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A-level Biology > 12 - Communicable Diseases 🦠 > Flashcards

12 - Communicable Diseases 🦠 Flashcards

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1
Q

What are communicable diseases?

A

Ones that spread from an infected person to another by infective organisms known as pathogens

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2
Q

What do vectors do?

A

Carry pathogens from one organism to another

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3
Q

Bacteria

What 2 ways can bacteria be classified?

A
  • by their basic shapes
  • by their cell walls
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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)
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5
Q

Bacteria

Why can bacteria be classified by their cell walls?

A

Different types of cell wall react differently to gram staining

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6
Q

Bacteria

What do gram positive bacteria look like?

A

Purple-blue under a light microscope

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7
Q

Bacteria

What do gram negative bacteria look like?

A

Appear red under a light microscope

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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

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9
Q

Viruses

What is their size?

A

0.02um - 0.3um in diameter, around 50 times smaller than bacteria

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10
Q

Viruses

What is the basic structure of a them?

A

Some genetic material surrounded by proteins

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11
Q

Viruses

How do viruses spread?

A
  • invade living cells
  • genetic material of virus takes over host cell
  • viruses reproduce rapidly
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12
Q

Viruses

What makes viruses successful pathogens?

A

They evolve by developing adaptations to their host

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13
Q

Viruses

What are all naturally occurring viruses?

A

Pathogenic

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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
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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

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16
Q

Protoctista

What are protists that cause disease?

A

Parasitic and use people/plants as hosts

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17
Q

Protoctista

How do they spread?

A

Pathogenic protists may need vectors to transfer them or enter directly

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18
Q

Fungi

What are fungi?

A

Eukaryotic organisms and multicellular

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19
Q

Fungi

What can’t they do?

A

Cant photosynthesise and they digest their food extracellularly before absorbing the nutrients

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20
Q

Fungi

What does it mean if many fungi are saprophytes?

A

Means they feed on dead and decaying matter

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21
Q

Fungi

What does it mean if some fungi are parasitic?

A

They feed in living plants/animals and are pathogenic

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22
Q

Fungi

How do they reproduce?

A

Produce millions of tiny spores which can spread huge distances, allowing them to spread rapidly

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23
Q

Fungi

Where is it normally found?

A

On top of leaves, preventing photosynthesis and killing the plant

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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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25
Q

Pathogens - modes of action

How do Protoctista damage host tissue directly?

A
  • 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
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26
Q

Pathogens - modes of action

How do fungi damage the host tissue directly?

A
  • digests living cells and destroys them
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27
Q

Pathogens - modes of action

How do fungi harm tissues with toxins?

A

By producing toxins which affect the host cells and cause disease

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28
Q

Pathogens - modes of action

How does bacteria damage host with toxins?

A
  • 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
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29
Q

Plant Defences against Pathogens

How do they recognise an attack?

A
  • 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
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30
Q

Plant Defences against Pathogens

What are some examples of cellular responses?

A
  • producing defensive chemicals
  • sending alarm signals to unaffected cells
  • physically strengthening cell walls
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31
Q

Plant Defences against Pathogens

What do plants produce high levels of as a physical defence?

A

A polysaccharide called callose

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32
Q

Plant Defences against Pathogens

What is callose’s structure?

A

Contains B-1,3 and B-1,6 linkages between glucose monomers

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33
Q

Plant Defences against Pathogens

Where/how is callose formed?

A

Is synthesised and deposited between cell walls and cell membranes in cells next to infected cells

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34
Q

Plant Defences against Pathogens

What does callose do initially when it is first synthesised?

A

Callose papillae (next to cells) act as barriers, preventing pathogens entering cells around the site of infection

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35
Q

Plant Defences against Pathogens

What is added to callose as large amounts continues to be deposited in cell walls after in initial infection?

A

Lignin is added, making the mechanical barrier to invasion even thicker and stronger

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36
Q

Plant Defences against Pathogens

What does callose block?

A

Blocks sieve plates in the phloem, sealing odd the infected part and preventing the spread of pathogens

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37
Q

Plant Defences against Pathogens

How does callose separate healthy and unhealthy cells?

A

Is deposited in the plasmodesmata between infected cells and their neighbours, sealing them off

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38
Q

Plant Defences against Pathogens

Give an example of the chemical defence of insect repellent produced by the plant?

A

Pine resin and citronella from lemon grass

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39
Q

Plant Defences against Pathogens

Give an example of an insecticide used by plants as a chemical defence

A

Pyrethrins - made by chrysanthemums and act as insect neurotoxins

Caffeine - toxic to insects and fungi

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40
Q

Plant Defences against Pathogens

What are phenols as a chemical defence?

