infection and response

• pathogens are microorganisms that cause infectious diseases
• • bacteria = reproduces rapidly and release toxins (harmful chemicals) damages tissues and makes us feel ill
  • viruses = invades the host cell and reproduces in it causing it to burst
• spreading of pathogens

  • water droplets
  • directly in water
  • direct contact
• reduce spread of pathogens

  • basic hygiene (washing hands)
  • clean drinking water
  • reduce direct contact
  • patients may be isolated
  • vaccinations
• measles

  • symptoms: fever, skin rashes
  • spread in droplets (coughs and sneezes)
  • can damages breathing system and the brain
  • children are vaccinated
• HIV

  • symptoms: flu-like illness
  • attacks immune system and unables it to fight off other infections and cancer cells
  • patient may develop cancer (fatal)
  • treated using antiretroviral drugs which stops virus from multiplying inside patient leading to a normal life expectancy
  • spread b unprotected sexual intercourse or sharing infected needles
• viruses cannot be fought off by antibiotics
• bacteria can be killed by antibiotics
• salmonella food poisoning

  • spread by ingesting infected food, unhygienic conditions
  • bacteria secrete toxins
  • symptoms: fever, vomiting, abdominal cramps and diarrhoea
  • vaccinations
• gonorrhoea

  • sexually transmitted (STD)
  • symptoms: thick yellow/green discharge from the penis or vagina, pain when urinating
  • treated antibiotic penicillin
  • reducing spread by using a condom, people who have unprotected sex should be tested to be treated by antibiotics before it is passed on
• malaria

  • protist
  • symptoms: repeated bouts of fever
  • mosquito carries pathogen from one person to another
  • reducing spread of malaria (preventing them from breeding) by draining or spraying insecticides on areas of still water, sleep under mosquito net
• non-specific defence system

  • skin = protective layer, dead cells (difficult for pathogens to enter), sebum kills bacteria
  • nose = hair and mucus trap pathogens
  • lungs = trachea and bronchi are covered in cilia (tiny hairs) with mucus which is swallowed into the stomach
  • stomach = hydrochloric acids kill pathogens
  • immune system
• immune system

  • phagocytosis - white blood cells can ingest using enzymes to destroy pathogens
  • antibodies (specific) (remain in the blood for a long time)- protein molecules produces from white blood cells which stick to pathogens triggering it to be destroyed
  • antitoxins = stick to a toxin and prevents them from damaging cells
• TMV

  • widespread (tomatoes)
  • symptoms: discolouration in a mosaic pattern, rate of photosynthesis and growth of plant is reduced
• rose black spot (fungus)

  • purple of black spots whihc turn yellow and fall off
  • photosynthesis growth decreases
  • treated by spraying chemicals (fungicides) to kill fungus or remove the infected leaves and destroy them
  • spread by wind or water
• vaccination involve small quantities of dead or inactive forms of pathogens into the body

  • white blood cell is stimulated to produce antibodies
  • white blood cells divides by mitosis
  • if same pathogen enters the body, white blood cells will produce the correct antibodies quickly, preventing infections
• herd immunity is when there is a person which has not being vaccinated amongst a lot of people who were vaccinated meaning they cannot be infected
• antibiotic resistance

  • bacteria which have evolved
  • antibiotics cannot kill viruses
  • painkillers relieve the symptoms but the pathogen is not killed
• testing medicines

  • check toxicity, effectiveness and best dose
  • pre-clinical testing is carried out on cells, tissues, or live animals which is then tested on humans with very low doses to check if the drug is safe
  • placebo is a tablet or injection with no active drug
• double-blind trial

  • test group receives active drug
  • placebo group receive a dummy drug with no active ingredient
  • neither the patients nor the doctors know whihc people have the active drug and placebo to stop bias