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A2 Biology OCR > 4.1 > Flashcards

4.1 Flashcards

1
Q

what is a pathogen

A

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

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2
Q

how do bacteria cause disease

A

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

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3
Q

how do fungi cause disease

A

its hyphae form a mycelium griwth under the skin

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

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4
Q

how do viruses cause disease

A

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

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5
Q

how do protoctista cause disease

A

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

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6
Q

what are 3 diseases caused by bacteria

A
  • tuberculosis
  • bacterial meningitis
  • ring rot (in plants)
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7
Q

what are 3 diseases caused by viruses

A
  • HIV?AIDS
  • influenza
  • tobacco mosaic virus (in plants)
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8
Q

what are 3 fungus diseases

A
  • Athletes foot
  • Ringworm
  • black stigota (in bananas)
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9
Q

what are 2 protoctista viruses

A
  • Malaria

- blight (in plants)

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10
Q

what are the four stages of the pathogen life cycle

A
  • travel from one host to another(transmission)
  • entering the host’s tissue
  • reproducing
  • leaving the host’s tissue
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11
Q

what is the most common form of transmission

A

direct transmission

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12
Q

what are 4 means of direct transmission

A
  • 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

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13
Q

what factors affect transmission

A

-overcrowding
-poor ventilation
-poor diet
poor hygiene

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14
Q

what is a vector

A

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

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15
Q

how can pathogens be transmitted indirectly

A

through a vector

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16
Q

how are plant pathogens spread

A

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

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17
Q

how is climate linked to diseases

A

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

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18
Q

what are passive defences

A

defences present before infection

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19
Q

what are the 2 categories of passive defences

A

physical defences

chemical defences

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20
Q

what are 3 types of physical defences in plants

A

callose- large polysaccharide deposit that blocks sieve tube elements

tylose- balloon like projection that blocks the xylem vessles

-bark

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21
Q

what are some types of active defences in plants against pathogens

A

cell walls thicken and strengthen

deposits of callose near invading pathogen

increase in production of chemicals

22
Q

3 types of chemicals used in plants against pathogens

A

terpenoids

tannins

alkaloids

23
Q

what do terpenoids do

A

oils that have antibacterial propeties

create scent in mint plants

24
Q

what do tannins do

A

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

25
Q

what do alkaloids do

A

they give a bitter taste to inhibit herbivores feeding

inhibit protein synthesis

26
Q

what is necrosis

A

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

27
Q

what is canker

A

necrosis that causes death of the cambium tissue in the bark

28
Q

what are primary defences

A

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

29
Q

what are 5 types of primary defense

A
  • skin
  • blood clotting
  • mucus
  • coughing / sneezing
  • inflamation
30
Q

what does the skin do to protect against pathogens

A

contains layers of cells

dead skin cells trap pathogens and fall off

31
Q

how does blood clotting help protect against pahtogens

A

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

32
Q

how does mucus protect against pathogens

A

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

33
Q

what does coughing and sneezing do to remove pathogens

A

sudden explusions of air remove pathogens

34
Q

what are secondary defences used for

A

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

35
Q

what are opsonins

A

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

36
Q

what are 2 types of phagocytes

A

neutophills

macrophages

37
Q

what do neutrophils do

A
  • bind to opsonin attached to antigen of pathogen
  • engulf it by endocytosis
  • lysososmes release lytic enzymes that digest pathogen
  • harmless products release
38
Q

what to macrophages do

A

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

39
Q

what is clonal expansion

A

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

40
Q

what is clonal selection

A

activation of specific b and t cells

41
Q

what does the specifc immune response involve

A

t lymphocytes

b lymphocytes

42
Q

what do t helper cells do

A
  • release cytokines (chemical messangers) that stimulate b cells to develop
  • stimulate phagocytosis by phagocytes
43
Q

what do t killer cells do

A

attack and kills cells that display the foreign antigen

44
Q

what do t memeory cells do

A

stay iin blood to provide long term immunity

45
Q

what do t regulatory cells do

A

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

46
Q

what do plasma cells do (B cells)

A

circulate in the blood producing antibodies

47
Q

what do b memory cells do

A

stay in blood providing long term immunity

48
Q

what is cell signalling and why is it useful

A

release of cytokines that help cells coordinate activities

49
Q

what do monokines do

A

monokines from macrophages attract neutrophils

50
Q

what do interleukin do

A

stimulate clonal expansion

51
Q

what are autoimmune diseases

A

when the immune system attacks our own cells

52
Q

what are 2 autoimmune diseases

A

arthritis- inflammation of the joint

lupus- affects any part of the body causing swelling and pain

A2 Biology OCR (25 decks)

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