12 - Communicable Diseases 🦠 Flashcards
(156 cards)
1
Q
What are communicable diseases?
A
Ones that spread from an infected person to another by infective organisms known as pathogens
2
Q
What do vectors do?
A
Carry pathogens from one organism to another
3
Q
Bacteria
What 2 ways can bacteria be classified?
A
- by their basic shapes
- by their cell walls
4
Q
Bacteria
What are the ways a bacteria can be shaped?
A
- rod-shaped (bacilli)
- spherical (cocci)
- comma shaped (vibrios)
- spiralled (spirilla)
- corkscrew (spirochaetes)
5
Q
Bacteria
Why can bacteria be classified by their cell walls?
A
Different types of cell wall react differently to gram staining
6
Q
Bacteria
What do gram positive bacteria look like?
A
Purple-blue under a light microscope
7
Q
Bacteria
What do gram negative bacteria look like?
A
Appear red under a light microscope
8
Q
Bacteria
Why is it useful to know what cell wall bacteria have?
A
As the cell wall affects how bacteria react to antibiotics
9
Q
Viruses
What is their size?
A
0.02um - 0.3um in diameter, around 50 times smaller than bacteria
10
Q
Viruses
What is the basic structure of a them?
A
Some genetic material surrounded by proteins
11
Q
Viruses
How do viruses spread?
A
- invade living cells
- genetic material of virus takes over host cell
- viruses reproduce rapidly
12
Q
Viruses
What makes viruses successful pathogens?
A
They evolve by developing adaptations to their host
13
Q
Viruses
What are all naturally occurring viruses?
A
Pathogenic
14
Q
Viruses
What are bacteriophages?
A
- viruses that attack bacteria
- take over bacteria and use them to replicate
- destroying the bacteria at the same time
15
Q
Protoctista
What are Protista?
A
A group of eukaryotic organisms with a wide variety of feeding methods, including single-called organisms and cells grouped into colonies
16
Q
Protoctista
What are protists that cause disease?
A
Parasitic and use people/plants as hosts
17
Q
Protoctista
How do they spread?
A
Pathogenic protists may need vectors to transfer them or enter directly
18
Q
Fungi
What are fungi?
A
Eukaryotic organisms and multicellular
19
Q
Fungi
What can’t they do?
A
Cant photosynthesise and they digest their food extracellularly before absorbing the nutrients
20
Q
Fungi
What does it mean if many fungi are saprophytes?
A
Means they feed on dead and decaying matter
21
Q
Fungi
What does it mean if some fungi are parasitic?
A
They feed in living plants/animals and are pathogenic
22
Q
Fungi
How do they reproduce?
A
Produce millions of tiny spores which can spread huge distances, allowing them to spread rapidly
23
Q
Fungi
Where is it normally found?
A
On top of leaves, preventing photosynthesis and killing the plant
24
Q
Pathogens - modes of action
How do viruses damage host tissue directly?
A
- take over cell metabolism
- viral genetic material is inserted into host DNA
- bursts out of cells
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Pathogens - modes of action
How do Protoctista damage host tissue directly?
- break cells open as the new generation emerges
- don’t take over genetic material of host
- they simply digest and use cell contents as they reproduce
26
Pathogens - modes of action
How do fungi damage the host tissue directly?
- digests living cells and destroys them
27
Pathogens - modes of action
How do fungi harm tissues with toxins?
By producing toxins which affect the host cells and cause disease
28
Pathogens - modes of action
How does bacteria damage host with toxins?
- some toxins damage just cells by breaking down cell membranes
- some toxins damage/inactivate enzymes
- some interfere with the host cell genetic material so it can’t divide
29
Plant Defences against Pathogens
How do they recognise an attack?
- receptors in cells respond to pathogens
- stimulates the release of signalling molecules that appear to switch on genes in the nucleus
- this triggers cellular responses
30
Plant Defences against Pathogens
What are some examples of cellular responses?
- producing defensive chemicals
- sending alarm signals to unaffected cells
- physically strengthening cell walls
31
Plant Defences against Pathogens
What do plants produce high levels of as a physical defence?
A polysaccharide called callose
32
Plant Defences against Pathogens
What is callose’s structure?
Contains B-1,3 and B-1,6 linkages between glucose monomers
33
Plant Defences against Pathogens
Where/how is callose formed?
Is synthesised and deposited between cell walls and cell membranes in cells next to infected cells
34
Plant Defences against Pathogens
What does callose do initially when it is first synthesised?
Callose papillae (next to cells) act as barriers, preventing pathogens entering cells around the site of infection
35
Plant Defences against Pathogens
What is added to callose as large amounts continues to be deposited in cell walls after in initial infection?
