B6.2

• viruses have to invade to survive
• viruses are non-living
• viruses insert their own DNA into the host cell and duplicate itself until the cell bursts
• HIV attacks the white blood cells, lowering their numbers

  .

  when their number is too low the immune system is weak, and the individual is said to have AIDS

  .

  secordary infections (like TB) can take control of the host, the body is unable to fight leading to death.
• a disease is is a condition that is caused by any part of the body not functioning properly
• communicable disease

  a disease which can be transmitted through organisms
• non-communicable disease

  a disease which cannot be spread between organisms
• pathogens

  pathogens are micro-organisms that cause disease when existing on/in an organism
• types of pathogens

  -fungi

  -bacteria

  -viruses

  -protozoa
• protazoa are unicelluar organisms that are eukaryotes and have nuclei

  .

  they can either be free-living or parasites

  .

  they use a vector to enter the host
• how can a fungal infection be treated?

  antifungal medication
• how can a bacterial infection be treated?

  with antibiotics
• how can a protozoa infection be treated?

  antiparasitic medication
• how can a virus be treated?

  antiviral medication
• examples of virus

  -HIV

  -covid
• examples of protozoa


  -malaria
• examples of bacteria infections

  -food poisoning

  -TB
• examples of fungal infections


  -athletes foot
• how is a fungal infection transmitted?

  direct and indirect contact
• how is a bacterial infection transmitted?

  sexual contact
• how is a protozoa infection transmitted?

  insect bites
• how is a virus transmitted?

  direct and in-direct contact
• viral replication

  virus infects a host

  .

  virus attaches to the surface membrane of a cell using its surface proteins

  .

  it inserts virus DNA to hosts DNA

  .

  host cell makes copies of the virus

  .

  host cell bursts (lysis) releasing more viruses

  .

  the viruses infect more cells
• transmission in plants

  -direct contact

  -vectors
• transmission in animals

  -cuts in skin

  -digestive system
• scab formation

  skin is cut

  .

  platelets change the protein fibrinogen to form a mesh

  .

  red blood cells are trapped in the mesh forming a blood clot

  .

  clot hardens and dries
• what is a non-specific defence?

  this is the 1st line of defence that try to prevent infections

  .

  some examples:

  -skin

  -ears
• secondary immune response

  large release of antibodies to fight pathogens off before it makes you ill
• active immunity

  white blood cells learn to make the right antibodies for the antigens of pathogens
• passive immunity

  recieving antibodies from a vaccine that gives temporary immunity
• antibodies

  proteins that bind to antigens on the surface of micro-organisms
• herd immunity


  when enough of the population is vaccinated, the disease is unable to spread to unvaccinated people
• what does a tear-duct do to help prevent infections?

  tear-ducts contain lysozymes that destroy bacteria
• what do our nasal hairs do to help prevent infections?



  they keep out dust and larger micro-organisms
• what does sebum do to help prevent infections?


  sebum is produced from the sweat glands, which helps to kill micro-organisms
• primary reponse


  1st release of antibodies to fight off initial infection
• memory cells


  the body remembers how to fight a specific pathogen
• examples of non-communicable diseases


  -cardiovascular disease

  -cancer

  -diabetes
• examples of communicable diseases


  -malaria

  -TB
• phagocytes absorb pathogens using enzymes to break them down