infection and response

• what is a pathogen?

  Microorganisms which cause infectious diseases
• What are viruses?

  microorganisms which reproduce rapidly in body cells and cause damage to the cells
• Describe bacteria


  Pathogen , small living cells that either damage cells directly or by producing toxins, can reproduce rapidly in the appropriate conditions: warm, moist areas with a good supply of oxygen,  toxins released by bacteria can damage cells and tissues, making us feel ill
• What are fungi?


  Single celled organisms that have a body made up of hyphae which are able to grow and penetrate tissues , the hyphae produce spores that can spread to other plants and animals
• What are protists?


  Single celled eukaryotic organisms, they damage tissues which make us feel ill
• How are protists transferred?

  By vectors
• What are the ways that infectious disease can spread?

  Direct contact , air droplets, water , vectors
• How can you reduce the spread of infectious disease?

  Hygiene, vaccination, isolation, protecting against vectors
• Tobacco mosaic virus 


  It is transmitted by direct contact. It infects the chloroplasts of plant leaves and changes their colour from green to yellow or white in a mosaic pattern. It can also make leaves crinkled or curled up. This reduces the plant's ability to photosynthesise and grow properly, which can reduce farmers' crop yields
• HIV


  Spread by sexual contact or exchange of bodily fluids

  Flu like symptoms at first and then if untreated attacks the immune system, the virus enters the lymph nodes and attacks the body's immune cells. AIDS can be caused as a result
• measles


  Caused by a virus , spread by breathing in air droplets from sneezes and coughs , symptoms are fever and a red rash
• How do HIV and AIDS differ?

  HIV is a virus that attacks the immune system, while AIDS is a condition that develops as a result of untreated HIV infection due to the immune system being damaged
• Salmonella 


  Bacterial disease , type of food poisoning , if food has not been cooed properly or has been prepared unhygienically we may ingest salmonella bacteria which release toxins causing fever , stomach pain , vomiting and diarrhoea
• Gonorrhea

  symptoms: thick yellow or green discharge from the vagina or penis and pain when urinating

  the use of barrier contraception can be used to stop the bacteria from being passed on

  sexually transmitted disease caused by bacteria - spread by sexual contact
• rose black spot


  fungal disease, spread when spores are carried by the wind or water from plant to plant , causes purple or black spots on the leaves of rose plants. Eventually the leaves discolour and fall off which makes it harder for the plant to photosynthesise and plant growth slows
• how can rose black spot be treated?

  removing and destroying discolored leaves and using fungicides to treat affected plants
• malaria


  carried by mosquito (vector) : passed onto person when they are bitten by the mosquito , it transfers the infection into the bloodstream. Malaria leads to recurring and severe fevers which can cause death
• how does stomach acid defend the body against disease?

  glands in the stomach wall produce hydrochloric acid which destroys any pathogens which enter the stomach
• how do tears help to defend against disease?

  they contain enzymes which destroy pathogens which make contact with the eye
• how does mucus help defend against disease?

  produced in goblet cells in the respiratory system and traps particles and bacteria entering airways, cilia sweep mucus along
• how does the skin help to defend against infection?

  The skin covers almost all parts of your body to prevent infection from pathogens , creates a barrier which pathogens cannot pass through. Sebaceous gland under the skin produces sebum which kills bacteria and fungi
• how do phagocytes help to defend against disease?

  phagocytosis:

  • A white blood cell finds the pathogen and engulfs it by changing shape.
  • The white blood cell ingests (absorbs) and digests the pathogen, destroying it.
• how do lymphocytes help to defend the body against disease?

  produce antibodies which attach to the antigen molecules on the pathogen + they produce antitoxins which neutralise the effects of bacterial toxins
• what affect does magnesium deficiency have on plants?

  magnesium is required for the production of chlorophyll , causes chlorosis as the plant cannot photosynthesise well so cannot produce the glucose needed for healthy growth - plant leaves are yellow
• what does nitrate deficiency cause?

  Stunted growth because they are needed for the production and synthesis of proteins and without proteins plants cannot grow
• chemical plant defences

  Poisons are produced by many plants, including foxglove and deadly nightshade, to deter (put off) herbivores.

  Antibacterial chemicals are produced by some plants, such as mint, garlic and witch hazel. They work like antibiotics to stop populations of bacteria from growing.
• mechanical plant defences

  thorns/hairs stop animals from eating the plants

  leaves that close up rapidly when touched decrease the surface area available to herbivores may also dislodge smaller herbivores already on the plant

  some plants use micricry to trick animals
• physical plant defences

  Bark is made of dead cells that acts as a barrier of protection for the stem against pathogens and pests (like aphids).

  Waxy cuticle is a barrier on the surface of leaves and stems to stop pathogens invading leaf tissue.

  Cell walls, which are made of cellulose, are a physical barrier to stop pathogens entering cells.
• methods to identify plant disease

  Take an infected plant to a laboratory to identify the pathogen , refer to a gardening manual or website or using testing kits which contain monoclonal antibodies
• how are monoclonal antibodies made?

  a mouse is injected with antigens from specific pathogen , the mouse produces lymphocytes. These are fused with myeloma cells to produce hybridoma cells which produce rapidly - the monoclonal antibodies are extracted and purified
• what can monoclonal antibodies be used for?

  pregnancy test, treating disease
• where is aspirin found?

  Willow bark
• where did digitalis originate from?


  foxgloves