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A-Level Biology - OCR A > 4.12 Communicable Diseases > Flashcards

4.12 Communicable Diseases Flashcards

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1
Q

What is a communicable disease?

A

A disease caused by a pathogen

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2
Q

How do pathogens cause harm?

A
  • Damage the tissues - enter cells and destroy them
  • Produce toxins - act as inhibitors to enzymes or other processes which use proteins e.g. protein receptors in synapses
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3
Q

Give 3 examples of bacteria

A

Tuberculosis, Salmonella, Ring rot

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4
Q

Give 3 examples of viruses

A

HIV/AIDS, Influenza, Tobacco Mosaic Virus

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5
Q

Give 3 examples of fungi

A

Ring worm, Athlete’s foot, Black Sigatoka

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6
Q

Give an example of a protoctista

A

Malaria, Potato blight

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7
Q

Define direct transmission in animals

A

Pathogen is transferred directly from one individual to another

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8
Q

Give 3 examples of direct transmission in animals

A
  • Direct contact - kissing & bodily fluids, skin contact, microorganisms
  • Inoculation - through break in skin, animal bite, puncture wound
  • Ingestion - contaminated food, licking fingers
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9
Q

Define indirect transmission

A

Pathogen travels from one individual to another indirectly

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10
Q

Give 3 examples of indirect transmission in animals

A
  • Fomites - inanimate objects e.g. bedding, socks, cosmetics
  • Droplet infection - Minute drops of saliva and mucus from speaking/coughing/sneezing
  • Vectors - transmits communicable pathogens from one host to another e.g. water mosquitoes, fleas.
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11
Q

Outline factors affecting transmission in animals

A
  • Overcrowded living
  • Poor nutrition
  • Compromised immune system
  • Poor disposal of waste
  • Climate change - can introduce new vectors/diseases’
  • Culture and infrastructure - certain medical practices can increase transmission
  • Socioeconomic factors - lack of trained health workers / public warning when outbreak occurs
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12
Q

Define direct transmission in plants

A

Infected plant coming into direct contact with another

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13
Q

Give 2 examples of direct transmission in plants

A
  • Soil contamination - infected plants leave pathogens in soil
  • Vectors
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14
Q

Give 4 examples of vectors (plants)

A
  • Wind - bacteria, viruses, fungal spores can be carried by wind e.g. Black Sigatoka is blown between Caribbean islands
  • Water - spores swim in the surface film of water on leaves; raindrop splashes carry pathogens
  • Animals - insects/birds carry pathogens/spores directly from one plant to another; insects such as aphids directly inoculate pathogens into plant tissue.
  • Humans - hands, clothing farming practices + transport of crops around the world spread pathogens
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15
Q

Outline factors affecting transmission in plants

A
  • Planting crop varieties susceptible to disease
  • Over-crowding increases likelihood of contact
  • Poor mineral nutrition reduces resistance of plants
  • Damp, warm conditions increases survival and spread of pathogens & spores
  • Climate change - increased rainfall and wind promote spread of disease; vectors spread to new areas; drier conditions may reduce spread
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16
Q

What is the non-specific immune system?

A
  • Gives the same response each time the same pathogen attacks
  • Does not distinguish between different pathogens
  • Present from birth
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17
Q

Detail examples of the non-specific immune system

A
  • Epidermis of skin - dead layers of cells & clotting
  • Mucous membranes - protective layer
  • Chemicals such as: lysozyme in tears/urine; HCl in stomach
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18
Q

What is the specific immune system?

A

Involves antibodies and T- and B-Cells

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19
Q

Detail examples of the non-specific immune system

A
  • Epidermis of skin - dead layers of cells & clotting
  • Mucous membranes - protective layer
  • Chemicals such as: lysozyme in tears/urine; HCl in stomach
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20
Q

What are antigens?

A
  • Proteins/molecules on cell surface
  • Generate an immune response
  • System can tell difference between self/non-self due to antigens
  • Not always a good thing; cancers/transplants
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21
Q

What are phagocytes?

A
  • WBCs
  • Continually produced from stem cells on bone marrow
  • Stored in bone marrow
  • Released into blood to engulf pathogens
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22
Q

Name the two types of phagocytes

A

Neutrophils and Macrophages

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23
Q

What are neutrophils?