Lignin is added, making the mechanical barrier to invasion even thicker and stronger
36
Plant Defences against Pathogens
What does callose block?
Blocks sieve plates in the phloem, sealing odd the infected part and preventing the spread of pathogens
37
Plant Defences against Pathogens
How does callose separate healthy and unhealthy cells?
Is deposited in the plasmodesmata between infected cells and their neighbours, sealing them off
38
Plant Defences against Pathogens
Give an example of the chemical defence of insect repellent produced by the plant?
Pine resin and citronella from lemon grass
39
Plant Defences against Pathogens
Give an example of an insecticide used by plants as a chemical defence
Pyrethrins - made by chrysanthemums and act as insect neurotoxins
Caffeine - toxic to insects and fungi
40
Plant Defences against Pathogens
What are phenols as a chemical defence?
Antiseptics made in many different plants as an antibacterial compound
41
Plant Defences against Pathogens
What does cotton produce as a chemical defence?
Antibacterial Gossypol
42
Plant Defences against Pathogens
What do chitinases do as a chemical defence?
Enzymes that break down the chitin in fungal cell walls to kill the fungi
43
Plant Defences against Pathogens
Give an example of an anti-oomycetes as a chemical defence
Glucanases - enzymes made by some plants that break down glucans, the polymers found in cell walls of oomycetes
44
Plant Defences against Pathogens
How do plants use general toxins as a chemical defence?
Plants make chemicals that can be broken down to form cyanide compounds when the plant cell is attacked
Cyanide is toxic to most living things
45
Direct transmission of pathogens
Give examples of direct contact
- exchanging bodily fluids
- direct skin-to-skin contact
- microorganisms from faeces
46
Direct transmission of pathogens
How can inoculation transfer pathogens?
- through a break in the skin (HIV/AIDS)
- from an animal bite (rabies)
- puncture wound or sharing needles (septicaemia)
47
Direct transmission of pathogens
How does ingestion transfer disease?
Taking in contaminated food or drink
48
Indirect transmission of pathogens
How does disease travel by fomites?
Inanimate objects such as bedding, socks, or cosmetics
49
Indirect transmission of pathogens
How does disease spread by droplet infection (inhalation)?
Minute droplets of saliva and mucus are expelled from your mouth as you talk, cough or sneeze
50
Can animals and humans pass disease amongst each other?
Yes if in close contact
51
What increases the probability of catching a communicable disease in animals?
- overcrowding
- poor nutrition
- a compromised immune system
- poor waste disposal
- climate change
- culture and infrastructure
- socioeconomic factors
52
Indirect transmission of pathogens
What do vectors do?
Carry a disease from one host to another
53
Transmission of pathogens between plants
How does disease spread by direct transmission?
This involves direct contact of a healthy plant with any plant of a diseased plant
54
Transmission of pathogens between plants
How can soil contamination be an indirect transmission of pathogens?
Some pathogens can survive the composting process so the infection cycle can be completed when contaminated compost is used
55
Transmission of pathogens between plants
How is wind used as a vector?
bacteria, viruses and fungal or oomycete spores may be carried on the wind
56
Transmission of pathogens between plants
How is water used as a vector?
Spores swim in the surface film of water on leaves / raindrop splashes carry pathogens and spores
57
Transmission of pathogens between plants
How are humans used as a vector?
Pathogens and spores are transmitted by hands/clothing/fomites/farming practices and by transporting crops globally
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Transmission of pathogens between plants
How are animals used as a vector?
Insects and birds carry pathogens and spores from one plant to another as they feed
Insects such as aphids inoculate pathogens directly into plant tissue
59
What factors affect the transmission of communicable diseases in plants?
- planting varieties of crops susceptible
- overcrowding
- poor mineral nutrition
- damp, warm conditions increase survival of pathogens
- climate change
60
Plant Diseases
What is ringrot?
Bacteria
61
Plant Diseases
What is tobacco mosaic virus (TMV)?
Virus
62
Plant Diseases
What is potato blight?
a fungus-like protoctista
63
Plant Diseases
What is black sigatoka?
Fungus
64
Animal Diseases
What is TB?
bacteria
65
Animal Diseases
What is bacterial meningitis?
Bacteria
66
Animal Diseases
What is HIV/AIDS?
virus
67
Animal Diseases
What is influenza?
virus
68
Animal Diseases
What is malaria?
protoctista
69
Animal Diseases
What is ringworm?
Fungal
70
Animal Diseases
What is athlete's foot?
Fungal
71
Non-specific Defences
What does the skin produce?
