Communicable diseases, disease prevention and immune system

• Define the terms "communicable disease" and "pathogen"

  Communicable disease - diseases that can be passed from one organism to another of the same or of different speciesPathogen - microorganism that causes disease
• State the 4 different types of pathogen

  BacteriaVirusFungiProtoctists
• Draw, label and annotate a diagram of a generalised virus

  Genetic material with a protein coatMay have enzymes, membrane (stolen from host cell)

  
• Draw and label a series of diagrams to describe the general reproductive cycle of a virus


  Virus binding to surface of cell - receptor on surface on virus and surface protein on host cell bindInject genetic materialCopy genetic material (using host's metabolism)Protein synthesis to make capsid (uses ribosomes of host cell)New viruses constructedNew viruses exit the cell - bursts (or budding)

  
• Describe 5 general ways in which pathogens can damage host tissue, thereby causing harm

  Produce toxins, Inhibit enzymes, burst cells, digest cells, inhibit nervous system
• Identify the host species of, and the type of pathogen causing, the following plant diseases: ring rot, tobacco mosaic virus, potato blight, black sigatoka

  Ring rot - Bacteria - Potatoes, tomatoes, auberginesTobacco mosaic virus - Virus - tobacco plants, tomatoes, peppers, cucumbersPotato blight - Protoctist - potatoes, tomatoesBlack sigatoka - Fungus - Bananas
• Identify the host species of, and the type of pathogen causing, the following animal diseases: tuberculosis, bacterial meningitis, AIDS, Influenza, Malaria, Ring worm, Athlete's foot


  Tuberculosis - Bacteria - Humans, cows, pigs, badgers, deerBacterial meningitis - Bacteria - HumansAIDS - Virus - Humans, non-human primatesInfluenza - Virus - Humans, birds, pigsMalaria - Protoctist - HumansRing worm - Fungus - Cattle, dogs, cats, humansAthlete's foot - Fungus - Humans
• Define the terms "vector", "spore", and "contagious disease"

  Vector - a living or non-living factor that transmits a pathogen from one organism to anotherSpore - a minute, typically one-celled, reproductive unit capable of giving rise to a new individual without sexual fusion, characteristic of lower plants, fungi, and protozoansContagious disease - diseases spread by direct contact
• Describe what is meant by direct transmission and indirect transmission of a pathogen, describe 2 clear examples (mode of transmission and pathogen) of each and describe 2 examples which could be argued to be either direct or indirect transmission.

  Direct - pathogen transferred directly from one organism to anotherDirect contactInoculation (by bite)Indirect - pathogen transferred indirectlyDroplet infectionFomites (inanimate objects e.g. bedding)VectorsUnclear - inoculation (bite direct and needles indirect)
• State the transmission methods for the following plant diseases: ring rot, tobacco mosaic virus, potato blight, black sigatoka


  Ring rot - Direct contact, soil contamination, humans as vectorsTobacco mosaic virus - Direct contact, soil contamination, humans as vectorsPotato blight - spores in water, soil, direct contactBlack sigatoka - spores carried by wind, soil, direct contact
• State the transmission methods for the following animal diseases: tuberculosis, bacterial meningitis, AIDS, Influenza, Malaria, Ring worm, Athlete's foot


  Tuberculosis - Droplet infectionBacterial meningitis - direct contact with bodily fluidsAIDS - Inoculation through break in skinInfluenza - droplet infectionMalaria - Vector - mosquitoesRing worm - Skin to skin contactAthlete's foot - contact with infected skin or fungus in environment
• Describe and explain 7 factors that affect the transmission of communicable diseases in animals

  Overcrowded living and working conditions - More chance for contact + droplet infectionPoor nutrition - weaker immune systemCompromised immune system - weakened defencesPoor disposal of waste - breeding sites for vectors and pathogens contaminating water suppliesClimate change - Vectors spreading - mosquitoes can spread over larger areaCulture and infrastructure - traditional 'medicine', FGM, Lack of clean water, traditional burials, roads, fast diagnostics, researchSocioeconomic factors - lack of trained health professionals, Insufficient public warning/advice/education on prevention
• Describe and explain 6 factors that affect the transmission of communicable diseases in plants

