Infection and Response - CHAPTER 3

• what is a pathogen ?

  a microorganism that cause infectious disease
• how do pathogens make us ill ?

  pathogen produce toxins which causes damage to the cells
• name all four pathogens

  bacteria, fungi, virus, protist
• how do protist infect the body ?

  some protists are parasite. Parasites live on or inside other organisms and cause them damage
• how can bacteria make people feel ill

  by producing toxins which damages cells and tissue
• how do pathogens spread ?

  through touch, through water (cholera), through air
• name viral diseases

  HIV, Measles, TMV
• how do viruses infect the body ?

  viruses live inside the cells and replicate themselves using the cells' machinery to produce many copies of themselves. The cell burst releasing all the viruses which cause damages to the cells
• what are the symptoms of measles ?

  fever and red rash
• measles : spread by

  droplet infection
• measles : control

  vaccinations against disease (MMR vaccine)
• HIV: symptoms 


  flu-like symptoms
• HIV: spread by sexual contact or exchange of bodily fluids

  sexual contact or exchange of bodily fluids
• HIV: control

  antiretroviral drugs
• name bacterial diseases

  salmonella and gonorrhoea
• Gonorrhoea: spreads by

  sexual contact
• Gonorrhoea: symptoms

  thick yellow or green discharge from vagina or penis, pain when urinating
• Gonorrhoea: controlled by

  treatment with antibiotics, use a barrier of contraception such as condoms, abstaining from sex
• Salmonella: spread by

  ingesting contaminated food with salmonella bacteria
• Salmonella: symptoms

  fever, abdominal pain, vomiting, diarrhoea
• salmonella: controlled by 


  vaccinating poultry, wash hands, preparing food in hygenic conditions
• TMV: spread by

  contaminated equipment
• TMV: symptoms

  discoloured leaves
• TMV: control by

  removal of weeds that could have TMV
• name a fungal disease

  rose black spot
• rose black spot: spread by

  spores which are released in wet humid conditions
• rose black spot : symptoms

  leaves turn yellow around spots, black or purple spots, small black scab like spots develop on young cells
• rose black spot : controlled by

  burning shoots in spring and burning all cut stems, fungicides, not composting infected plants
• name a protist disease

  malaria
• malaria: spread by

  mosquito which is the vector bites an animal affected with malaria and sucks up the plasmodium and bites someone who isn't already affected with malaria
• malaria symptoms :

  headaches, chills, flu-like symptoms, sweat, diarrhoea, coughs, aches, fever
• malaria: control 


  sleeping under a mosquito net, bug spray, preventing mosquitos from breeding
• ways to reduce the risk of infectious disease

  improved hygiene such as washing hands and cleaning surfaces, vaccination against infectious diseases, killing the vectors that carry the pathogens, isolating or quarantining people who are infected
• WAYS THE BODY DEFENDS ITSELF FROM PATHOGENS

  The skin acts as a barrier to pathogens. It secrete antimicrobial substances which kill pathogens. Hairs and mucus in the nose traps particles that contain pathogens. The trachea and bronchi secrete mucus to trap pathogens. The trachea and bronchi are lined with cilia, which are hair - like substances which waft mucus up to the back of the throat to be swallowed. The stomach produces hydrochloric acid which kills pathogens that make it that far from the mouth.
• Phagocytosis


  white blood cells engulf foreign cells and digest them. Every pathogen has a unique molecule called antigen on its surface. When the white blood cell comes across a foreign, they produce proteins and antibodies to lock onto invading cells so they could be found and destroyed by other white blood cells. Antibodies are specific to that type of antigen. Antibodies are produced rapidly to find similar bacteria and viruses. If the person is infected with that same pathogen, WBC will produce antibodies that kill it and the person will become naturally immune
• what is a vaccination ?

  small amount of dead or inactive pathogens
• How do vaccines work ?

  they expose us to antigens of a pathogen so that we can develop immunity from it.
• Positives of vaccinations


  vaccines help control lots of common communicable diseases in the UK. It also prevents big outbreaks of the disease called epidemics - it is a large percentage of people are vaccinated and therefore those who don't have it are less likely to have it
• Negatives of vaccinations

  Doesn't always give gull immunity to the disease. It can cause bad reactions like swelling or even more serious like fevers or severe symptoms like seizures
• what is anti-biotic resistance ?

  when bacteria can evolve so that anti-biotics no longer kill them