B3: infection and response

• pathogens - microorganisms that cause disease which spread between organisms
• rose black spot is a fungal disease spread in water and wind causing purple black spots on leaves and is treated by fungicides or removing infected leaves
• malaria is caused by a protist spread by mosquitoes causing fever and death sometimes and is prevented by stopping mosquitoes breeding or mosquito nets
• salmonella food poisoning is caused by bacteria due to contaminated food and causes fever, vomiting, diarrhoea, cramps and is treated by vaccination on meat and prevented by hygienic food prep
• gonorrhoea is caused by bacteria during intercourse and causes pain in urination, yellow green discharge from vagina or penis and is treated by antibiotics and prevented by condoms
• Measles is a viral infection spread by airborne droplets (coughs/sneezes) and causes fever, rashes and death sometimes and is prevented by vaccinating children
• HIV is a viral infection due to intercourse or exchange of bodily fluids and initially causes a flu but damages the immune system and later can cause AIDS, prevented by condoms and avoiding sharing needles
• tobacco mosaic virus causes a mosaic pattern on leaves which reduces photosynthesis and growth
• 4 defences against pathogens:

  1. skin - barrier and secrets antimicrobial substances to kill pathogens
  2. trachea and bronchi - mucus traps pathogens and cilia waft mucus up to the throat to be swallowed
  3. nose - hairs and mucus trap pathogens
  4. stomach - hydrochloric acid kills pathogens
• phagocytosis - white blood cell engulfs pathogen and digests it
• producing antibodies - white blood cells produce specific antibodies for pathogen and antibodies then attack all pathogen’s antigens in the body
• white blood cells also produce antitoxins to neutralise toxins produced by bacteria
• vaccinating a large population reduces spread of pathogens so even unvaccinated are less likely to catch disease
• vaccination:

  1. dead or inactive pathogens inserted
  2. white blood cells produce specific antibodies
  3. if live pathogens try to attack, they are quickly recognised and attacked
• antibiotics kill bacteria and specific antibiotics kill specific bacteria
• pain killers treat symptoms of disease but don’t kill pathogens
• the drug digitalis is a heart drug produced by foxgloves
• the drug aspirin is a painkiller produced by willow
• the drug penicillin is an antibiotic produced by penicillin mould
• new drugs are trailed for safety and effectiveness in 3 ways:

  1. toxicity - how harmful
  2. efficacy - whether drug works and produces right effect
  3. dosage - concentration that should be given and how often
• preclinical testing (tests on human cells, tissues and live animals)> clinical trials (test on healthy volunteers, gradually increased> then tested on ill patients for correct dosage> peer review)
• clinical trials often double bind (3 given drug and 3 given placebos)
• placebos- substances that are like the drug being tested but don‘t do anything