4.1

Question 1

what is a pathogen

Answer 1

microorganisms that cause disease and the organism they occupy is called a host

Question 2

how do bacteria cause disease

Answer 2

they can reproduce quickly and cause damage to cells or release toxins

Question 3

how do fungi cause disease

Answer 3

its hyphae form a mycelium griwth under the skin

in plants fungi live in vascular tissue of the plant where it can gain nutrients

Question 4

how do viruses cause disease

Answer 4

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

Question 5

how do protoctista cause disease

Answer 5

they enter host cells and feed on the contents as they grow

Question 6

what are 3 diseases caused by bacteria

Answer 6

• tuberculosis
• bacterial meningitis
• ring rot (in plants)

Question 7

what are 3 diseases caused by viruses

Answer 7

• HIV?AIDS
• influenza
• tobacco mosaic virus (in plants)

Question 8

what are 3 fungus diseases

Answer 8

• Athletes foot
• Ringworm
• black stigota (in bananas)

Question 9

what are 2 protoctista viruses

Answer 9

• Malaria

- blight (in plants)

Question 10

what are the four stages of the pathogen life cycle

Answer 10

• travel from one host to another(transmission)
• entering the host’s tissue
• reproducing
• leaving the host’s tissue

Question 11

what is the most common form of transmission

Answer 11

direct transmission

Question 12

what are 4 means of direct transmission

Answer 12

• 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

Question 13

what factors affect transmission

Answer 13

-overcrowding
-poor ventilation
-poor diet
poor hygiene

Question 14

what is a vector

Answer 14

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

Question 15

how can pathogens be transmitted indirectly

Answer 15

through a vector

Question 16

how are plant pathogens spread

Answer 16

most are spread directly as they are present in the soil or indirectly through insect bite

Question 17

how is climate linked to diseases

Answer 17

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

Question 18

what are passive defences

Answer 18

defences present before infection

Question 19

what are the 2 categories of passive defences

Answer 19

physical defences

chemical defences

Question 20

what are 3 types of physical defences in plants

Answer 20

callose- large polysaccharide deposit that blocks sieve tube elements

tylose- balloon like projection that blocks the xylem vessles

-bark

Question 21

what are some types of active defences in plants against pathogens

Answer 21

cell walls thicken and strengthen

deposits of callose near invading pathogen

increase in production of chemicals

Question 22

3 types of chemicals used in plants against pathogens

Answer 22

terpenoids

tannins

alkaloids

Question 23

what do terpenoids do

Answer 23

oils that have antibacterial propeties

create scent in mint plants

Question 24

what do tannins do

Answer 24

insects that digest high amounts of tannins in bark die which helps stop pathogen transmission

Question 25

what do alkaloids do

Answer 25

they give a bitter taste to inhibit herbivores feeding inhibit protein synthesis

Question 26

what is necrosis

Answer 26

deliberate cell suicide, if the plant sacrifices cells around the infection the pathogen will be stopped from spreading

Question 27

what is canker

Answer 27

necrosis that causes death of the cambium tissue in the bark

Question 28

what are primary defences

Answer 28

mechanims that prevent entry of the pathogen and are non-specific ( so work the same for every pathogen )

Question 29

what are 5 types of primary defense

Answer 29

- skin - blood clotting - mucus - coughing / sneezing - inflamation

Question 30

what does the skin do to protect against pathogens

Answer 30

contains layers of cells | dead skin cells trap pathogens and fall off

Question 31

how does blood clotting help protect against pahtogens

Answer 31

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

Question 32

how does mucus protect against pathogens

Answer 32

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

Question 33

what does coughing and sneezing do to remove pathogens

Answer 33

sudden explusions of air remove pathogens

Question 34

what are secondary defences used for

Answer 34

mechanisms that combat pathogens once they have entered the body bu are still non-specific

Question 35

what are opsonins

Answer 35

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

Question 36

what are 2 types of phagocytes

Answer 36

neutophills | macrophages

Question 37

what do neutrophils do

Answer 37

- bind to opsonin attached to antigen of pathogen - engulf it by endocytosis - lysososmes release lytic enzymes that digest pathogen - harmless products release

Question 38

what to macrophages do

Answer 38

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

Question 39

what is clonal expansion

Answer 39

an increase in the number of b and t cells through mitosis

Question 40

what is clonal selection

Answer 40

activation of specific b and t cells

Question 41

what does the specifc immune response involve

Answer 41

t lymphocytes | b lymphocytes

Question 42

what do t helper cells do

Answer 42

- release cytokines (chemical messangers) that stimulate b cells to develop - stimulate phagocytosis by phagocytes

Question 43

what do t killer cells do

Answer 43

attack and kills cells that display the foreign antigen

Question 44

what do t memeory cells do

Answer 44

stay iin blood to provide long term immunity

Question 45

what do t regulatory cells do

Answer 45

shut down the immune response after the pathogen has been successfully removed

Question 46

what do plasma cells do (B cells)

Answer 46

circulate in the blood producing antibodies

Question 47

what do b memory cells do

Answer 47

stay in blood providing long term immunity

Question 48

what is cell signalling and why is it useful

Answer 48

release of cytokines that help cells coordinate activities

Question 49

what do monokines do

Answer 49

monokines from macrophages attract neutrophils

Question 50

what do interleukin do

Answer 50

stimulate clonal expansion

Question 51

what are autoimmune diseases

Answer 51

when the immune system attacks our own cells

Question 52

what are 2 autoimmune diseases

Answer 52

arthritis- inflammation of the joint | lupus- affects any part of the body causing swelling and pain