Biology Y9 B2-B2.8

Subdecks (1)

Cards (88)

  • Pathogens
    Organisms that cause disease
  • Four major types of pathogen
    • Bacteria
    • Fungi
    • Protozoa
    • Virus
  • How pathogens cause illness

    • Toxins
    • Reproduction
    • Immune response
  • How pathogens are spread
    • Direct contact
    • Indirect contact
    • Food and water
    • Airborne droplets
    • Insect bites
  • Natural defences
    • Physical and chemical barriers (First Line)
    • Non-specific defences (Second Line)
    • Pathogen-specific defences (Third Line)
  • Tuberculosis (TB)

    Infectious disease caused by the bacteria Mycobacterium tuberculosis, attacking the respiratory system
  • Infectious diseases usually decline as living conditions and standards of healthcare improve
  • Painkillers can relieve the symptoms of an infection but do not kill the pathogen
  • Invasion of pathogen
    1. Pathogen enters body
    2. Immune system mounts attack
    3. Pathogen reproduces and makes toxins
  • Lymphocytes
    Type of white blood cell found in blood or lymph nodes, made by bone marrow, including T-lymphocytes and B-lymphocytes
  • Antibodies
    • Special Y-shaped proteins produced by B-lymphocytes in response to antigens, binding to and labelling pathogens for destruction
  • Delayed response

    It takes a few days to produce enough antibodies to destroy the pathogen
  • Active immunity
    Memory cells remain after pathogen is destroyed, recognizing the pathogen if it re-infects and mounting a quicker, more effective immune response
  • Vaccines
    Contain a small amount of dead or weakened pathogen particles, stimulating antibody and memory cell production without making the person ill
  • MMR vaccination rates used to be high, but fell following a media scare story about a speculative link between MMR and autism
  • Independent expert scientists re-examined the original research and found no evidence of a link between the MMR vaccine and autism
  • If 95% of children had the MMR jab the diseases could be wiped out in the UK, this is called herd immunity
  • Antibiotics
    Drugs used to treat bacterial infections, either bactericidal (kill bacterial cells) or bacteriostatic (slow bacterial growth/reproduction)
  • Antibiotics are effective against prokaryotic cells but generally leave human cells unharmed
  • Antibiotic resistance
    Bacteria with resistance to an antibiotic have an advantage and can survive and reproduce, giving rise to a population of resistant bacteria
  • Antibiotic resistance is evolving faster than the development of new antibiotics
  • Mutations of bacterial pathogens produce new strains, some of which may become immune to antibiotics
  • The evolution of antibiotic resistance is an example of natural selection
  • Methicillin-resistant Staphylococcus aureus (MRSA) is becoming common in hospitals and can cause life-threatening infections
  • Methods to prevent and control antibiotic resistance
    • Antibiotics should only be prescribed when needed
    • Patients should finish the complete course of antibiotics
    • Introduction of infection control in hospitals
  • Pathogen
    A microorganism that can cause a disease
  • Pathogens can be passed on from one person to another. Diseases caused by pathogens are known to be COMMUNICABLE DISEASES
  • Types of pathogens

    • Viruses
    • Bacteria
    • Fungi
    • Protists
  • Viruses
    • Not considered as living organisms as they cannot survive outside a host
  • Bacteria
    Prokaryotes that do not contain mitochondria and produce toxins
  • Fungi
    Can be single or multicellular, cell wall made from chitin, have thread-like structures called hyphae
  • Single cellular fungus

    • YEAST
  • Multicellular fungus
    • MUSHROOM
  • Protists
    Single celled eukaryotic organisms, may be parasitic and can cause malaria
  • Viruses reproduce rapidly inside host cells until they burst open
  • Viruses are too small in size to observe under the light microscope. To see a virus we would need a special microscope called an Electron Microscope
  • We do not have any slides of viruses under the microscope
  • Bacteria and protists can be observed under the light microscope
  • Pathogens can cause communicable diseases
  • Not all diseases are infectious