preventing and treating disease

• give 4 ways in which the spread of pathogens can be reduced:

  • hygiene - handwashing, disinfectants, tissues
  • reducing contact with infected individuals - quarantine
  • removing vectors - use of pesticides and insecticides, removal of habitats
  • vaccination
• why is it important to prevent the spread of viral diseases?

  scientists have not yet developed cures for many viral diseases
• how can HIV/AIDS be prevented?

  • use of condoms
  • screening of blood for transfusions
  • not sharing needles
  • use of antiretroviral drugs to prevent the development of AIDS
• how can the spread of salmonella be limited?

  • vaccinating animals intended for consumption
  • keep raw meat away from cooked meat
  • thoroughly cook meat
• how can rose black spot be treated?

  • using fungicides
  • destroying infected leaves
• how can the spread of malaria be reduced?

  • using insecticides
  • using insect nets to avoid bites
  • prevent mosquito breeding by removing stagnant water
  • antimalarial drugs
• how can the skin prevent pathogens from entering the body?

  • the skin acts as a physical barrier
  • scab formation after skin is cut/wounded
  • antimicrobial secretions which can kill pathogens
• how does the respiratory system prevent pathogens from entering the body?

  • nose - has hairs and mucus which trap pathogens
  • trachea and bronchi - have mucus that traps pathogens. ciliated cells move mucus to the mouth so it can be swallowed
• how does the stomach prevent pathogens from entering the body?

  -secretes hydrochloric acid which kills any pathogens present
• how does phagocytosis protect us against disease?

  white blood cells ingest and destroy pathogens so they cannot infect more cells
• how does antibody production protect us against disease?

  • white blood cells produce antigens which are complementary to a specific antigen on a pathogen
  • the binding of antibodies to antigens causes pathogens to clump together, making them easier to destroy
  • in the case of a 2nd infection, the correct antibodies can be produced rapidly, preventing the person getting the same disease again
• how does antitoxin production protect us against disease?

  antitoxins bind to toxins released by pathogens and neutralise them
• vaccination


  contains a dead or inactive pathogen which stimulates white blood cells to produce complementary antibodies to the pathogen in the case of a second infection, memory cells can rapidly produce the correct antibodies and prevent illness
• herd immunity


  a sufficiently high proportion of a population which are immune to a disease, the spread of a disease will be limited
• advantages of vaccination

  • have eradicated many deadly diseases
  • epidemics can be prevented
  • herd immunity protects those who cannot have vaccinations
• disadvantages of vaccinations

  • not guaranteed to work - might not protect against multiple strains of a pathogen
  • may be side effects or adverse reactions
• how are bacterial diseases cured?

  with antibiotics that kill pathogens inside the body
• how do antibiotics work?

  kill bacterial pathogens inside the body, but will not kill human cells
• why do antibiotics not work to treat viral diseases?

  they have no effect on viral pathogens as they live inside the host's cells; therefore it is difficult to design drugs that would kill the virus and not destroy human cells at the same time
• antibiotic resistance


  occurs when mutations lead to individua bacteria being resistant to an antibiotic. these bacteria are able to survive, reproduce and pass on their alleles, leading to a greater proportion of antibiotic-resistant bacteria
• how can we prevent antibiotic resistance

  • avoid overuse and unnecessary use of antibiotics - e.g. only prescribe them for viral infections
  • finish the full course to ensure all bacteria is killed
• painkillers -> infectious diseases

  only treat the symptoms but do not kill pathogens
• what plant is digitalis extracted from?

  foxgloves
• what painkiller originates from a willow bark tree?

  aspirin
• what antibiotic was discovered by fleming?

  penicillin
• what are the 4 qualities of a good medicine?

  • safe
  • effective
  • stable
  • able to be taken in and removed easily
• what 3 factors are tested when developing new drugs?

  • toxicity
  • efficacy
  • dosage
• preclinical testing


  -carried out in a lab

  -uses cells, tissues and live animals
• clinical testing


  -uses healthy volunteers and patients

  1. drugs are tested at a low dose on healthy people
  2. then on patients and at a larger scale to find the optimum dose
  3. often, one group receives a placebo and another group receive the actual drug in order to assess the efficacy
• single-blind trial


  only a doctor knows whether the patient is receiving the drug or the placebo
• double-blind trial


  neither the patients nor doctors know who gets what

  -helps removes bias
• peer review

  where the results of drug trials are checked over by the scientists knowledgeable in this field