Biology high markers (B3)

• How vaccination works (4 marks)

  • injecting a dead/inactive form of the pathogen
  • white blood cells will produce specific antibodies
  • memory cells are produced/remain in the body
  • if reinfected your white blood cells can quickly produce the correct antibodies
  • pathogen is destroyed before it has chance to reproduce/cause symptoms
• Explain what testing must be done on the new drug before it can be used to treat any patients (6 marks)

  • pre-clinical testing- tested on cells/tissues/animals
  • checking for toxicity
  • clinical trials- small number of healthy volunteers
  • checking for side effects
  • test on patients
  • checking for efficacy
  • large sample testing
  • double blind trial + placebo
  • no one knows if they have the real drug or the placebo
  • results will be peer reviewed
• Explain why TMV have stunted plant growth (4 marks)

  • less chlorophyll means less photosynthesis
  • less glucose produced
  • less energy for growth
  • glucose is needed for respiration
  • less protein made
  • glucose is needed to make protein
• How viruses spread + multiply (3 marks)

  1. Viruses can pass between humans via the air, contaminated food or water, or by direct contact.
  2. As they can't reproduce themselves, viruses have to enter one of our cells, and then use it to create multiple copies of the virus itself.
  3. Once there are lots of copies, the viruses cause the cell to burst, and then go on to infect neighbouring cells. 
• Stages of phagocytosis (4 marks)

  1. Phagocytosis is carried out by a special type of white blood cell called a phagocyte. 
  2. The first step is for the phagocyte to track down a pathogen, and then bind to it. 
  3. The phagocyte's membrane will then surround the pathogen and engulf it.
  4. Finally, enzymes inside the phagocyte break down the pathogen in order to destroy it.
• Stages of drug development (4 marks)

  1. Stage 1 - Test the drug on human cells and tissues.
  2. Stage 2 - Test the drug on live animals.
  3. Stage 3a - Test the drug on healthy volunteers to find the maximum dosage before side effects occur.
  4. Stage 3b - Test the drug on patients that suffer from the relevant disease, to find the optimum dosage.
• Why is it important for medical trials to be double-blind? (3 markers)

  • To avoid any bias by the patients and/or researchers
  • If patients know they received the drug they may be more likely to report side effects
  • If researchers know who has been given the real drug then they may pay closer attention to those patients