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A level Bio OCR A > 4.1.1 Diseases - responses bit > Flashcards

4.1.1 Diseases - responses bit Flashcards

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1
Q

what causes communicable diseases?

A

pathogens

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2
Q

Types of pathogen

A

bacteria

viruses

fungi

protocista

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3
Q

Tuberculosis (TB)

A

bacteria

affects human and cattle (typically)

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4
Q

Meningitis

A

Bacteria

affects humans

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5
Q

Ring rot

A

bacteria

potatoes, tomatoes

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6
Q

HIV / AIDS

A

virus

humans

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7
Q

Influenza

A

virus

animals (including humans)

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8
Q

Tobacco Mosaic Virus

A

virus

plants

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9
Q

Black sigatoka

A

fungus

banana plants

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10
Q

Ring worm

A

fungus

cattle

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11
Q

Athlete’s foot

A

fungus

humans

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12
Q

Potato / tomato blight

A

protocitist

potatoes / tomatoes

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13
Q

Malaria

A

protoctist

animals (including humans)

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14
Q

Direct transmission

A

when a disease is transmitted directly from one organism to another

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15
Q

How can direct transmission happen:

A
  1. direct contact
  2. inoculation
  3. ingestion
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16
Q

direct transmission - direct contact

A

contact with bodily fluids
- blood, semen, vaginal or infected individuals

skin to skin contact

microorganisms from faeces transmitted on hands

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17
Q

direct transmission - inoculation

A

through a break in the skin

from an animal bite

through a puncture wound sharing needles

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18
Q

Indirect transmission

A

when a disease is transmitted from one organism to another via an intermediate

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19
Q

How can indirect transmission happen:

A
  1. fomites
  2. droplet infection
  3. vectors
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20
Q

Indirect transmission - fomites

A

through inanimate objects

bed, clothes, cosmetics

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21
Q

indirect transmission - droplet infection

A

tiny drops of saliva and mucus transfer pathogens during talking, coughing and sneezing

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22
Q

indirect transmission - vectors

A

transfer pathogens from one organism to other

animals and water

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23
Q

factors affecting transmission

A
  1. living conditions
  2. crowding
  3. social factors
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24
Q

factors affecting transmission - living conditions

A

overcrowded living conditions increase the transmission of diseases

eg. TB spread via droplet infection, increased risk of infection and spread if lots of people in an area

25
Q

factors affecting transmission - climate

A

potato and tomato blight especially common during wet summers
- because the spores need water to spread

malaria most common in tropical countries (humid and hot)
- ideal conditions for mosquitoes (malaria vectors) to breed

26
Q

factors affecting transmission - social factors

A

eg. risk of HIV high in places where there’s limited access to
1. good healthcare
- people less likely to be diagnosed and treated for HIV
- most effective anti-HIV drugs are less likely to be available
- virus more likely to be passed onto other

  1. good health education
    - to inform people about how HIV is transmitted and how it can be avoided
    eg. safe sex practices - condoms
27
Q

Animals defense against disease:

A 
skin
mucous membrane
blood clotting
inflammmation
wound repair
expulsive reflexes
28
Q

Animals defense against disease - skin

A

acts as a physical barrier, blocking pathogens from entering the body

acts as a chemical barrier, produces chemicals that are antimicrobial and can lower pH, inhibiting growth of pathogens

29
Q

Animals defense against disease - mucous membranes

A

protect body openings that are exposed to the environment (mouth, nostrils, ears)

some membranes secrete mucus - a sticky substance that traps pathogens and contains antimicrobial enzymes

30
Q

Animals defense against disease - blood clotting

A

a mesh of protein fibres

plug wounds to prevent pathogen entry and blood loss

formed by a series of chemical reactions that take place when platelets are exposed to damaged blood vessels

31
Q

Animals defense against disease - inflammation

A

swelling, pain, heat and redness

triggered by tissue damage - the damaged tissue releases molecules which increase the permeability of the blood vessels, so they start to leak fluid into the surrounding area

this causes swelling and helps to isolate any pathogens that may have entered the damaged tissue

these molecules also cause vasodilation which increases blood flow to the affected area
- this makes the area hot and brings white blood cells to fight off pathogens that may be present

