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ocr a level biology > module 4 - communicable diseases, disease prevention & the immune system > Flashcards

module 4 - communicable diseases, disease prevention & the immune system Flashcards

1
Q

define the term ‘communicable disease’

A
  • a disease that can be spread between two organisms
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2
Q

what is a pathogen?

A
  • the organism that causes the disease
  • these include : bacteria, viruses, fungi etc.
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3
Q

BACTERIAL DISEASE - name the diseases that are caused by bacteria in plants and animals

A
  • ring rot disease of plants affects potatoes and tomatoes
  • tuberculosis disease affects animals (humans and cattle)
  • bacterial meningitis disease affects the humans
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4
Q

VIRAL DISEASES - name the viral diseases in plants and animals

A
  • tobacco mosaic disease affects the plants
  • HIV/AIDS disease affects the humans
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5
Q

PROTOCTISTA DISEASE - name the diseases caused by protoctists in plants and animals

A
  • potato/tomato late blight disease affects the plants (tomatoes/potatoes)
  • malaria caused by protoctist affects animals including humans
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6
Q

FUNGAL DISEASES - name the diseases cased by fungi in plants and animals

A
  • black sigatoka disease affects the banana plants
  • ringworm disease affects cattle
  • athlete’s foot disease affects humans
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7
Q

MEANS OF TRANSMISSION - define the term ‘direct transmission’

A
  • when disease is transmitted directly from one organism to another
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8
Q

state how the following diseases are transmitted :
HIV
Influenza
Athlete’s foot

A
  • sexual intercourse
  • coughing or sneezing droplets of mucus (droplet infection)
  • touch
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9
Q

define the term ‘indirect transmission’

A
  • when disease is transmitted directly from one organism to another via an intermediate (air,water,food or another organism called a vector)
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10
Q

describe how potato/tomato late blight is transmitted

A
  • TRANSMISSION : spores (asexual reproductive units)
  • VECTOR : first air, then water
  • PROCESS OF TRANSMISSION : when spores are carried between plants
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11
Q

describe how malaria is transmitted

A
  • TRANSMISSION : blood
  • VECTOR : female mosquitoes
  • PROCESS OF TRANSMISSION : when blood of infected persons are carried between organisms
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12
Q

LIVING CONDITIONS, CLIMATE, SOCIAL FACTORS - explain how overcrowded living conditions can affect disease transmission

A
  • increases the spread of many infectious diseases
    —> EXAMPLE : the risk of TB infection increases when lots of people live crowded together in a small place
    —> this is because bacteria can remain in air for long periods and can infect new people
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13
Q

explain how climate can affect disease transmission

A
  • can also increase the spread of many infectious diseases
    —> EXAMPLE : during wet summers, potato/tomato late blight is more common because spores need water to spread
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14
Q

explain how social factors can affect disease transmission

A
  • can also increase the spread of many infectious diseases
    —> EXAMPLE : the risk of HIV infection is high in areas where the people are less aware of the knowledge about disease transmission, there is no good healthcare
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15
Q

PLANT DEFENCE AGAINST PATHOGENS - name the physical defences and describe them

A
  • WAXY CUTICLE over plant stem and leaf provides a physical barrier against the pathogen entry. it also helps to reduce the risk of infection between plants as it doesn’t allow water to stay on the leaf
  • CELL WALL also acts as a physical barrier for the pathogens that make it past the waxy cuticle
  • during pathogen infection CALLOSE (POLYSACCHARIDE) gets deposited between the plant cell wall and the plasma membrane that make it difficult for the pathogen to enter the cell
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16
Q

describe the chemical defences by secretion of chemicals

A
  • plants secrete TOXINS which kill the insect reducing the risk of infection by plant viruses carried by them
  • SAPONINS are chemical produced by some plants to destroy the cell membrane of pathogens
17
Q

ANIMAL DEFENCES (primary, non-specific) AGAINST PATHOGENS - describe the function of skin