A

Antiseptics made in many different plants as an antibacterial compound

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41
Q

Plant Defences against Pathogens

What does cotton produce as a chemical defence?

A

Antibacterial Gossypol

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42
Q

Plant Defences against Pathogens

What do chitinases do as a chemical defence?

A

Enzymes that break down the chitin in fungal cell walls to kill the fungi

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43
Q

Plant Defences against Pathogens

Give an example of an anti-oomycetes as a chemical defence

A

Glucanases - enzymes made by some plants that break down glucans, the polymers found in cell walls of oomycetes

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44
Q

Plant Defences against Pathogens

How do plants use general toxins as a chemical defence?

A

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

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45
Q

Direct transmission of pathogens

Give examples of direct contact

A
  • exchanging bodily fluids
  • direct skin-to-skin contact
  • microorganisms from faeces
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46
Q

Direct transmission of pathogens

How can inoculation transfer pathogens?

A
  • through a break in the skin (HIV/AIDS)
  • from an animal bite (rabies)
  • puncture wound or sharing needles (septicaemia)
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47
Q

Direct transmission of pathogens

How does ingestion transfer disease?

A

Taking in contaminated food or drink

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48
Q

Indirect transmission of pathogens

How does disease travel by fomites?

A

Inanimate objects such as bedding, socks, or cosmetics

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49
Q

Indirect transmission of pathogens

How does disease spread by droplet infection (inhalation)?

A

Minute droplets of saliva and mucus are expelled from your mouth as you talk, cough or sneeze

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50
Q

Can animals and humans pass disease amongst each other?

A

Yes if in close contact

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51
Q

What increases the probability of catching a communicable disease in animals?

A
  • overcrowding
  • poor nutrition
  • a compromised immune system
  • poor waste disposal
  • climate change
  • culture and infrastructure
  • socioeconomic factors
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52
Q

Indirect transmission of pathogens

What do vectors do?

A

Carry a disease from one host to another

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53
Q

Transmission of pathogens between plants

How does disease spread by direct transmission?

A

This involves direct contact of a healthy plant with any plant of a diseased plant

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54
Q

Transmission of pathogens between plants

How can soil contamination be an indirect transmission of pathogens?

A

Some pathogens can survive the composting process so the infection cycle can be completed when contaminated compost is used

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55
Q

Transmission of pathogens between plants

How is wind used as a vector?

A

bacteria, viruses and fungal or oomycete spores may be carried on the wind

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56
Q

Transmission of pathogens between plants

How is water used as a vector?

A

Spores swim in the surface film of water on leaves / raindrop splashes carry pathogens and spores

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57
Q

Transmission of pathogens between plants

How are humans used as a vector?

A

Pathogens and spores are transmitted by hands/clothing/fomites/farming practices and by transporting crops globally

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58
Q

Transmission of pathogens between plants

How are animals used as a vector?

A

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

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59
Q

What factors affect the transmission of communicable diseases in plants?

A
  • planting varieties of crops susceptible
  • overcrowding
  • poor mineral nutrition
  • damp, warm conditions increase survival of pathogens
  • climate change
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60
Q

Plant Diseases

What is ringrot?

A

Bacteria

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61
Q

Plant Diseases

What is tobacco mosaic virus (TMV)?

A

Virus

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62
Q

Plant Diseases

What is potato blight?

A

a fungus-like protoctista

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63
Q

Plant Diseases

What is black sigatoka?

A

Fungus

64
Q

Animal Diseases

What is TB?

A

bacteria

65
Q

Animal Diseases

What is bacterial meningitis?

A

Bacteria

66
Q

Animal Diseases

What is HIV/AIDS?

A

virus

67
Q

Animal Diseases

What is influenza?

A

virus

68
Q

Animal Diseases

What is malaria?

A

protoctista

69
Q

Animal Diseases

What is ringworm?

A

Fungal

70
Q

Animal Diseases

What is athlete’s foot?

A

Fungal

71
Q

Non-specific Defences

What does the skin produce?

A

Sebum = an oily substance that inhibits the growth of pathogens

72
Q

Non-specific Defences

What do mucus membranes do?

A

traps microorganisms and contains lysozymes to destroy bacterial and fungal cell wall

73
Q

Non-specific Defences

What chemicals prevent pathogens from getting into our bodies?

A

Lysozymes in tears and urine & stomach acid

74
Q

What happens once a blood clot is formed to heal the wound?

A

Epidermal cells below the scab grow, sealing the wound permanently, while damaged blood vessels regrow

75
Q

What happens once a wound forms?

A

Platelets come into contact with collagen in skin, adhere and release substances

76
Q

What does serotonin do in blood clotting?