  Planting crop varieties that are susceptible to disease - larger population of pathogen able to infect less susceptible varietiesOvercrowded growing - increases likelihood of contact, increased humidity due to lack of air flow causes increased fungal growthPoor mineral nutrition - reduces resistanceDamp, warm conditions, increase survival and spread of pathogensClimate change - increased rainfall - humidity, animal vectors move to new areasMonoculture practices - lack of variation - all susceptible to disease so spreads easilyPlant cloning practices - lack of variation - if one susceptible, all susceptible
• State 3 examples of barriers to pathogens in plants

  Waxy cuticle, cell wall (cellulose), bark
• Describe the major difference between plants' response to pathogens as compared to animals' response to pathogens, and explain why this is a possible successful strategy for plants.

  Not specific - aims to destroy pathogen or close off infected area to prevent spreadPlants able to lose parts of themselves and survive
• Describe ways in which a plant cell can detect the presence of a pathogen

  Detect chemicals on surface of pathogensDetect break down products of cell wall - beta glucoseCells have receptors on plasma membranes - once activated send chemical signals to nucleus to switch on defence genes. Chemicals also sent to other cells via plasmodesmata to initiate defence genes in other cells in preparation for incoming attack.
• Name two molecules produced by plants to limit the spread of the pathogen

  LigninCallose
• Describe the structure of callose

  Poly saccharide of beta glucose but with 1-3 and 1-6 glycosidic bonds so a different shape to cellulose
• Describe 4 ways callose is used to limit the spread of a pathogen

  Deposited under cell wall between wall and plasma membrane - pathogen's cellulose digesting enzymes will not fit so they cannot digest itProduction continues after end of infection - investing in defence.Seal off sieve plates in phloem to infected area to stop spreadFills plasmodesmata between infected cells and neighbours to stop spread
• List 6 different types of plant chemical defences, and for each describe their role and give examples

  Insect repellents - pine resinInsecticides - caffeine, nicotineAntibacterial - phenolsAntifungal - chitinasesAnti-oomycetes (anti-protoctists) glucanasesGeneral toxins - cyanide
• Define the term "non-specific defences"

  Not targeted - work against all pathogens in the same way
• State 4 barriers the human body has to minimise the entry of pathogens into our cells

  Skin, Mucous membranes, Stomach acid, Blood clotting
• Explain how the skin acts as an effective barrier to the entry of pathogens

  Sheds off - loses pathogens as wellDead cells in surface layer - cannot be hosts for pathogens esp. virusesProduces sebum - inhibits pathogen growthSkin flora - bacteria that compete for space and nutrients
• Explain how mucous membranes act as an effective barrier to the entry of pathogens

  Mucus traps pathogens Cilia move mucus out/swallowMucus has lysosyme - digestive enzyme breaks down bacterial and fungal cell walls Mucus has phagocytes
• Name 4 expulsive reflexes and explain their value for protection against pathogens

  Coughing, sneezing, vomiting, diarrhoeaExpel mucus and contents of gut including any pathogens
• Draw a flow chart to show the process of blood clotting

  Tissue is damagedPlatelets are activated by damaged tissuePlatelets release the enzyme thromboplastin (they also release serotonin which makes smooth muscle in walls of blood vessels contract causing them to narrow and reduce blood loss)In the presence of calcium ions (and vitamin K) thromboplastin catalyses the conversion of prothrombin into thrombinThrombin, an enzyme, catalyses the conversion of fibrinogen (a soluble globular protein) into fibrin (an insoluble fibrous protein)Fibrin molecules form a meshThe fibrin mesh traps platelets and red blood cells to form a clotThe clot dries out to form a hard tough scabThe clot and scab minimise blood loss and minimise entry of pathogens directly into tissues or the blood through broken skin

  
• Explain the importance of blood clotting and the release of serotonin by platelets

