B3 - Infection and Response

• Communicable


  A disease which is able to be transmitted from one sufferer to another.
• Pathogen


  A microorganism that causes infectious disease. Spread by; Direct contact, Water, Air droplets
• Incubation period


  From the second that you catch the disease to the time you start having symptoms.
• Bacteria


  - Multiply by division

  - Produce toxins which make us feel ill (body can produce anti-toxins)
• Viruses


  - Use another organism as a host

  - Invades a cell

  - Replicates inside a cell

  - Causes cell damage (makes us feel ill)
• Measles (Viral)


  - Fever, red skin

  - Spread by inhalation of droplets from coughs and sneezes

  -No treatment, isolation, vaccine
• HIV (Viral)


  - Mild, flu-like illness

  - Spread by direct sexual contact and exchange of body fluids (e.g. blood)

  - Use condoms, blood screening, antiretroviral drugs, not sharing needles
• Tobacco Mosaic Virus (Plant) (Viral)


  - Mosaic pattern of discolouration on leaves

  - Spread by contact between diseased plant material and healthy plants

  - Good hygiene, good pest control
• Salmonella (Bacterial)


  - Fever, vomiting, abdominal cramps, diarrhoea

  - Spread by bacteria ingested in food or food prepared in unhygienic conditions

  - Poultry vaccination, clean surfaces, wash hands, food stored and cooked correctly
• Gonorrhoea(Bacterial)


  - Thick yellow/green discharge from vagina or penis, pain in urination

  - Spread by unprotected sexual contact with an infected person

  - Antibiotics, contraception, reducing number of sexual partners
• Rose black spot (Plant) (Fungal)


  - Purple/black spots on leaves, leaves turn yellow and drop early

  - Spread by the environment, carried by the wind

  - Removing/ burning infected leaves and stems, chemical fungicides
• Malaria (Protist)


  - Recurrent episodes of fever and shaking, can be fatal

  - Spread by mosquitoes (act as vectors) which breed in stagnant water

  - Combination of drugs, insect nets, preventing breeding, insecticides to kill mosquitoes, antimalarial drugs for travellers
• Diseases in plants can be identified by

  Appearance

  Stunted growth
• Function of nitrates in plants


  Needed to make proteins, a lack causes stunted growth
• Function of magnesium in plants


  Needed for making chlorophyll (photosynthesis)
• Mechanical barriers


  - Thorns and hairs

  - Mimicry

  - Leaves that curl up when touched
• Physical barriers


  - Tough waxy cuticle

  - Tough cellulose walls

  - Layers of dead cells around stems
• Chemical barriers


  - Can produce poisons

  - Can produce antibiotics
• Natural killer cells


  Produce poisons to destroy infected cells but also kill nearby cells
• Macrophages (phagocytes)


  Engulf cell debris and destroy it
• Interleukins (chemicals)


  Attract other immune cells to help

  Makes nerves hypersensitive so body aches by the slightest movement and you want to rest

  Trigger the brain thermostat (fever slows pathogens down)
• Dendritic cells (antigen presenting cells)

  Collect and display virus spikes (pathogen antigens)

  Will travel to lymph to find matching T and B cells to find one which might recognise the virus
• T - cells


  Divide and destroy only killing infected cells
• B - cells


  Divide and produce antibodies which target new born virus, holding onto spikes (paralysing virus)
• Memory T and B cells

  Control immunity by memorising virus (remembering same pathogen) and will instantly destroy a re-infection
• Mucus, tears and saliva


  - Pathogens get trapped because it's sticky

  - Have enzymes that digest and destroy pathogens
• Stomach


  Acid destroys most swallowed pathogens
• Trachea


  Little hairs (cilia) waft pathogens and bad things up to the back of the throat to be swallowed into stomach acid
• Skin


  - Covered in bacteria

  - Forming an extra layer of barrier keeping pathogens outside of the body
• Gut


  Competition provided by non-pathogens to prevent pathogens being able to grow
• Edward Jenner


  - Thought if he gave people cowpox, they would be immune to small pox

  - Took pus from a milkmaid suffering from cowpox and gave it to a boy who hadn't suffered from cowpox or small pox, then the boy became immune to smallpox in 1796
• Vaccine


  Contains a dead or a weakened (inactive) pathogen of a small amount. This pathogen doesn't make us ill and stimulates the white blood cells to produce antibodies. If the pathogen enters our body again, the antibodies will act quickly to eliminate the virus.
• Antibody concentration time graph

  
• Drugs can be used to treat disease by

  - Treating symptoms (painkillers, cold remedies)

  - Curing illness (Antibiotics)
• Aspirin


  Willow tree (painkiller)
• Digitalis


  Foxglove (treats heart conditions)
• Penicillin


  Penicillium notatum mould (kills bacteria)
• Placebo


  Fake/dummy drug that does not contain the active ingredient. When you have taken a placebo, your brain will believe it should be getting better as you have taken medicine.
• Medical testing Stage 1


  - Pre clinical

  - 0-3 years

  - Testing on human cells and live animals (mice)

  - Testing to see if drug works (efficiency)
• Medical testing Stage 2


  - Clinical trial on healthy humans (around 3 years)

  - Testing to see how severe side effects are