32
Q

Animals defense against disease - wound repair

A

skin is able to repair itself and reform barrier against pathogen entry

the surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound

the tissue below the wound then contracts to bring the edges of the wound closer together

its is repaired using collagen fibres - too many collagen fibres = scar

33
Q

Animals defense against disease - expulsive reflexes

A

coughing and sneezing

sneeze - when mucous membrane in the nostrils are irritated by dirt or dust

cough - irritation is respiratory tract

an attempt to expel foreign objects, pathogen, from the body

AUTOMATIC

34
Q

Plants defenses against disease:

A

physical

chemical

35
Q

Plants defenses against disease - physical

A
  1. waxy cuticle - barrier to pathogen entry - stops water collecting on leaf which could reduce infection by pathogens that are transferred between plants in water
  2. cell walls - barrier to pathogens that make it past waxy cuticle
  3. callose - a polysaccharide that is deposited between plant cell walls and plasma membranes during times of stress (pathogen invasion) - makes it harder for pathogens to enter cells - callose deposition at the plasmodesmata may limit spread of virus between cells
36
Q

Plants defenses against disease - chemical

A
  1. produce antimicrobial chemicals (including antibiotics) which kill pathogens or inhibit their growth
    - saponins —> destroy cell membranes of fungi and other pathogens
    - phytoalexins —> inhibit growth of fungi and other pathogens
  2. secrete chemicals that are toxic to insects - reduces the amount of insect-feeding on plants and therefore reduces the risk of infection by plant viruses carried by insect vectors
37
Q

what triggers an immune response

A

foreign antigens

38
Q

what are antigens

A

molecules on the surface of cells

its how body identifies cell as foreign

39
Q

what is the non-specific immune response?

A

phagocytes engulf pathogens - PHAGOCYTOSIS

  1. a phagocyte recognise the antigens on a pathogen
  2. the cytoplasm of the phagocyte moves around the pathogen, engulfing it.
    - made easier by opsonins —> molecules in the blood that attach to forgein antigens to aid phagocytosis
  3. the pathogen is now contained in a phagosome (a vesicle) in the cytoplasm of the phagocytes
  4. a lysosome (organelle that conatins digestive enzymes) fuses with the phagosome
    - the enzymes break down the pathogen
  5. the phagocytes then presents the pathogens antigens
    - it sticks the antigens on its surface to active other immune system cells
    - acts as an antigen-presenting cell
40
Q

what are opsonins

A

a molecule in the blood that attach to foreign antigens to aid phagocytosis

work in different ways
- some hide the negative charges on the membrane of the pathogen, making it easier for the negitevly charged pharged phagocytes to get closer to the pathogen

41
Q

what is a phagocyte

A

a type of white blood cell that carries out phagocytosis

found in blood and tissues and carry out the non-specific immune response

42
Q

what are neutrophils

A

a type of phagocyte

the first white blood cells to respond to a pathogen inside the body

move towards a wound in response to signals from cytokines

the cytokines are released by cells at the site of the wound

43
Q

specific immune response - 3 main stages

A
  1. phagocytes activates T lymphocytes
  2. T lymphocytes active B lymphocytes, which divide into plasma cells
  3. plasma cells make more antibodies to a specific antigen
44
Q

specific immune response - phagocytes activates T lymphocytes

A
  1. a T lymphocyte is another type of white blood cell
  2. their surface is covered with receptors
  3. the receptors bind to antigens presented by antigen-presenting cells
  4. each T lymphocyte has a different receptor on its surface
  5. when the receptor on the surface of a T lymphocyte meets a complementary antigen, it binds to it
    - –> so each T lymphocyte will bind to a different antigen
  6. this activates the T lymphocyte —> CLONAL SELECTION
  7. the T lymphocyte then undergoes CLONAL EXPANSION - it divides to produce clones of itself
    - different types of T lymphocytes carry out different functions
45
Q

different types of T lymphocytes

A
  1. T helper cells - these release substances to activate B lymphocytes and T killer cells
  2. T killer cells - these attach to and kill cells that are infected with a virus
  3. T regulatory cells - these suppress the immune response from other white blood cells
    - this helps stop immune system cells form mistakenly attacking the hosts’s body cells
46
Q