  The clot and scab minimise blood loss and minimise entry of pathogens directly into tissues or the blood through broken skinPlatelets release serotonin which makes smooth muscle in walls of blood vessels contract causing them to narrow and reduce blood loss
• Describe the processes involved in the inflammatory response and explain their value for protection against pathogens

  Damaged tissue/pathogens detected by mast cells - release histamine and cytokinesRed - dilation of blood vessels, increased blood flowSwollen - gaps in capillaries widen - 'leakier'Pain - Sensitising nerve endings in skin - makes body protect already damaged areasHot - due to greater blood flow - reduces reproduction of pathogensPus - tissue fluid containing many dead WBC - attracted to the region by cytokines, increased blood flow and able to get out of leaky capillaries
• Describe how fever is initiated in response to invasion by pathogens and explain its value for protection against pathogens

  Cytokines make hypothalomus maintain a high body tempSpecific immune response works faster at higher tempPathogens optimum temp is normal body temp s fever inhibits reproduction
• Define the term "phagocyte" and state two examples of phagocytic cells


  Specialised white blood cells that engulf and destroy pathogensNeutrophils and macrophages
• Describe the stages in phagocytosis

  Phagocyte is attracted to pathogens by chemicals the pathogen producesPhagocyte recognises the pathogen as 'non-self' and binds to itPhagocyte engulfs the pathogen (endocytosis) to form a phagosomeLysosomes move towards the phagosome and the two combine to form a phagolysosomeInside the phagolysosome hydrolytic enzymes such as lysozyme digest the pathogenThe molecules produced from the digestion of the pathogen are absorbed by the phagocyteAntigens from the pathogen combine with major hisocompatibility complex (MHC) glycoproteins in the cytoplasmThe MHC/antigen complexes are moved to the phagocyte's cell surface membrane and are displayedThe phagocyte is now an antigen-presenting cell and can activate the specific immune response
• Define the term "antigen presenting cell"

  a cell that displays foreign antigens complexed with major histocompatibility complexes (MHCs) on their surfaces
• Describe the role of cytokines in the non-specific defences

  Phagocytes that have digested a pathogen release cytokines which signal to other phagocytes to move to the area.Cytokines also encourage the inflammatory response.
• Describe the role of opsonins in phagocytosis

  Opsonins are chemicals that bind to pathogens, tagging them, and are recognised by phagocytes so that they engulf and destroy them.
• Define the term "antigen" and differentiate between "self" and "non-self" antigens

  Antigen - identifying chemical on the surface of a cell that triggers an immune responseCells of own body have self antigens - immune system will not target theseNon-self antigens are recognised and trigger a response
• Define the terms "antibody", "antigen-antibody complex", "lymphocyte" and "specific immune response"

  Antibody - y shaped glycoproteins made by B cells of the immune system in response to non-self antigensAntigen-antibody complex - The complex formed when an antibody binds to an antigenLymphocyte - WBCs that make up the specific immune systemSpecific immune response - Targets specific pathogen due to specific antigen - creates memory cells
• Draw, label and annotate a diagram of an antibody

  
• Describe and explain 4 ways in which antibodies defend the body

  Opsonins - tag pathogens for effective phagocytosisNeutralise pathogens - the binding of antibodies block the function of molecules on the surface of pathogens e.g. those required for the pathogen to bind to a host cellAgglutinins - cause pathogens to clump together - reduces the spread of the pathogen and phagocytes can engulf many pathogens a the same timeAnti-toxins - antibodies bind to toxins to make them harmless
• Explain why B lymphocytes are called "B" whereas T lymphocytes are called "T"

  T mature in the Thymus glandB mature in the Bone marrow
• Name the 4 main types of T lymphocytes and describe their roles

  T helper cells - CD4 receptors on surface bind to antigens on APCs. Produce interleukins that stimulate the activity of B cellsT killer cells - destroy pathogens with 'the' antigen - produce perforin - makes holes in membraneT memory cells - live a long time - immunological memory. Divide rapidly to produce T killer cells on contact with antigenT regulator cells - suppress the immune system - control and regulate. Stop response once pathogen eliminated, prevent autoimmune response