A
  • blocks the entry of pathogen
  • produce chemicals which can inhibit the growth of pathogens by lowering the pH
18
Q

describe the function of blood clotting

A
  • prevents pathogen entry and blood loss by plugging the wound
19
Q

describe the function of wound repair

A
  • outer layer of skin cells divide and migrate to the edges of the wound
  • tissue below the wound having collagen fibres contracts to bring the edges of the wound close together and wound is repaired leaving a scar
20
Q

describe the function of inflammation

A
  • occurs as a result of tissue damage
  • include swelling, pain, heat and redness of the affected area due to release of molecules from the damaged tissue, which helps in isolation of any pathogen and also brings WBCs to the area
21
Q

describe the function of expulsive reflexes

A
  • sneezing and coughing as a result of irritation of membrane of nostril and respiratory tract are an attempt to expel the foreign substances automatically
22
Q

describe the function of the mucous membrane

A
  • protects body openings such as mouth, nostril, ears etc.
  • mucus (sticky substance) secreted by some membranes trap the pathogens
23
Q

STRUCTURE & MODE OF ACTION OF PHAGOCYTES - what is the non-specific immune response carried out by?

A
  • is carried out by phagocytes (macrophage and neutrophils) by a process called phagocytosis
24
Q

describe the process of phagocytosis

A
  • phagocytes recognise the foreign antigen on pathogen and engulf them by extending pseudopodia around them
  • pathogen contained in a vesicle called phagosome fuses with a lysosome, which contains hydrolytic enzymes to digest the contents of the phagosome
  • phagocyte acts as antigen presenting cell (APC) by displaying the antigen on its surface to activate other cells of immune system
25
Q

what are neutrophils and describe their role in the non-specific immune response

A
  • neutrophils also act as phagocytes that respond to pathogens inside the body
  • cytokines released by the cells at the site of the wound signal the neutrophil to move towards a wound and start the process of phagocytosis
26
Q

SPECIFIC IMMUNE RESPONSE - when does this happen?

A
  • happens after the non-specific response and is an attack aimed at a particular antigen
  • it involves the activation of two types of immune cells : T lymphocytes and B lymphocytes
27
Q

what are T lymphocytes?

A
  • white blood cell which contain receptors on their cell surface
  • different T cells have different shaped receptors on their surface (so they will each bind to a different shaped antigen)
28
Q

what happens when a particular T cell binds to a complementary antigen?

A
  • the T cell will become activated
  • this is called CLONAL SELECTION
29
Q

what happens once the T cell is activated?

A
  • the T cell divides by mitosis to produce clones of itself
  • this is called by CLONAL EXPANSION
30
Q

name the different types of T cells which play different roles in the immune response

A
  • T helper cells
  • T killer cells
  • T regulatory cells
  • T memory cells
31
Q

describe the function of T helper cells

A
  • release chemicals (release a type of cytokine called interleukins) to activate B lymphocytes
32
Q

describe the function of T killer cells

A
  • destroy any cells which have been infected with the pathogen
33
Q

describe the function of T regulatory cells

A
  • suppress other immune cells and prevent them from attacking our own (host) cells
34
Q

describe the function of T memory cells

A
  • remain in the bloodstream in low levels in case reinfection occurs
  • if the antigen is detected again at a later date, they will divide into T helper, T killer and T regulatory cells
35
Q

B LYMPHOCYTE RESPONSE - when are B cells activated?

A
  • cells are activated when chemicals are released from T helper cells
  • they are also activated when the antibody molecules on their surface bind to a complementary antigen
36
Q

describe the nature of the antibodies on the surface of different B cells

A
  • different B cells have different shaped antibodies on their surface, so only B cells with the correct-shaped antibodies will be activated.
37
Q

what happens once the B cells are activated?

A
  • the B cells divide by mitosis and differentiate into two kinds of cell, plasma cells and memory cells
38
Q

describe the function of B plasma cells

A
  • produce antibodies with a complementary shape to the antigen
39
Q

describe the function of B memory cells

A
  • remain in the bloodstream in low levels in case reinfection occurs.
  • if the antigen is detected again at a later date, they will quickly divide into plasma cells

ocr a level biology (7 decks)

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