevent this, we can?

  - stop overusing antibiotics to stop them all being exposed to too much

  - finish courses of antibiotics so all bacteria is killed
• how and why do drugs need to be tested?

  they needed to be tested to check their efficiency and toxicity and dose.

  this is done by pre-clinical and clinical trials
• explain preclinical and clinical testing

  preclinical: using tissues, cells and live animals

  clinical: using volunteers and patients

  - it is first tested on healthy volunteers to ensure no side affects

  - then tested on patients to find most effective dose

  - then to test how well it works, patients are split into two groups. one are given actual drug adn one are given placebo so the effect of the actual drug can be observed.

  - these can be single blind (only doctor knows) or double blind (neither doctor nor patient knows)

  - these results then need to be peer reviewed by other scientists to check repeatability
• plant drugs: two examples and explanations

  aspirin (painkiller that originates from willow)

  digitalis (treats heart problems and originates from foxglove)
• penicillin?

  A.Fleming was growing bacteria on plates. he left them and came back to find mould on these plates, with clear rings around the mould indicating no bacteria there. he found the mould was producing penicillin, which kills bacteria.
• what are monoclonal antibodies?

  Antibodies produced from a single group of genetically identical B-cells
• How are monoclonal antibodies produced?

  - scientists obtain mice lympocytes (make antibodies, but cannot divide) and stimulate it to produce a specific antibody.

  - then they are combined with tumour cells (no antibodies, but divide rapidly) to produce a cell called a hybridoma.

  - the hybridoma can produce clones of itself which all produce same antibody

  - cloned and collected and purified
• explain pregnancy tests

  - hormone called hCG is present in females who are pregnant

  - two sections of stick. first has MOBILE antibodies that are COMPLEMENTARY TO hCG. also attached to blue beads.

  - section section has STATIONARY antibodies that are also complementary to the hCG hormone which is stuck down the stick.

  - woman pees on stick. if hCG is present, then it binds and forms antibody/hCG complex.

  - carried in flow of liquid to stationary section.

  - stationary antibodies bind to the complex.

  - as they are each bound to a blue bead, a blue line is formed.

  - this line indicates pregnancy
• how are monoclonal antibodies used in labatories?

  to measure and monitor levels of hormones or chemicals in the blood.

  - antibodies are modified so they will bind to the molecule you're looking for.

  - antibodies are also bound to a fluorescent dye.

  - if molecules are in sample, they bind and the dye can be observed.

  - this method can also be used to find or identify molecules of a certain cell or tissue
• how can MA help cancer?


  - cancer cells have antigens on them known as tumour markers. there are three ways.

  - antibodies bind to antigen so cancer cells can be targeted.

  - antibodies bind to the receptor site so that growth stimulating cells cannot bind so cell cannot divide.

  - MA can transport drugs or toxic chemicals cos they can only bind to cancer cells.
• advs and disadvs of MA?

  ads:

  only bind to specific cells, so healthy cells arent affected

  engineered to treat many different conditons

  scientists can now produce a mouse-human hybrid cells to reduce the risk of an immune resposne

  disads:

  difficult to attach to drugs

  expensive

  often trigger immune response bc they are from mice