b3

• Viruses reproduce rapidly by inserting genetic material into host cells and creating a new protein capsule to build new viral particles. Once many copies have been made the host cell may burst open releasing the viral particles which can go on to infect other cells.
• Bacteria enters the host organism, multiplies by division and produces toxins which directly damage cells and tissues
• Viruses are non-living organisms as they don’t contain DNA and can’t reproduce.
• HIV is a viral infection transmitted through the exchange of bodily fluids, primarily through sexual contact
• Symptoms of HIV include fever, tiredness, and aches
• Currently, there is no cure for HIV, but it can be prevented by using condoms or taking medication to prevent the progression of HIV to AIDS
• HIV weakens the body's immune system, leading to the development of AIDS where the immune system is unable to fight off infections
• HIV and AIDS do not directly kill the infected person; instead, the weakened immune system makes the person susceptible to other infections that can be fatal
• Measles is a viral disease spread by inhalation of droplets from coughs and sneezes. Measles can be presented by a red skin rash and a fever. Most people recover well from measles, however it can be fatal if complications arise. Most young people are now vaccinated against measles by the MMR vaccine.
• Tobacco mosaic virus infects plants species like tomatoes, cucumbers and peppers. This can be seen as a yellow and white mosaic pattern on the leaves. The pattern is caused due to the virus infecting chloroplasts and therefore reducing the plant’s ability to photosynthesise and grow. This virus can be spread by farmers and naturally. Currently there is no cure for TMV, so the infected plant must be burned.
• Salmonella is a food poisoning spread by bacteria in poultry. It can be spread by ingesting uncooked poultry meat, unhygenic handling and preparation of poultry and contaminated food. Salmonella can present by fever, stomach cramps, vomiting and diarrhoea, and spread to the liver, kidneys and other organs. In the UK poultry are vaccinated against salmonella preventing the spread of this disease.
• Gonorrhoea is a sexually transmitted disease. It is caused by the infection of bacteria via unprotected sexual contact. Gonorrhoea can be identified by having thick yellow/green discharge and pain urinating. It can be treated by antibiotics and prevented by using condoms. If left untreated it can be spread from mother to child during pregnancy.
• Rose black spot is a fungus spread between plants. It caused black spots to form on plant leaves. These spots indicate the infection of chlorophyll, therefore less light is absorbed and the plant cannot photosynthesise causing stunted growth. Rose black spot can be spread by spores carried in the wind or water and can be treat using fungicides and cutting off the infected parts of the plant.
• Physical defences of plants include: tough waxy cuticles on leaves, tough cellulose on cell walls and layers of dead cells around stems that fall off
• chemical defences of plants include: produce poison, release antibiotic.
• Mechanical defences of plants include: thorns, hairs, mimicry, leaves that curl up when touched.
• mimicry is where it changes its features like their colour or shape to look more like a dangerous organism
• a tough waxy cuticle, bark, and cellulose cell wall forms a barrier to stop bacteria from entering the plant
• poison kills or puts the organism in agony so it doesn’t return
• thorns and hairs prevent organisms from touching and eating the plants
• antibiotics kill off bacteria
• Leaves that curl up when touched prevents themselves from being eaten as it decreases its surface area so knocks off insects and moves away from surrounding dangers
• Plants need mineral ions from the soil taken in via active transport.

  Nitrates - proteins for growth, if not stunted growth

  magnesium ions- making chlorophyll for photosynthesis, if not then chlorosis and yellow leaves
• malaria is caused by mosquitoes which are vectors, and the pathogens that the mosquitoes carry are protists. The protist has a life cycle which includes the mosquito.
• Malaria causes episodes of fever and can be fatal
• Ways in which you can prevent against malaria include: mosquito net, mosquito spray that contains DEET, preventative medication, long clothes
• Reducing area of still water and wet grounds reduces the reproduction of mosquitoes
• Malaria is caused by the vector (mosquito) being infected by a protist, which then bites a human and their saliva is transferred into the blood stream, letting the protists travel to the liver where they reproduce, then travel round the whole body, bursting red blood cells.
• The human defence system uses enzymes in saliva, hydrochloric acid in the stomach, cilia hair cells in the nose and trachea, mucus, tears, sweat, ear wax and skin.
• Saliva and tears have antibacterial enzymes. Skin is a barrier. Mucus forms a lining that traps dirt and microbes. Stomach acid has a low pH which kills the microbes. Good gut bacteria out competes the bad gut bacteria.
• Phagocytosis

  • White blood cells organise and control phagocytosis and production of antibodies and production of antitoxins
  • Phagocytes engulf the pathogens and digest them using enzymes
• Production of antibodies

  • lymphocytes produce antibodies and each antibody has a specific shape that is complementary to the antigens on the pathogen.
  • Takes a few days for the antibodies to be made, which is why you feel unwell at first
  • Memory cells stay in the body after the first infection, so they produce specific antibodies for its complementary antigen, so if you get infected again by the same pathogen, antibodies can be made quicker, so causes less infection and damage
• Production of anti toxins

  • pathogens produce substances that act as toxins to make you feel unwell
  • Lymphocytes produces anti toxins to fight against the toxins
  • Anti toxins neutralise the effects of the toxin
• Herd immunity is where most of the population is vaccinated to prevent the spread to those unvaccinated
• Vaccinations

  • Dead or inactive pathogen or antigens of the pathogen are injected into a healthy person which triggers an immune response and memory cells are produced from the immune response for when the actual pathogen infects you
• Active immunity- body creates antibodies for itself by either being exposed to the disease or having a vaccine

  passive immunity- antibodies are given to you from another organism, for example mother to foetus
• Antibiotics

  eg penicillin interferes with bacterial cell wall and causes the bacteria to rupture and die when it tries to grow

  no cell wall to form again
• antibiotic resistance

  • can be developed by bacteria having random mutations in the DNA due to the antibiotic being overused
  • to prevent bacteria from becoming resistant, doctors need to avoid overusing antibiotics and should rotate between antibiotics taken and isolate patient if necessary
• Most drugs are extracted from plants and microorganisms eg aspirin is made from willow bark, but most new drugs are made by chemists in the pharmacy industry
• penicillin was the first antibiotic to be discovered, and the penicillin mould released a chemical which killed the bacteria surrounding it