b3

• B3 What is the first stage of testing of a new medicinal drug?

  Testing on human cells and tissues (in vitro)
• B3 How does the stomach help to defend the body against pathogens?

  It produces hydrochloric acid that kills pathogens
• B3 What is a pathogen?

  A pathogen is a microorganism that causes disease
• B3 Which drug was developed by Alexander Fleming?

  Penicillin
• B3 Gonorrhoea is a disease caused by...

  a bacterium
• B3 What can successfully control an HIV infection?

  antiretroviral drugs
• B3 How does the measles virus spread?

  Measles is spread by inhalation of droplets from sneezes and coughs
• B3 Explain why the tobacco mosaic virus (TMV) affects the growth of plants

  TMV causes discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis
• B3 How does malaria spread?Explain how mosquito nets help to prevent the spread of malaria.

  Mosquitos are the vector that carries plasmodium (the protist that causes malaria) and mosquitos infect humans with the protist through biting
• B3 Explain how a lack of nitrate affects a plant's growth.

  Nitrates are required to make amino acids for protein synthesis
• B3 What is a placebo?

  A substance that looks like a test drug, but does not do anything
• B3 Which disease in humans can be partly controlled by vaccinating poultry against the pathogen?

  Salmonella food poisoning
• B3 What is the main difference between an antibiotic and a painkiller?

  Antibiotics kills bacterial pathogens, painkillers treat symptoms but do not kill the pathogens
• B3 Name a disesase that young children are usually vaccinated against

  Any of the following: measles, mumps, Rubella, diphtheria, polio, meningitis C, whooping cough
• B3 What is phagocytosis?

  Phagocytosis is the process by which white blood cells (phagocytes) engulf and digest pathogens
• B3 Name a fungal disease that affects plants

  Rose black spot
• B3 How do viruses make you feel ill?

  Viruses replicate inside cells and cause cell damage
• B3 How does the nose help to defend the body against disease?

  The nose contains hairs and mucous which trap particles that could contain pathogens
• B3 Explain how vaccination can protect against a disease

  Vaccines contain dead or weakened pathogens that carry antigens. The antigens in the vaccine activate white blood cells to produce antibodies and memory cells. If the same type of pathogen enters the body again, memory cells rapidly produce antibodies to kill the pathogen
• B3 What is penicillin?

  An antibiotic
• B3 What is herd immunity?

  When the spread of pathogens can be reduced by immunising a large proportion of the population
• B3 What are antibodies?

  proteins produced by white blood cells that match the shape of antigens on a specific pathogen and help destroy them
• B3 Name a disease caused by a protist

  Malaria
• B3 From where did aspirin originate?

  willow
• B3 What is an antigen?

  Antigens are molecules on the surface of pathogens that are recognised by the immune system
• B3 What is a double-blind trial and why is it used in clinical trials?

  In a double-blind trial, neither the patient nor the doctor know who is having the test drug or the placebo. This is used to prevent bias.
• B3 Describe how monoclonal antibodies can be used to treat cancer.

  Monoclonal antibodies can be made against antigens on cancer cells. The monoclonal antibody is bound to a radioactive substance, a toxic drug, or a chemical that stops cells growing and dividing, it will deliver the substance to the cancer cells without harming other cells in the body.
• B3 How can you prepare an uncontaminated bacterial culture?

  Use sterilised Petri dishes and sterilised culture media; sterilise the innoculating loop with a flame; losely secure the Petri dish lid with tape and store upside down
• B3 Why should cultures be incubated at 25oC in school or college labs?

  harmful pathogens are unlikely to grow at 25oC
• B3 What are monoclonal antibodies?

  Monoclonal antibodies are antibodies that are produced from a single clone of white blood cells
• B3 How are monoclonal antibodies produced?

  Mouse lymphocytes are stimulated to produce a particular antibody. The lymphocytes are combined with a tumour cell to make a hybridoma cell, which can both divide endlessly and produce antibodies. Single hybridoma cell can be cloned to produce identical cells making identical antibodies.