A
  • 60% of WBCs
  • Smaller than macrophages and short lived
  • Chemotaxic - (Move to chemicals)
  • Numbers increase rapidly during infection and move into tissues through leaky capillary walls.
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24
Q

What are macrophages?

A
  • 4%of WBCs
  • Phagocytic but play a role in activating the specific immune system
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25
Q

How do macrophages work?

A
  • ## Circulate in blood and tend to remain in organs such as lungs, spleen, lymph nodes and kidneys
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26
Q

How do macrophages work?

A
  • Circulate in blood and tend to remain in organs such as lungs, spleen, lymph nodes and kidneys
  • Squeeze through leaky capillary walls
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27
Q

What is opsonisation?

A

The binding of an antibody to the surface of a pathogen to tag the pathogen so that the phagocyte can identify and engulf it
Some opsonins can make pathogen walls leaky so they swell and burst

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28
Q

What are opsonins?

A

Proteins released by the liver and phagocytes which circulate the blood in an inactive state. They are activated in the presence of bacteria and yeasts.

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29
Q

Describe the four mechanisms of opsonins

A
  1. Deposited on membrane of pathogen and make it porous
  2. Stimulate histamine release from mast cells
  3. Attract phagocytes to infection - chemotaxis
  4. Opsonisation
30
Q

How do opsonins function?

A
  • One end of the complement protein binds to a molecule on the bacterial membrane
  • Other end binds to phagocyte
  • As phagocyte binds to complement proteins, the bacterial cell is engulfed
31
Q

What are mast cells?

A

Granular cells found in connective tissue when an injury occurs

32
Q

What do mast cells do?

A
  • Release histamine
  • Release cytokines
33
Q

What does the release of histamine do?

A
  1. Relaxes arterioles to increase blood flow
  2. Makes capillaries more leaky
  3. Attracts phagocytes
  4. Makes sensory neurones more sensitive
34
Q

What are cytokines?

A

Chemicals which attract phagocytes to the site of the the wound which engulf and digest the pathogens

35
Q

Describe the action of phagocytosis

A
  • Complement proteins released by liver and phagocytes help the phagocytes recognise pathogen
  • Phagocytes engulf bacteria (or other debris)
  • Ingested cells are enclosed in a vacuole
  • Lysozymes fuse with vacuole and release hydrolytic enzymes into it
  • The soluble products are then absorbed
36
Q

Describe the action of macrophages

A
  • They become Antigen Presenting Cells (APCs)
  • They combine the antigens from the pathogen with a glycoprotein from the macrophage Major Histocompatability Complexes (MHC)
  • These are positioned on the cell surface membrane to signal to the lymphocytes
37
Q

What are lymphocytes?

A

A part of the specific immune response which learns the antigens of the pathogen so that it can respond to it directly next time

38
Q

How is the cytoskeleton used in phagocytosis?

A
  • Moves the pseudopodia to enable the phagocyte to move
  • Moves the lysosomes towards the phagosome
39
Q

How is ATP used in phagocytosis?

A

Large numbers of mitochondria provide ATP for endocytosis and exocytosis when excreting waste products

40
Q

Outline the structure of an antibody

A

Heavy chain: Contains constant regions and is joined by disulphide bridges
Light chain: Connects to heavy chain via flexible hinge regions; contains specific variable regions connecting to specific antigen

41
Q

How is an antibody specialised to its function?

A
  • Each antibody contains 2 variable regions to connect to 2 of the same antigen
  • Each antibody is complementary to one specific antigen which it can bind to forming an Antigen-Antibody Complex
  • Constant regions are all the same so phagocytes can recognise them
42
Q

What is agglutination?

A

Formation of clumps of cells by antibodies causing microbes to stick together so that phagocytes can engulf them more easily

43
Q

What is neutralisation?

A

Antibodies produce anti-toxins to neutralise toxins released by pathogens

44
Q

What is clonal selection?

