Infection and Response

• What is a communicable disease?

  A disease that can be transmitted from one person to another.
• What is a pathogen?

  A microorganism which causes disease
• How do bacteria cause disease?

  They divide rapidly by binary fission. They produce harmful toxins and kill cells.
• What is binary fission?

  A form of asexual reproduction in which a single organism divides into two equal parts, each of which becomes a new individual.
• How do viruses cause disease?

  They inhabit host cells and reproduce inside them causing cell damage.
• Give three ways in which pathogens can be spread.

  By air - flu, tuberculosis, and the common cold are spread by tiny droplets in the air.

  By water - fungal spores in the water spread plant diseases

  By direct contact - common in plant diseases and sexually transmitted infections.
• Give three ways in which pathogens can be spread.

  By air - flu, tuberculosis, and the common cold are spread by tiny droplets in the air.

  By water - fungal spores in the water spread plant diseases

  By direct contact - common in plant diseases and sexually transmitted infections.
• Give four ways the spread of pathogens can be reduced.

  Hygiene - handwashing, disinfectants, tissues.

  Quarantine - Reducing contact with infected individuals

  Removing vectors - use of pesticides and insecticides, removal of habitats

  Vaccination
• Why is it especially important to prevent the spread of viral diseases?

  Scientists have not developed cures for many viral infections
• What is measles?

  Measles is a serious viral disease that can cause blindness and brain damage. The main symptoms are fever and red skin rashes.
• How is measles spread?

  By air droplets
• What is HIV/AIDs

  HIV is a virus which attacks and damages the immune system until it can no longer function properly. AIDs is a condition that develops from long-term HIV. There is no cure/vaccine.
• How is HIV spread?

  Direct sexual contact or exchanging bodily fluids e.g blood or breast milk
• How can the spread of HIV/AIDs be reduced?

  Prevention of HIV/AIDS:

  • Use of condoms
  • Abstinence
  • Screening of blood for transfusions
  • Not sharing needles
  • Bottle Feeding by HIV plus women
  • Use of antiretroviral drugs to prevent the development of AIDs
• What is tobacco Mosiac Virus?

  A plant pathogen which causes leaf discolouration when cells are damaged. Affected areas can not photosynthesise and cause reduced yields. As there is no treatment, farmers grow TMV-resistant crop strains to avoid infection.
• How is Tobacco Mosaic Virus spread?

  Contact between healthy and infected plants. Insects may act as vectors which transfers the virus between plants
• What is salmonella?

  A type of bacteria found in raw meat, eggs and poultry (chicken). Natural gut bacteria are affected if they enter the body via food poisoning.
• What are the symptoms of salmonella food poisoning?

  Nausea, vomiting, diarrhoea, abdominal pain, fever.
• How can the spread of salmonella be reduced?

  Salmonella reduction:

  • Vaccinating animals intended for consumption
  • Keep raw meat away from cooked meat
  • Disinfect hands and surfaces after contact with raw meat
  • Thoroughly cook meat
• What is gonorrhoea?

  A sexually transmitted bacterial infection caused by unprotected sex with an infected individual. Early symptoms include yellow/green discharge from genitals and painful urination, although it may be symptomless.
• How can the spread of gonorrhoea be reduced?

  Through the use of antibiotics, although not penicillin many strains are resistant.

  Using condoms
• What is rose black spot?

  A fungal disease which causes purple or black spots to develop on rose leaves. It reduces the area of the leaf available for photosynthesis and causes a leaf to turn yellow and drop prematurely.
• How is rose black spot spread?

  Fungal spores carried by the water or the wind.
• How can rose black spots be treated?

  Using fungicides

  Destroying infected leaves
• What is malaria?

  A disease caused by protist pathogens, the disease is carried from host to host by the vector mosquitoes, and the protist enters the human bloodstream when bitten. Symptoms include fever and shaking, and may even be fatal.
• 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 does the skin prevent pathogens from entering the body?

  physical barrier

  Scab formation after the skin is cut/wounded

  Antimicrobial secretions which can kill pathogens

  Healthy skin flora competes with pathogens and acts as an additional barrier
• How does the respiratory system prevent pathogens from entering the body?

  Nose - has hairs and mucus which trap pathogens

  Trachea and Bronchi - have mucus which traps pathogens. Ciliated cells move mucus to the mouth so it can be swallowed.
• How does the stomach prevent pathogens from infecting the body

  Secrets hydrochloric acid which kills any pathogens present.
• What is the difference between phagocytes and lymphocytes?

  Phagocytes are white blood cells which circulate in the body. They engulf pathogens and then use a range of enzymes inside the cell to destroy the pathogen. Whereas, lymphocytes recognise specific molecules on the surface of pathogens called antigens.
• How do phagocytes protect us against disease?

  White blood cells (phagocytes) engulf and destroy pathogens so they cannot infect more cells.
• What is an antibody?

  Antibodies are proteins produced by a type of white blood called lymphocytes
• What is a toxin?

  Some bacteria produce toxins that can damage cells and tissues.
• What does the immune system do when a pathogen produces toxins?

  The immune system responds to toxins by producing antitoxins, which neutralise the toxins released by the bacteria and prevent them from causing harm.
• What is a vaccination?

  Contains a dead or weakened version of a pathogen which stimulates the white blood cells to produce complementary antibodies to the pathogen. In the case of a second infection, memory cells rapidly produce the correct antibodies to prevent illness.
• What is herd immunity?

  Resistance to the spread of a contagious disease within a population, is achieved when a large portion of individuals become immune, either through vaccination or previous infection.
• Advantages of vaccinations

  • They have eradicated many deadly diseases like smallpox
  • Prevented many epidemics
  • Herd immunity protects those who can't have vaccines
• What are the disadvantages of vaccinations?

  • Not guaranteed to work - multiple strains of a pathogen
  • May have side effects or adverse reactions
• What drugs are used to cure bacterial infections

  Antibiotics
• How do antibiotics work?

  Antibiotics, like penicillin, kill bacterial cells in the body but not human cells. Some antibiotics kill a wide range of bacteria, it is important the right antibiotic is used for the bacteria