B5: Communicable diseases

• Why do plants need a good supply of nitrate ions?


  To convert sugars into proteins for growth
• Why do plants need a good supply of magnesium ions?


  To produce chlorophyll for photosynthesis
• Name three symptoms of plant disease

  Stunted growth

  Discoloured leaves

  Malformation of stems/leaves
• What are three ways that plant disease can be identified?

  Comparing it to images in a gardening website or manual

  Testing in a lab

  Monoclonal antibody test kits
• Name 3 physical defence responses in plants

  Cellulose cell walls

  Waxy cuticle layer on leaves

  Outer layer of bark on trees
• Name 2 chemical defence responses in plants

  Antibacterial chemicals

  Releasing poison
• Name 3 mechanical defence responses in plants

  Thorns or hairs

  Leaves curling on contact

  Mimicry
• Monoclonal antibodies

  Antibodies that are clones of a parent cell and are specific to one type of antigen
• How are monoclonal antibodies produced?

  First, an antigen is injected into an animal

  Next, B-Lymphocytes producing complementary antibodies are extracted

  Then, the B-Lymphocytes fuse with myeloma to form Hybridoma cells

  The Hybridoma cells divide and make antibodies

  The monoclonal antibodies are then collected and purified
• What are monoclonal antibodies used for?

  •Pregnancy tests

  •Treating cancer

  •Detecting pathogens
• Myeloma cells


  A type of tumour cell
• What do pregnancy tests detect?

  The hormone, hCG, in urine
• Why are monoclonal antibodies used to test for pathogens?

  •Accurate

  •Quick

  •Specific to a particular antigen
• Why are cancer treatments using monoclonal antibodies better than traditional treatments?

  Monoclonal antibodies only target the cancer cells, whereas treatments like radiotherapy and chemotherapy can damage healthy cells
• Communicable disease

  A disease caused by a pathogen that can be transmitted between animals or plants
• Pathogen


  Disease-causing microorganism
• How do bacteria cause disease?

  They divide rapidly in the body, kill cells and produce toxins
• How do viruses cause disease?

  They reproduce in body cells, causing damage to them
• How are pathogens spread?

  Air

  Water

  Contact
• How can the spread of pathogens be reduced?

  Hygiene (e.g. washing hands)

  Reducing contact with infected people

  Vaccines

  Removing vectors (e.g. pesticides)
• What is measles?

  A viral disease that can cause blindness, brain damage, fever and rash

  It is spread through the air
• What is HIV?

  A virus that damages the immune system, and is spread by sexual contact or exchange of body fluids (e.g. blood)
• How can HIV be prevented?

  Safe sex (using condoms)

  Not sharing needles

  HIV-positive mothers bottle-feeding
• What is Tobacco Mosaic Virus (TMV)?

  A plant pathogen which causes discolouration in leaves and damaged cells

  It reduces photosynthesis rate, and therefore crop yield

  It is spread by contact or vectors
• What is salmonella?

  A type of bacteria found in raw meat or egg.

  It can cause fever, cramping or vomiting and can be fatal

  It is prevented by vaccinating animals, disinfecting surfaces and thoroughly cooking meat
• How does the skin prevent pathogens from entering the body?

  It acts as a barrier

  Scab is formed after the skin is cut
• How does the respiratory system prevent pathogens from infecting the body?

  Nose has hair and mucus to trap pathogens

  Trachea and bronchi have mucus to trap pathogens
• How does the stomach prevent pathogens from infecting the body?

  Hydrochloric acid kills pathogens
• How do white blood cells protect us against disease?

  Phagocytes ingest and destroy pathogens

  They also produce antibodies, which complement and bind to a specific antigen on a pathogen, causing them to clump together to be destroyed easily