Communicable Diseases Flashcards
name 4 types of pathogen that can cause communicable diseases
bacteria
fungi
protoctista
viruses
how does myobacterium tuberculosis cause disease
triggers inflammatory response by infecting phagocytes in lungs
infected phagocytes sealed in waxy coated tubercles so bacteria remain dormant
first infection has no symptoms
if another factor weakens immune system, bacteria becomes active and destroys lung tissue
how does HIV result in symptoms of AIDS
attachment proteins bind to complementary CD4 receptors on Th cells
HIV replicates inside Th cells killing or damaging them
AIDS develops when there were too few Th cells for immune system to function
individuals cannot destroy other pathogens and suffer from secondary diseases
how does tobacco mosaic virus cause disease
affects plants and transmitted via sap
contains ssRA which is directly transcribed by host cell to assemble new virions
virions enter cells via plasmodesmata then enter xylem and phloem
causes stunted growth
how does the influenza virus cause disease
transmitted via droplet infection
injects viral RNA into ciliated epithelial cells of throat and lungs
viral RNA hijacks cell biochemistry to produce new virions
cell lysis releases virions
what causes malaria
female mosquito acts as vector when it transfers saliva to another organism during feeding
parasite reproduces asexually in red blood cells causing lysis
what causes potato blight
protoctista behaves similarly to a fungus
mainly transmitted via spores
what causes ring rot
bacteria mainly transmitted by planting infecting seeds
describe 3 fungal infections
sac fungus causes leaf spot disease black Sigatoka in banana plants
ringworm transmitted through direct contact
athletes foot
how are communicable pathogens transmitted directly
inhalation
skin to skin contact or exchange of fluids
penetrate skin actively using enzymes or passively
how are communicable pathogens transmitted indirectly
consumption of contaminated foods
via a vector
spores
how do living conditions affect transmission
overcrowding increases direct transmission
climate determines which organisms can survive
social factors determine how quickly people are treated
name 4 physical barriers to pathogen entry in plants
cellulose cell walls
lignified layer
waxy upper cuticle
old vascular tissue blocked to prevent pathogens from spreading inside plant
describe 2 mechanical responses to infection in plants
guard cells close stomata
thick polysaccharide callose is produced and deposited between cell wall and plasma membrane to increase entry distance
what is necrosis
injury activates intracellular enzymes in plants that kill cells near the site of infection to prevent pathogen from spreading
describe the chemical defences plant use
terpenoids-act as antibacterials
phenols-interfere with digestion
alkaloids-provide bad tastes
defensins- inhibit transport channels hydrolytic enzymes-break down cell wall of invading organism
name 5 barriers to infection in animals
skin is tough keratin layer
blood clotting prevents pathogens entering through skin lesions
hydrochloric acid in stomach kills bacteria
harmless bacteria increase interspecific competition with pathogens
mucous membranes trap pathogen
what are expulsive reflexes
body attempts to force foreign substances out
outline the process of inflammation
damaged vessels release histamines causing vasodilation
blood flow and permeability of blood vessels increases
white blood cells and plasma move into infected cells
how does blood clotting occur
blood platelets form plug and release chemicals that enhance clotting prothombin changes into thrombin-its active form
fibrinogen changes into insoluble fibres which covers wound
how does phagocytosis destroy pathogens
phagocyte moves towards pathogen which may have been marked by opsonins
phagocyte engulfs pathogen via endocytosis to form a phagosome
phagosome fuses with lysosome (phagolysosome)
lysozomes digest pathogens
phagocyte absorbs the products from pathogen hydrolysis
explain the role of antigen presenting cells
macrophage displays antigen from pathogen on its surface
enhances recognition by Th cells which cannot directly interfere with pathogens
secrete cytokines involved in stimulating specific immune response
what are lysozymes
digestive enzymes
found in lysosomes and secretions
damage bacterial cell walls causing osmotic lysis
name the two types of specific immune system
cell mediated
humoral
outline the process of cell mediated response
complementary Th lymphocytes bind to foreign antigens on APC
cell signalling via secretion of interleukins stimulates
-clonal expansion of Th cells: become memory cells or trigger humoral responses
-clonal expansion of cytotoxic T cells: secrete perforin to destroy infected cells
outline the process of humoral response
complementary Th lymphocyte bind to foreign antigens on antigen presenting T cells
release cytokines that stimulate cell expansion of complementary B lymphocytes
B cells differentiate into plasma cells plasma cells secrete antibodies with complementary variable region to antigen
describe the structure and function of B and T lymphocytes
many specific receptors and immunoglobulins on surface
B cells differentiate into plasma cells to secrete antibodies
what are the three types of T cells and their function
T helper cells-secrete cytokines
T killer cells-secrete perforin
T regulator cells-suppress other immune cells to prevent autoimmune disease
what is an antibody
protein secreted by plasma cells
describe the structure of an antibody
quaternary structure: two light chains held by disulfide bridges and 2 longer heavy chains
binding sites on variable regions of light chains have specific tertiary structure complementary to an antigen
how do antibodies lead to the destruction of a pathogen
agglutinins form antigen-antibody complexes to enhance phagocytosis
opsonins mark microbes for phagocytes
antitoxins make toxins insoluble via precipitation
what are memory cells
specialised T/B cells produced from primary immune response
remain in low levels in the blood
can divide rapidly by mitosis if an organism encounters the same pathogen again
contrast the primary and secondary immune response
secondary reponse:
faster rate of antibody production
higher antibody concentration
antibody levels remain higher
pathogen usually destroyed before symptoms
compare and contrast active and passive immunity
both involve antibodies
active:
memory cells=long term
time lag
lymphocytes produce antibodies
needs direct contact with antigen
passive:
no memory cells=long term
immediate
antibodies from external source
no direct contact with antigen
give examples of passive immunity
passive natural=antibodies in breast milk
passive artificial=needle stick injections
give examples of active immunity
active natural=humoral response
active artificial=vaccinations
define autoimmune disease
immune system produces antibodies against own tissue
example=lupus results in inflammation throughout the body
explain the principles of vaccination
vaccine contains dead/ inactive form of pathogen
triggers primary immune response
memory cells produced and remain in the bloodstream so secondary response is rapid and produces high concentrations of antibodies
pathogen in secondary response is destroyed without symptoms
define endemic
disease occurs routinely in a geographical area
define epidemic
temporary rapid increase in incidence of a disease in a geographical area
what role do vaccines play in preventing epidemics
routine vaccination reduces available carriers of pathogen resulting in herd immunity
vaccinating close contacts of infected individuals limits spread of pathogen
list some possible natural sources of medicines
fungi (penicillin)
plants
what is personalised medicine
genome sequencing has enabled scientists to predict an individuals response to disease/medicines so prescriptions targeted
what is synthetic biology
engineering that targets biochemical processes
what are the benefits of using antibiotics
effectively reduce population of bacterial colony
bacteriostatic antibiotics-prevent protein synthesis
bactericidal antibiotics-prevent formation of peptidoglycan cross links in cell walls
what are the risks of using antibiotics
overuse increases selection pressure for resistant strains
antibiotic resistant infections are difficult to treat
