4.1 Flashcards
what is a pathogen
microorganisms that cause disease and the organism they occupy is called a host
how do bacteria cause disease
they can reproduce quickly and cause damage to cells or release toxins
how do fungi cause disease
its hyphae form a mycelium griwth under the skin
in plants fungi live in vascular tissue of the plant where it can gain nutrients
how do viruses cause disease
viruses invade the cell and take over the genetic machinery and cause the cell to make more copies of the virus
host cell bursts releasing new virus cells to take over healthy cells
how do protoctista cause disease
they enter host cells and feed on the contents as they grow
what are 3 diseases caused by bacteria
- tuberculosis
- bacterial meningitis
- ring rot (in plants)
what are 3 diseases caused by viruses
- HIV?AIDS
- influenza
- tobacco mosaic virus (in plants)
what are 3 fungus diseases
- Athletes foot
- Ringworm
- black stigota (in bananas)
what are 2 protoctista viruses
- Malaria
- blight (in plants)
what are the four stages of the pathogen life cycle
- travel from one host to another(transmission)
- entering the host’s tissue
- reproducing
- leaving the host’s tissue
what is the most common form of transmission
direct transmission
what are 4 means of direct transmission
- direct physical contact such as touching somone
- faecal oral transmission, eating food or water contaminated by pathogen
- droplet infection, pathogen is carried in the air in water droplets
=transmission by spores
what factors affect transmission
-overcrowding
-poor ventilation
-poor diet
poor hygiene
what is a vector
another organism that may be used by the pathogen to gain entry to the primary host. For example the parasuite that causes malaria enters the human host through a mosquito bite
how can pathogens be transmitted indirectly
through a vector
how are plant pathogens spread
most are spread directly as they are present in the soil or indirectly through insect bite
how is climate linked to diseases
many pathogens grow and reproduce more rapidly in warm conditions therefore there is a greater variety of diseases to be found in warm climates as cold climates kill these pathogens
what are passive defences
defences present before infection
what are the 2 categories of passive defences
physical defences
chemical defences
what are 3 types of physical defences in plants
callose- large polysaccharide deposit that blocks sieve tube elements
tylose- balloon like projection that blocks the xylem vessles
-bark
what are some types of active defences in plants against pathogens
cell walls thicken and strengthen
deposits of callose near invading pathogen
increase in production of chemicals
3 types of chemicals used in plants against pathogens
terpenoids
tannins
alkaloids
what do terpenoids do
oils that have antibacterial propeties
create scent in mint plants
what do tannins do
insects that digest high amounts of tannins in bark die which helps stop pathogen transmission
what do alkaloids do
they give a bitter taste to inhibit herbivores feeding
inhibit protein synthesis
what is necrosis
deliberate cell suicide, if the plant sacrifices cells around the infection the pathogen will be stopped from spreading
what is canker
necrosis that causes death of the cambium tissue in the bark
what are primary defences
mechanims that prevent entry of the pathogen and are non-specific ( so work the same for every pathogen )
what are 5 types of primary defense
- skin
- blood clotting
- mucus
- coughing / sneezing
- inflamation
what does the skin do to protect against pathogens
contains layers of cells
dead skin cells trap pathogens and fall off
how does blood clotting help protect against pahtogens
blood cuts will form at the site of a cut
this will dry and form a scab
this creates a barrier against infection until new skin is formed
how does mucus protect against pathogens
goblet cells release mucus which traps pathogens and ciliated cells waft the mucus along and out of the body or will get destroyed by the stomaach
what does coughing and sneezing do to remove pathogens
sudden explusions of air remove pathogens
what are secondary defences used for
mechanisms that combat pathogens once they have entered the body bu are still non-specific
what are opsonins
protein molecules that attach to antigens on the surface of a pathogen, they are a type of antibody
they aid phagocytic cells to engulf the pathogens
what are 2 types of phagocytes
neutophills
macrophages
what do neutrophils do
- bind to opsonin attached to antigen of pathogen
- engulf it by endocytosis
- lysososmes release lytic enzymes that digest pathogen
- harmless products release
what to macrophages do
macrophages engulf a pathogen but do not fully digest it
pathogens antigen moves to sufrace of macrophage so becomes an antigen-presenting cell so other cells of the immune system can recognise the cell
what is clonal expansion
an increase in the number of b and t cells through mitosis
what is clonal selection
activation of specific b and t cells
what does the specifc immune response involve
t lymphocytes
b lymphocytes
what do t helper cells do
- release cytokines (chemical messangers) that stimulate b cells to develop
- stimulate phagocytosis by phagocytes
what do t killer cells do
attack and kills cells that display the foreign antigen
what do t memeory cells do
stay iin blood to provide long term immunity
what do t regulatory cells do
shut down the immune response after the pathogen has been successfully removed
what do plasma cells do (B cells)
circulate in the blood producing antibodies
what do b memory cells do
stay in blood providing long term immunity
what is cell signalling and why is it useful
release of cytokines that help cells coordinate activities
what do monokines do
monokines from macrophages attract neutrophils
what do interleukin do
stimulate clonal expansion
what are autoimmune diseases
when the immune system attacks our own cells
what are 2 autoimmune diseases
arthritis- inflammation of the joint
lupus- affects any part of the body causing swelling and pain
