Biology topic 3

• pathogens are microorganisms that enter the body and cause communicable disease
• pathogens can affect plants and animals
• bacteria

  1. small cells that rapidly reproduce
  2. make you feel ill as they release toxins that damage cells and tissue
• viruses

  1. not cells
  2. 1/100 size of bacteria
  3. reproduce rapidly - live in cells and replicated themselves using cells machinery to produce copies
  4. cells burst which releases new viruses which makes you feel ill
• protists

  1. some single celled
  2. some parasites with body made of hyphae, they grow and penetrate human skin and plant surfaces which causes disease
  3. hyphae produces spores which spreads to other plants
• how do diseases spread

  1. direct contact
  2. air
  3. water
• spread of disease by water

  1. drinking or washing in contaminated waters
  2. e.g. cholera was a bacterial infections cause by drinking water with faeces in it
• spread of disease by air

  1. airborne pathogens are carried in air droplets from coughing and sneezing
  2. e.g. corona virus
• spread of disease by contact

  1. touching contaminated surfaces
  2. e.g. athletes food is a fungal disease which causes itchin
• measles

  1. spread by infected droplets from a person coughing
  2. fever and red skin / rash
  3. can be treated with vaccine
  4. can lead to pneumonia or brain infection
• HIV

  1. exchange of body fluids
  2. flu like symptoms that can be controlled by antiretroviral drugs
  3. attacks immune system
• tobacco mosaic virus

  1. creates mosaic pattern on plant leaf and causes decolourisation
  2. reduces photosynthesis and stunts growth
• rose black spots

  1. fungal
  2. causes purple and black on leaves that turn yellow and drop off
  3. reduces photosynthesis
  4. spread by water and wind
  5. treated by fungicide or stripping infected leaves from plant
• malaria

  1. caused by protists
  2. a mosquito is a vector which feeds on an infected plant and picks up malaria protist
  3. feeds on other animas it passes on the infected protists into the animals blood vessels making them become infected
  4. causes fever
  5. mosquitoes can be avoided with insecticides
• salmonella

  1. contaminated food
  2. bacteria causes food poisoning
  3. diarrhoea, stomach cramps, vomiting fever
  4. bacteria produces toxins which creates symptoms
• gonorrhoea

  1. STD
  2. caused by bacteria
  3. originally treated with penicillin but now become immune
  4. pain when urinating and green discharge
• preventing diseases

  1. hygiene - wash hands and food, clean surfaces dont sneeze on food
  2. vaccines - against communicable diseases so cant develop an infection
  3. destroying vectors - stops spreads - an destroy habitats or kill them with insecticides
  4. isolation - prevent spreading
• bodies defence system

  1. skin is a barrier to pathogens and secretes antimicrobial substances which kill pathogens
  2. hair and mucus in nose trap particles with pathogens
  3. trachea and bronchi secrete mucus which traps pathogens, and contains cilia which is a half hair like structure which wafts mucus back up to the throat
• bodies line of attack

  1. consuming
  2. antibodies
  3. antitoxins
• consuming pathogens

  white blood cells engulf foreign cells and digest them this is called phagocytosis
• creating antibodies

  1. invading pathogen has a unique molecule on the surface called an antigen
  2. when some white blood cells come across foreign antigen they start to produce proteins called antibodies which lock onto invading cells so they can be found and destroyed by other white blood cells
  3. antibodies are produced rapidly and go around the body detecting any of the same bacteria or virus
  4. if attacked with the same pathogen again the body can quickly produce antibodies and kill invading pathogen
• creating antitoxins

  counteract toxins produced by invading pathogen
• a vaccine is an injection of a small amount of the dead or inactive pathogen which carry antigens meaning the body produces antibodies
• what are the pros of vaccines

  1. control communicable diseases
  2. can prevent outbreak of disease
• what are the cons of vaccines

  1. can have negative side effects
  2. dont always work
• painkillers only relieve pain they dont destroy disease
• antibiotics kill or prevent the bacteria that's causing the problem without harming body cells
• antibiotics dont destroy viruses
• viruses reproduce using their own body cells so they are difficult to treat without harming your own cells
• bacteria can mutate and become resistant to anitbiotics
• doctors avoid bacteria becoming immune to antibiotics by not overprescribing
• plants produce a variety of chemicals that defend against pests and pathogens
• drug testing

  1. preclinical trial - testing on human cells and tissues
  2. testing on 2 live animals - test for efficiency and optimum dosage
  3. test on human volunteers - first with healthy people at low dosage then increase dosage if no side effects
  4. use the placebo effect for best results
• plants need mineral ions from soil or they will get deficiency issues. they need nitrate for making proteins which is used for growth if not the plant will have stunted growth. plants need magnesium ions as they produce chlorophyll which is needed for photosynthesis if not the plant will suffer from chlorosis and yellow leaves
• signs of diseases on plants

  1. decoloured
  2. stunted growth
  3. weird leaf pattern
  4. rot
  5. lumps
  6. malformed
• plants physical defence system against disease

  1. waxy cuticles which act as a barrier to pathogens
  2. cell walls made from cellulose
  3. layer of dead cells around stem which acts as barrier
• plants chemical defence system against disease

  1. antibacterial chemicals which kills bacteria
• plants mechanical defence system against disease

  1. thorns stop animals eating them
  2. leaves that curl so unwanted things drop off
  3. mimic other organisms
• monoclonal antibodies are produced by clones of the same white blood cell so they are all identical and only target 1 antigen
• monoclonal antibodies

  1. lymphocytes dont divide easily
  2. tumour cells divide but dont produce antibodies
  3. fuse lymphocytes and tumour cell together to form hybridomas
  4. hybridoma is cloned to create identical copies of an antibody which are collected and purified