A

makes the smooth muscle in the walls of blood vessels contract, so they reduce blood supply to the area

77
Q

What does thromboplastin do in blood clotting?

A

An enzyme that triggers a cascade of reactions resulting in a blood clot

78
Q

What reaction in blood clotting does thromboplastin catalyze?

A

Ca2+ and prothrombin, which forms thrombin

79
Q

What reaction in blood clotting dos thrombin catalyze?

A

fibrinogen to fibrin, which forms the clot

80
Q

Inflammatory Response

What activates mast cells?

A

in damaged tissue

81
Q

Inflammatory Response

What chemicals do mast cells release?

A

cytokines and histamines

82
Q

Inflammatory Response

What do cytokines do?

A

attract phagocytes to the site

83
Q

Inflammatory Response

Why do histamines cause redness?

A

Make blood vessels dilate, increasing localised heat = stops bacteria reproducing

84
Q

Inflammatory Response

Why do histamines cause swelling?

A

Make blood vessels more leaky, so blood plasma is forced out - this is then tissue fluid, causing swelling

85
Q

Non-specific Defences

How does a fever improve immunity?

A
  • high temp kills pathogens
  • specific immune system works faster at higher temps
86
Q

Phagocytosis

Define phagocytes

A

specialised white cells that engulf and destroy pathogens

87
Q

Phagocytosis

What are the 2 types of phagocytes?

A

Neutrophils and macrophages

88
Q

Phagocytosis

What does pus consist of?

A

dead neutrophils and pathogens

89
Q

Phagocytosis

Step 1 = how is the pathogen found?

A

the pathogen produces chemicals that attract phagocytes

90
Q

Phagocytosis

Step 2 = how does a phagocyte detect a pathogen?

A

recognizes the non-human foreign proteins on the pathogen

91
Q

Phagocytosis

Step 3 = what happens when the phagocyte reaches the pathogen?

A

it is engulfed and enclosed in a vacuole called a phagosome

92
Q

Phagocytosis

Step 4 = what happens once a phagosome is formed?

A

it combines with a lysosome to form a phagolysosome

93
Q

Phagocytosis

Step 5 = what happens once a phagolysosome is formed?

A

enzymes in the lysosome digests and destroys pathogens

94
Q

Phagocytosis

What happens when a macrophage has digested a pathogen?

A

it combines antigens from the pathogen surface membrane with glycoproteins in the cytoplasm called the major histocompatibility complex (MHC)

95
Q

Phagocytosis

What does a MHC do?

A

move the pathogen antigens to the macrophage’s own surface membrane, becoming an APC

96
Q

What do cytokines do in an immune response?

A
  • cell-signalling molecules, informing other phagocytes that the body is under attack
  • increase body temp
  • stimulate the specific immune response
97
Q

What do opsonins do?

A

chemicals that bind to pathogens and tag them so they can be more easily recognised

98
Q

How do phagocytes and opsonins work together?

A

phagocytes have receptors on their cell membrane that bind to common opsonins so the pathogen can be engulfed

99
Q

Define antibodies

A

Y-shaped glycoproteins called immunoglobulins which bind to specific antigens

100
Q

What are the antibody chains called?

A

heavy and light chains

101
Q

What creates antibody chains?

A

polypeptide chains

102
Q

How are antibody chains held together?

A

disulfide bridges

103
Q

How do antibodies bind to antigens?

A

lock and key mechanism

104
Q

What makes up the binding site of an antibody?

A

an area of 110 amino acids on both heavy and light chains, known as the variable region

105
Q

What gives an antibody its specificity?

A

The different binding sites

106
Q

Other than the binding sites, what is the rest of the antibody called?

A

the constant region = same on all antibodies

107
Q

What is formed when an antibody binds to an antigen?

A

An antigen-antibody complex

108
Q

What does the hinge region of the antibody provide the molecule?

A

Flexibility, allowing it to bind to 2 separate antigens

109
Q

How do antibodies act as anti-toxins?

A

bind to toxins produced by pathogens, making them harmless

110
Q

What do agglutinins do?

A

causes pathogens to clump together, preventing pathogen spreading through body and making them easier to attack

111
Q

T Lymphocytes

What do T-killer cells produce what chemical?

A

Perforin

112
Q

T Lymphocytes

How does perforin give T-killer cells their function?

A

makes holes in the cell membrane of pathogens, so it is freely permeable

113
Q

T Lymphocytes

What are T memory cells part of?

A

the immunological memory

114
Q

T Lymphocytes

What do T regulator cells do?

A

suppress the immune system, to ensure the body recognises self antigens and doesn’t set up an autoimmune response

115
Q

T Lymphocytes

What chemicals are important in t regulator cells?