A

Part of immune response. Process of choosing the correct lymphocyte to fight the infection - occurs during the ‘lag phase’

45
Q

Outline the process of clonal selection

A

Activated T-helper cells bind to the B-cell with the correct antibody
Interleukins produced by the T-cell helps activate the B-cell

46
Q

Outline the process of clonal expansion

A

The activated B-cell divides via mitosis to give clones of plasma and memory B-cells.

47
Q

Give 4 types of T-Cell (T-lymphocytes)

A
  • T-helper cells
  • T-killer cells
  • T-memory cells
  • T-regulator cells
48
Q

What are T-helper cells?

A
  • Produce interleukins ( a type of cytokine (cell signalling molecule))
  • Interleukins stimulate activity of B cells
  • This then increases antibody production and stimulates production of other T-Cells and stimulates macrophages to engulf pathogens with AA Complexes
49
Q

What are T-killer cells?

A

Destroy the pathogen carrying the antigen
Produce a chemical called perforin which makes holes in pathogen membranes

50
Q

What are T-memory cells?

A

Live for a long time and divide rapidly to form a large number of T-killer cells when met with an antigen for the 2nd time

51
Q

What are T-regulator cells?

A

Supress the immune system to regulate it - they stop the immune response when the pathogen has been eliminated to prevent an autoimmune response

52
Q

Give 3 types of B-Cells (B-lymphocytes)

A
  • Plasma cells
  • B-effector cells
  • B-memory cells
53
Q

What are plasma cells?

A

Produce antibodies for a specific antigen

54
Q

What are B-effector cells?

A

Divide to form plasma cell clones

55
Q

What are B-memory cells?

A

Provide immunological memory for a specific antigen for a very long time

56
Q

Outline the process of clonal expansion

A

The activated B-cell divides via mitosis to give clones of plasma and memory B-cells.

57
Q

What is an autoimmune disease?

A

When the body fails to recognise ‘self’ cells and attacks itself. e.g. Rheumatoid arthritis/type-1 diabetes/lupus

58
Q

Describe the process of inflammation

A
  • Mast cells are activated in damaged tissue
  • They release histamines and cytokines
  • Histamines cause blood vessels to dilate causing localised redness/heat
  • Histamines make blood vessel walls more leaky so tissue fluid is created
  • This causes swelling and pain
  • Cytokines attract phagocytes to the site which dispose of pathogens via phagocytosis
59
Q

Describe the process of cell-mediated immunity

A
  1. Macrophages engulf and digest pathogens in non-specific immune system. They process antigens from surface of pathogen to form APCs
  2. Receptors on T-helper cells fit antigens, they produce interleukins which stimulate more T-cells to divide rapidly by mitosis to form more T-helper cell clones.
  3. Cloned T-cells may: develop into T-memory cells; produce interleukins to stimulate phagocytosis or B-cells to divide or the development of T-killer cells specific to the antigen.
60
Q

Define immunity

A

The means by which the body protects itself from infection

61
Q

Define immunisation

A

The process of artificially creating immunity

62
Q

Give the 4 types of immunity

A
  • Natural active
  • Natural Passive
  • Artificial Active
  • Artificial Passive
63
Q

What is natural active immunity?

A

Organism’s own immune system is stimulated by a disease

64
Q

What is natural passive immunity?

A

Antibodies are passed to an individual e.g. via breastmilk or placenta

65
Q

What is artificial active immunity?

A

Organism’s own immune system is stimulated by a vaccine - dead or weakened pathogen. e.g. polio, MMR.

66
Q

What is artificial passive immunity?

A

Antibodies obtained chemically and administered often by a jab

67
Q

How do vaccinations work?

A

They promote primary response via clonal selection
B- and T-lymphocytes make memory cells which divide via mitosis (clonal expansion)

68
Q

What is herd immunity?

A

The protection gained by a community when vaccination rates are very high

69
Q

Name the two types of passive plant defences against pathogens

A

Physical and chemical

70
Q

Name 5 physical plant barriers

A
  • Wax
  • Cuticle
  • Cell wall
  • Stomata
  • Callose deposition in plasmodesmata to isolate healthy cells from infected ones
71
Q

Name 4 chemical plant barriers

A
  • Nutrient deprivation
  • pH
  • Phytoanticipins
  • Insecticides, antibacterial and antifungal compounds

A-Level Biology - OCR A (16 decks)

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