1.3 infection and response

• What is a communicable disease?


  A disease caused by a pathogen which can be passed between animals or plants.
• What is a pathogen?


  A disease-causing microorganism.
• How do bacteria cause disease?


  They divide rapidly by binary fission, kill cells, and produce harmful toxins.
• What are three ways in which pathogens can be spread?


  • By air (e.g., flu, tuberculosis)
  • By water (e.g., fungal spores in water)
  • By direct contact (e.g., sexually transmitted infections)
• How do viruses cause disease?


  They invade and reproduce inside living body cells, leading to cell damage.
• What are four ways in which the spread of pathogens can be reduced?

  • Hygiene (handwashing, disinfectants)
  • Reducing contact with infected individuals (quarantine)
  • Removing vectors (pesticides, insecticides)
  • Vaccination
• Why is it especially important to prevent the spread of viral diseases?


  Scientists have not yet developed cures for many viral diseases.
• What is measles?


  A serious viral disease that can cause blindness and brain damage.
• How is measles spread?


  By air through inhalation of droplets from coughs and sneezes.
• What is HIV/AIDS?


  HIV is a virus that attacks the immune system, leading to AIDS.
• How is HIV spread?


  Through direct sexual contact and the exchange of bodily fluids.
• How can the spread of HIV/AIDS be prevented?


  • Use of condoms
  • Screening of blood for transfusions
  • Not sharing needles
  • Bottle-feeding by HIV-positive mothers
  • Use of antiretroviral drugs
• What is tobacco mosaic virus?


  A plant pathogen that causes leaf discolouration.
• How is tobacco mosaic virus spread?


  Through contact between infected and healthy plants, often by insects as vectors.
• What is salmonella?


  A type of bacteria found in raw meat, poultry, and eggs.
• What are the symptoms of salmonella food poisoning?


  • Fever
  • Abdominal cramping
  • Vomiting
  • Diarrhoea
• How can the spread of salmonella be limited?


  • Vaccinating animals intended for consumption
  • Keeping raw meat away from cooked meat
  • Disinfecting hands and surfaces after contact with raw meat
  • Thoroughly cooking meat
• What is gonorrhoea?


  A sexually transmitted bacterial infection caused by unprotected sex.
• What is rose black spot?


  A fungal disease causing purple or black spots on rose leaves.
• How is the rose black spot fungus spread?


  Fungal spores are spread by wind and in water.
• How can the rose black spot fungus be treated?


  • Using fungicides
  • Destroying infected leaves
• What is malaria?


  A disease caused by protist pathogens carried by mosquitoes.
• How can the spread of malaria be reduced?

  • Using insecticides
  • Using insect nets
  • Preventing mosquito breeding
  • Antimalarial drugs
• How does the skin prevent pathogens from entering the body?


  • Acts as a physical barrier
  • Scab formation after cuts
  • Antimicrobial secretions
  • Healthy skin flora compete with pathogens
• How does the respiratory system prevent pathogens from entering the body?


  • Nose has hairs and mucus
  • Trachea and bronchi have mucus and ciliated cells
• How does the stomach prevent pathogens from infecting the body?


  • Secretes hydrochloric acid to kill pathogens
• How does phagocytosis protect us against disease?


  White blood cells ingest and destroy pathogens.
• How does antibody production protect us against disease?


  Antibodies bind to antigens on pathogens, clumping them together for destruction.
• How does antitoxin production protect us against disease?


  Antitoxins bind to toxins released by pathogens and neutralize them.
• What is a vaccination?


  Contains a dead or inactivated form of the pathogen to stimulate antibody production.
• What is herd immunity?


  If a high proportion of a population is immune, the spread of disease is limited.
• What are the disadvantages of vaccinations?


  • Not guaranteed to work
  • Possible side effects or adverse reactions
• What are the advantages of vaccinations?


  • Eradicated many deadly diseases (e.g., smallpox)
  • Prevented many epidemics
  • Herd immunity protects those who cannot be vaccinated
• What drugs are used to cure some bacterial diseases?


  Antibiotics.
• How do antibiotics work?


  They kill bacterial pathogens inside the body without harming human cells.
• Why can antibiotics not be used to treat viral diseases?


  Antibiotics have no effect on viral pathogens as they live inside host cells.
• What is antibiotic resistance?


  It occurs when mutations lead to bacteria being resistant to antibiotics.
• How can we prevent antibiotic resistance?


  • Avoid overuse of antibiotics
  • Finish antibiotic courses
• What effect do painkillers have on infectious diseases?


  Painkillers treat symptoms but do not kill pathogens.
• What plant is the heart drug digitalis extracted from?

  Foxgloves.