specific immune response - T lymphocytes activate B lymphocytes

A
  1. B lymphocytes are covered with protiens called antibodies
  2. antibodies bind to antigens to form an antigen-antibody complex
  3. each B lymphocyte has a different shaped antibody on its surface
  4. when then antibody on the surface of a B lymphocyte meets a complementary shaped antigen, it binds to it
    - so each B lymphocyte will bind to a different antigen
  5. this, together with substances released from T helper cells, activates the B lymphocyte
    - –> CLONAL SELECTION
  6. the activated B lymphocyte divides, by mitosis, into plasma cells and memory cells
    - —> CLONAL EXPANSION
47
Q

specific immune response - plasma cells make more antibodies to a specific antigen

A
  1. plasma cells are clones of the B lymphocytes
  2. they secrete loads of the antibody, specific to the antigen, into the blood
  3. these antibodies will bind to the antigens on the cell surface of the pathogen to form lots of antigen-antibody complex
48
Q

structure of antibodies

A

Variable regions - form the antigen binding sites (differ between antibodies)
- the shape of the variable region is complementary to a particular antigen

Hinge region - allows flexibility when the antibody binds to the antigen

Constant region - allow binding to the receptor on immune system cells
- is the same in all antibodies

Disulfide bridges - the bond that hold the polypeptide chains of the protein together

49
Q

cell signalling

A

how cells communicate

a cell may release a substance that binds to the receptors on another cell - causes a response

50
Q

why is cell signalling important in the immune response

A

helps to activate all the different types of white blood cells that are needed

51
Q

cell signalling - interleukins

A

a type of cytokine

binds to receptors on B lympocytes

this activates the B lymphocytes

eg. T helper cells signal to B lymphocytes that there’s a pathogen in the body

52
Q

How do antibodies help clear infection:

A
  1. agglutinating pathogens
  2. neutralising toxins
  3. preventing the pathogen binding to the human cells
53
Q

How do antibodies help clear infection - agglutinating pathogens

A

each antibody has two binding sites
so an antibody can bind to two pathogens at the same time
the pathogens become clumped together
phagocytes then bind to the antibodies and engluf lots of pathogens all at once

54
Q

How do antibodies help clear infection - neutralising toxins

A

toxins have different shapes
antibodies called anti-toxins bind to the toxins produced by pathogens
this prevents toxins from affecting human cells, so toxins are neutralised
the toxin-antibody complexes are also phagocytosed

55
Q

How do antibodies help clear infection - preventing the pathogens binding to human cells

A

when antibodies bind to the antigens on the pathogens, they may block the cell surface receptors that the pathogens need to bind to the host cells
so the pathogens cant attach to or infect the host cells

56
Q

primary response

A

slow

  1. when a pathogens enter the body for the first time the antigens on its surface activates the immune system
  2. arent many B lymphocytes that can make make the needed antibody
  3. eventually body will produce enough of the right antibody to overcome the infection
    - –> meanwhile the infected person will show symptoms of the disease
  4. after being exposed to an antigen —> T and B memory cells
  5. the person is now immune - immune system has the ability to respond quickly to a second infection
57
Q

T and B memory cells

A

remain in the body for a long time

remember the specific antigen and will recognise it a second time round

memory B record the specific antibodies needed to bind the antigen

58
Q

Secondary response

A

if the same pathogen enters the body again, the immune system will produce a stronger, quicker immune response

clonal selection happens faster

  • –> memory B activated and divide into plasma cells that produce the right antibody to the antigen
  • –> memory T activated and divide into the correct type of T lymphocyte to kill the cell carrying the antigen

gets rid of symptoms before you begin to show any symptoms

59
Q

blood smears - what do you see

A

red blood cells - dont have a nucleus

platelets - fragments of cells

white blood cells:
Lymphocyte - smaller than neutrophil, nucleus takes up most of the cell, little cytoplasm + not grainy

Neutrophil - nucleus looks like three interconnected blobs (multi-lobed), cytoplasm grainy

Monocyte - biggest wbc, type of phagocyte, kidney bean shaped nucleus, cytoplasm not grainy

A level Bio OCR A (12 decks)

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