Sebum = an oily substance that inhibits the growth of pathogens
72
Non-specific Defences
What do mucus membranes do?
traps microorganisms and contains lysozymes to destroy bacterial and fungal cell wall
73
Non-specific Defences
What chemicals prevent pathogens from getting into our bodies?
Lysozymes in tears and urine & stomach acid
74
What happens once a blood clot is formed to heal the wound?
Epidermal cells below the scab grow, sealing the wound permanently, while damaged blood vessels regrow
75
What happens once a wound forms?
Platelets come into contact with collagen in skin, adhere and release substances
76
What does serotonin do in blood clotting?
makes the smooth muscle in the walls of blood vessels contract, so they reduce blood supply to the area
77
What does thromboplastin do in blood clotting?
An enzyme that triggers a cascade of reactions resulting in a blood clot
78
What reaction in blood clotting does thromboplastin catalyze?
Ca2+ and prothrombin, which forms thrombin
79
What reaction in blood clotting dos thrombin catalyze?
fibrinogen to fibrin, which forms the clot
80
Inflammatory Response
What activates mast cells?
in damaged tissue
81
Inflammatory Response
What chemicals do mast cells release?
cytokines and histamines
82
Inflammatory Response
What do cytokines do?
attract phagocytes to the site
83
Inflammatory Response
Why do histamines cause redness?
Make blood vessels dilate, increasing localised heat = stops bacteria reproducing
84
Inflammatory Response
Why do histamines cause swelling?
Make blood vessels more leaky, so blood plasma is forced out - this is then tissue fluid, causing swelling
85
Non-specific Defences
How does a fever improve immunity?
- high temp kills pathogens
- specific immune system works faster at higher temps
86
Phagocytosis
Define phagocytes
specialised white cells that engulf and destroy pathogens
87
Phagocytosis
What are the 2 types of phagocytes?
Neutrophils and macrophages
88
Phagocytosis
What does pus consist of?
dead neutrophils and pathogens
89
Phagocytosis
Step 1 = how is the pathogen found?
the pathogen produces chemicals that attract phagocytes
90
Phagocytosis
Step 2 = how does a phagocyte detect a pathogen?
recognizes the non-human foreign proteins on the pathogen
91
Phagocytosis
Step 3 = what happens when the phagocyte reaches the pathogen?
it is engulfed and enclosed in a vacuole called a phagosome
92
Phagocytosis
Step 4 = what happens once a phagosome is formed?
it combines with a lysosome to form a phagolysosome
93
Phagocytosis
Step 5 = what happens once a phagolysosome is formed?
enzymes in the lysosome digests and destroys pathogens
94
Phagocytosis
What happens when a macrophage has digested a pathogen?
it combines antigens from the pathogen surface membrane with glycoproteins in the cytoplasm called the major histocompatibility complex (MHC)
95
Phagocytosis
What does a MHC do?
move the pathogen antigens to the macrophage's own surface membrane, becoming an APC
96
What do cytokines do in an immune response?
- cell-signalling molecules, informing other phagocytes that the body is under attack
- increase body temp
- stimulate the specific immune response
97
What do opsonins do?
chemicals that bind to pathogens and tag them so they can be more easily recognised
98
How do phagocytes and opsonins work together?
phagocytes have receptors on their cell membrane that bind to common opsonins so the pathogen can be engulfed
99
Define antibodies
Y-shaped glycoproteins called immunoglobulins which bind to specific antigens
100
What are the antibody chains called?
heavy and light chains
101
What creates antibody chains?
polypeptide chains
102
How are antibody chains held together?
disulfide bridges
103
How do antibodies bind to antigens?
lock and key mechanism
104
What makes up the binding site of an antibody?
an area of 110 amino acids on both heavy and light chains, known as the variable region
105
What gives an antibody its specificity?
The different binding sites
106
Other than the binding sites, what is the rest of the antibody called?
the constant region = same on all antibodies
107
What is formed when an antibody binds to an antigen?
An antigen-antibody complex
108
What does the hinge region of the antibody provide the molecule?
Flexibility, allowing it to bind to 2 separate antigens
109
How do antibodies act as anti-toxins?
bind to toxins produced by pathogens, making them harmless
110
What do agglutinins do?
causes pathogens to clump together, preventing pathogen spreading through body and making them easier to attack
111
T Lymphocytes
What do T-killer cells produce what chemical?
Perforin
112
T Lymphocytes
How does perforin give T-killer cells their function?
makes holes in the cell membrane of pathogens, so it is freely permeable
113
T Lymphocytes
What are T memory cells part of?
the immunological memory
114
T Lymphocytes
What do T regulator cells do?
suppress the immune system, to ensure the body recognises self antigens and doesn't set up an autoimmune response
115
T Lymphocytes
What chemicals are important in t regulator cells?
