SB5 + SB6

Cards (165)

  • Viruses are not cells; they are a protein coat around a strand of genetic material.
  • Viruses need to infect a living cell (host) to reproduce.
  • Specific viruses will only affect specific cells.
  • Virus Lifecycle
    1. Infects new host cell
    2. Reproduces by lytic pathway
    3. Reproduces by lysogenic pathway
  • Lytic pathway
    1. Virus attaches to specific cell
    2. Injects genetic material
    3. Uses host proteins and enzymes
    4. Assembles viral components
    5. Host cell splits and releases new viruses
  • Lysogenic pathway
    1. Injected genetic material incorporated into host genome
    2. Viral genetic material replicated with host DNA
    3. Virus remains dormant
    4. Trigger causes viral material to enter lytic pathway
  • STI’s are spread through sexual contact.
  • STI examples
    • Chlamydia
    • HIV/AIDS
  • Chlamydia
    A kind of bacterium but behaves like a virus because it can only reproduce inside host cells
  • Chlamydia doesn’t cause symptoms but can result in infertility.
  • The spread of Chlamydia can be reduced by wearing a condom or being treated for the infection.
  • HIV
    Human immunodeficiency virus kills white blood cells important in immune response
  • HIV eventually leads to AIDS (Acquired immune deficiency syndrome).
  • The infected person’s immune system deteriorates and eventually fails, making them vulnerable to infections by other pathogens.
  • HIV is spread by infected bodily fluids.
  • One of the main ways to prevent the spread of HIV is to use a condom.
  • Drug users should avoid sharing needles to reduce the spread of HIV.
  • Plants have physical defences against pathogens and pests.
  • Waxy cuticle
    Provides a barrier stopping pathogens entering or damaging leaves and stems
  • Waxy cuticle may also stop water collecting on the leaf, reducing the risk of infection from pathogens transferred between plants and water.
  • Plant cells are surrounded by cell walls made from cellulose, forming a physical barrier against pathogens.
  • Chemical defences in plants
    Produce chemicals called “antiseptics” which kill bacteria and fungal pathogens<|>Produce chemicals to stop pests feeding on their leaves
  • Some plant chemicals are used as drugs by humans.
  • Plant-derived drugs

    • Quinine
    • Aspirin
  • Quinine
    Comes from bark and is used to treat malaria
  • Aspirin
    Found in bark and leaves of willow trees and is used to treat pain and fever
  • Plant pathologists recognise symptoms of diseases in the field, such as abnormal growth or yellow leaves.
  • Pathogens spread in different ways, allowing pathologists to analyse the distribution of diseased plants to identify the kind of pathogen involved.
  • Lab testing will give accurate identification of the pathogens.
  • Antigens
    Unique molecules on the surface of pathogens
  • Antigens from a particular pathogen will be present in an infected plant and can be detected using a sample of tissue.
  • The detection of an antigen allows that pathogen to be identified and the disease diagnosed.
  • If a plant is infected with a pathogen, the pathogen’s DNA will be in the plant's tissues.
  • Scientists detect pathogen DNA using techniques on the smallest amount of pathogen DNA from the tissue.
  • Physical and chemical barriers stop pathogens entering the human body.
  • Physical barriers
    The skin acts as a barrier to pathogens<|>Hairs and mucus in the nose trap particles<|>Cells in trachea and bronchi produce mucus and have cilia
  • If the skin gets damaged, the blood clots quickly sealing any cuts to keep micro-organisms out.
  • Stomach acid kills most pathogens that are swallowed.
  • The eyes produce lysozyme (in tears) which kills bacteria on the surface of the eye.
  • If a pathogen makes it into your body, your immune system kicks in to destroy them.