A

Interleukins

116
Q

T Lymphocytes

What do T helper cells have that bind to surface antigens on APCs?

A

CD4 receptors on their surface membranes

117
Q

T Lymphocytes

What are interleukins?

A

a type of cytokine

118
Q

T Lymphocytes

How do interleukins help t helper cells?

A

stimulate B cells, increasing antibody production

119
Q

B Lymphocytes

What are B effector cells?

A

divide to form the plasma cell clones

120
Q

B Lymphocytes

What do plasma cells do?

A

produce antibodies to particular antigens and release them into circulation

121
Q

B Lymphocytes

How long does an active plasma cell live?

A

a few days

122
Q

B Lymphocytes

How many antibodies per second does an active plasma cell produce?

A

2000

123
Q

B Lymphocytes

What are B memory cells part of?

A

immunological memory

124
Q

B Lymphocytes

What is humoral immunity?

A

when the body responds to antigens found outside the cells eg bacteria and fungi

125
Q

B Lymphocytes

What is a feature of antibodies produced by the humoral response?

A

soluble in blood and tissue fluid, and not attached to cells

126
Q

B Lymphocytes

What is clonal selection in the humoral response?

A

When activated T helper cells bind to the B cell APC

127
Q

B Lymphocytes

What role do interleukins have in the humoral response?

A

activate B cells

128
Q

B Lymphocytes

What is clonal expansion in humoral response?

A

activated B cells divide by mitosis to give clones of plasma and memory cells

129
Q

B Lymphocytes

Humoral response

What is the primary response?

A

Cloned plasma cells produce antibodies that fit the antigens on the surface of the pathogen, bind to them

130
Q

Why do we get ill during the primary response?

A

Our body is trying to identify which antibody is needed for the pathogen

131
Q

B Lymphocytes

Humoral immunity

What is the secondary response?

A

When B memory cells divide to kill the pathogen fast before symptoms occur

132
Q

T Lymphocytes

What does the cell-mediated response target?

A

cells that have been changed eg by a virus/cancers

133
Q

T Lymphocytes

What is the first stage in the cell-mediated response?

A

The formation of APCs

134
Q

T Lymphocytes

What do T helper cells do once they fit the antigen on the APC?

A

become activated, producing interleukins, which stimulates more T cells to divide

135
Q

T Lymphocytes

What can cloned T cells do?

A
  • develop into T memory cells
  • stimulate phagocytosis
  • stimulate B cell division
  • stimulate the development of a clone of T killer cells
136
Q

What is an autoimmune disease?

A

When the immune system stops recognising self cells and starts to attack healthy body tissue

137
Q

What is natural active immunity?

A

T and B lymphocytes

138
Q

What is natural passive immunity?

A

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
Q

What is artificial active immunity?

A

Vaccines = stimulating the immune system to make antibodies

140
Q

What is artificial passive immunity?

A

Inoculation = when antibodies from one individual are extracted and injected into another

141
Q

How is a pathogen in a vaccine made safe?

A
  • killed or inactivated
  • attenuated strains (weakened)
  • toxins altered and detoxified
  • isolated antigens extracted from pathogen
  • genetically engineered
142
Q

What does a vaccine do?

A

Triggers the primary immune response

143
Q

What does a vaccine mean happens when your body comes into contact with a live pathogen?

A

It’s response is secondary, as it already has encountered it and has memory cells

144
Q

Are vaccines long or short term immunity?

A

Long term

145
Q

Define an epidemic

A

Disease spreading across a local or national level

146
Q

Define a pandemic

A

Disease spreading across countries and continents

147
Q

What is herd immunity?

A

When a significant number have been vaccinated, giving protection to those who don’t have immunity

148
Q

What can help prevent the spread of a pathogen into the wider population?

A

Mass vaccination

149
Q

How was penicillin found?

A

Comes from the mould discovers by Alexander Fleming in 1928

150
Q

How can computers be used to source medicines?

A

Can create 3D models of molecules to build drugs to target specific pathogens

151
Q

What are pharmacogenetics?

A

The science of interweaving knowledge of drug actions with personal genetic material

= personalised medicine

152
Q

What does synthetic biology enable?

A

The use of bacteria as biological factories to genetically modify biology for new purposes of medicine

153
Q

What is selective toxicity?

A

Antibiotics interfere with the metabolism of the bacteria without affecting the metabolism of human cells

154
Q

Explain how antibiotic resistance occurs

A
  • 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
Q

Name 2 antibiotic resistant superbugs

A

MRSA
C.difficile

156
Q

What measures can help reduce antibiotic resistant in the long term?

A
  • minimising use of antibiotics
  • good hygiene

A-level Biology (23 decks)

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