Interleukins
116
T Lymphocytes
What do T helper cells have that bind to surface antigens on APCs?
CD4 receptors on their surface membranes
117
T Lymphocytes
What are interleukins?
a type of cytokine
118
T Lymphocytes
How do interleukins help t helper cells?
stimulate B cells, increasing antibody production
119
B Lymphocytes
What are B effector cells?
divide to form the plasma cell clones
120
B Lymphocytes
What do plasma cells do?
produce antibodies to particular antigens and release them into circulation
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B Lymphocytes
How long does an active plasma cell live?
a few days
122
B Lymphocytes
How many antibodies per second does an active plasma cell produce?
2000
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B Lymphocytes
What are B memory cells part of?
immunological memory
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B Lymphocytes
What is humoral immunity?
when the body responds to antigens found outside the cells eg bacteria and fungi
125
B Lymphocytes
What is a feature of antibodies produced by the humoral response?
soluble in blood and tissue fluid, and not attached to cells
126
B Lymphocytes
What is clonal selection in the humoral response?
When activated T helper cells bind to the B cell APC
127
B Lymphocytes
What role do interleukins have in the humoral response?
activate B cells
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B Lymphocytes
What is clonal expansion in humoral response?
activated B cells divide by mitosis to give clones of plasma and memory cells
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B Lymphocytes
Humoral response
What is the primary response?
Cloned plasma cells produce antibodies that fit the antigens on the surface of the pathogen, bind to them
130
Why do we get ill during the primary response?
Our body is trying to identify which antibody is needed for the pathogen
131
B Lymphocytes
Humoral immunity
What is the secondary response?
When B memory cells divide to kill the pathogen fast before symptoms occur
132
T Lymphocytes
What does the cell-mediated response target?
cells that have been changed eg by a virus/cancers
133
T Lymphocytes
What is the first stage in the cell-mediated response?
The formation of APCs
134
T Lymphocytes
What do T helper cells do once they fit the antigen on the APC?
become activated, producing interleukins, which stimulates more T cells to divide
135
T Lymphocytes
What can cloned T cells do?
- develop into T memory cells
- stimulate phagocytosis
- stimulate B cell division
- stimulate the development of a clone of T killer cells
136
What is an autoimmune disease?
When the immune system stops recognising self cells and starts to attack healthy body tissue
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What is natural active immunity?
T and B lymphocytes
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What is natural passive immunity?
The first milk of a mother is called colostrum, and is full of antibodies. The infant gut allows these glycoproteins to pass into the bloodstream without being digested
139
What is artificial active immunity?
Vaccines = stimulating the immune system to make antibodies
140
What is artificial passive immunity?
Inoculation = when antibodies from one individual are extracted and injected into another
141
How is a pathogen in a vaccine made safe?
- killed or inactivated
- attenuated strains (weakened)
- toxins altered and detoxified
- isolated antigens extracted from pathogen
- genetically engineered
142
What does a vaccine do?
Triggers the primary immune response
143
What does a vaccine mean happens when your body comes into contact with a live pathogen?
It’s response is secondary, as it already has encountered it and has memory cells
144
Are vaccines long or short term immunity?
Long term
145
Define an epidemic
Disease spreading across a local or national level
146
Define a pandemic
Disease spreading across countries and continents
147
What is herd immunity?
When a significant number have been vaccinated, giving protection to those who don’t have immunity
148
What can help prevent the spread of a pathogen into the wider population?
Mass vaccination
149
How was penicillin found?
Comes from the mould discovers by Alexander Fleming in 1928
150
How can computers be used to source medicines?
Can create 3D models of molecules to build drugs to target specific pathogens
151
What are pharmacogenetics?
The science of interweaving knowledge of drug actions with personal genetic material
= personalised medicine
152
What does synthetic biology enable?
The use of bacteria as biological factories to genetically modify biology for new purposes of medicine
153
What is selective toxicity?
Antibiotics interfere with the metabolism of the bacteria without affecting the metabolism of human cells
154
Explain how antibiotic resistance occurs
- antibiotic is a selective pressure
- bacteria gene pool has variation due to mutations causing different alleles
- some bacteria are resistant
- resistant bacteria survive and reproduce
- those not resistant die
- the frequency of the allele for resistance increases
- so the antibiotic becomes ineffective
155
Name 2 antibiotic resistant superbugs
MRSA
C.difficile
156
What measures can help reduce antibiotic resistant in the long term?
- minimising use of antibiotics
- good hygiene
