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Wjec A Level Biology > 4.5 Immunology And Disease > Flashcards

4.5 Immunology And Disease Flashcards

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1
Q

Pathogenic definition

A

An organism that causes damage to its host

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2
Q

Infectious definition

A

A disease that may be passed or transmitted from one individual to another

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3
Q

Carrier definition

A

A person who shows no symptoms when infected by a disease organism but can pass the disease to another individual

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4
Q

Disease reservoir definition

A

Where a pathogen is normally found; this may be humans or another animal and may be a source of infection

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5
Q

Endemic definition

A

A disease, which is always present at low levels in an area

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6
Q

Epidemic definition

A

Where there is a significant increase in the usual number of cases of a disease often associated with a rapid spread

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7
Q

Pandemic definition

A

An epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people

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8
Q

Vaccine definition

A

Uses non-pathogenic forms, products or antigens of micro-organisms to stimulate an immune response which confers protection against subsequent infection

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9
Q

Antibiotics definition

A

Substances produced by microorganisms which affect the growth of other microorganisms

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10
Q

Antibiotics resistance definition

A

Where a microorganism, which should be affected by an antibiotic, is no longer susceptible to it

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11
Q

Vector definition

A

A living organism which transfers a disease from one individual to another

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12
Q

Toxin definition

A

A chemical produced by a microorganism which causes damage to its host

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13
Q

Antigenic types definition

A

Organisms with the same or very similar antigens on the surface. Such types are sub groups or strains of a microbial species which may be used to trace infections. They are usually identified by using antibodies from serum

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14
Q

Points to consider about the statement the human body acts as a host to other living organisms

A

• Many organisms live in or on the human body
• can be in a symbiotic or parasitic relationships

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15
Q

Type of organism does cholera involve

A

Gram negative bacterium

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16
Q

Source of infection of cholera

A

Contaminated food or water

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17
Q

Tissue affected with cholera

A

Gut lining
• toxins affect gut lining so chloride channel proteins are affected and water and ions aren’t absorbed into blood
• patient has severe watery diarrhoea which leads to severe dehydration and frequently death

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18
Q

Mode of transmission of cholera

A

Water supplies
• humans act as reservoirs or carriers and contaminate water supplies
• only multiplies in the human host

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19
Q

Prevention of cholera

A

• treatment of water
• good hygiene
• provision of clean drinking water

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20
Q

Control methods and treatment of cholera

A

Antibiotics
Rehydration mainly

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21
Q

Vaccine of cholera

A

• temporary protection

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22
Q

Numbers of cholera in the world

A

Endemic is some areas

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23
Q

Type of organism in tuberculosis

A

Bacillus bacterium

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24
Q

Source of infection of tuberculosis

A

Inhalation of bacteria laden droplets from coughs and sneezes

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25
Q

Tissue affected with tuberculosis

A

Lungs and neck lymph nodes
• long term lung damage
• coughing, chest pain and coughing up blood

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26
Q

Mode of transmission of tuberculosis

A

Airborne droplets
• rapid spread in overcrowded places

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27
Q

Prevention of tuberculosis

A

• identifying people with active TB to stop spread

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28
Q

Control methods and treatment of tuberculosis

A

Long course of antibiotics
Vaccine

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29
Q

Vaccine of tuberculosis

A

BCG
given to children

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30
Q

Numbers of tuberculosis in the world

A

On the rise partly due to the link with the HIV epidemic

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31
Q

Type of organism with smallpox

A

Virus

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32
Q

Source of infection of smallpox

A

Inhalation/close contact with infected person

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33
Q

Tissue affected with smallpox

A

Blood vessels of skin, mouth and throat
• dispenses around the body
• fluid filled blisters, blindness and limb deformities

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34
Q

Mode of transmission of smallpox

A

Airborne/contact

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35
Q

Prevention of smallpox

A

Eradicated since 1980
• made deliberately extinct by humans

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36
Q

Control methods and treatment of smallpox

A

Before the vaccine - isolation to stop spread

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37
Q

Vaccine of smallpox

A

Successful immunisation program
• low rate of antigenic variation
• highly effective
• produces a strong immune response
• no animal resevoir

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38
Q

Type of organism of influenza

A

Virus
3 subgroups
Each with many different antigenic types

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39
Q

Source of infection of influenza

A

Inhalation of droplets from coughs and sneezes

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40
Q

Tissue affected by influenza

A

Cells lining upper respiratory tract
• causes sore throat, coughing and fever

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41
Q

Mode of transmission of influenza

A

Airborne droplets

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42
Q

Prevention of influenza

A

Regular hand washing
using and discarding tissues for coughs snd sneezes

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43
Q

Control methods and treatment of influenza

A

Quarantine and hygiene
Mode of transmission is difficult to control
Antibiotics are ineffective - used to treat symptoms of secondary bacterial infection

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44
Q

Vaccine of influenza

A

Annual vaccine
• surface antigens on virus change - need annual vaccine
• not always effective due to the number of different types

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45
Q

Type of organism of malaria

A

Protoctistan

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46
Q

Name of parasite of malaria

A

Plasmodium

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47
Q

Source of infection of malaria

A

Biting by mosquitoes

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48
Q

Tissue affected by malaria

A

Liver and red blood cells
• initially invades liver cells
• multiplies in rbc which burst
• when rbc burst they release more parasites and toxins which cause severe bouts of fever

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49
Q

Mode of transmission of malaria

A

Vector - female anopheles mosquitos
• feeds on blood which contains sexually reproducing stage of plasmodium
• infective stage migrates from gut of mosquito to salivary gland and therefore transmit parasite to new victim

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50
Q

Vector of malaria

A

Female anopheles mosquito

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51
Q

Prevention of malaria

A

Knowledge of mosquito and plasmodium life cycle required in order to exploit their weak points

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52
Q

Prevention measures used to prevent malaria responding to mosquito behaviour

A

• sleep under nets
• nets are treated with the pyrethroid insecticide
• drain or cover stagnant water
• film of oil on the water

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53
Q

Reason for effect of sleeping under nets to prevent malaria

A

Mosquitoes feed between dusk and dawn

54
Q

Reason for effect of treating nets with insecticide to prevent malaria

A

Kills mosquitoes

55
Q

Reason for effect of draining or covering stagnant water to prevent malaria

A

Removes mosquitoes access to egg-laying sites

56
Q

Reason for effect of making a film of oil on the water to prevent malaria

A

Lowered surface tension prevents larvae piercing surface to get oxygen

57
Q

What is a biological control

A

Use of a living species to control a pest

58
Q

Biological controls used to prevent malaria

A

• fish introduced into water
• infecting mosquitos with bacterium wolbachia
• male mosquitoes are sterilised with x-rays

59
Q

Reason for effect of introducing fish into water to prevent malaria

A

Larvae are aquatic so the fish eat them

60
Q

Reason for effect of infecting mosquitoes with bacterium wolbachia to prevent malaria

A

Wolbachia blocks plasmodium development in the mosquitoes

61
Q

Reason for effect of sterilising male mosquitoes with x-rays to prevent malaria

A

After they mate, no off-spring are reduced

62
Q

Control methods and treatment of malaria

A

•Drug treatments to mainly reduce chance of infection
•Resistance is an increasing problem
•Plasmodium is only affected by drugs outside the cells in the blood only - this limits effectiveness and there are side effects

63
Q

Vaccine of malaria

A

• difficult to develop due to mutations
• many antigenic types
• only effective when parasite is outside body cell - there is limited target stages

64
Q

What does it mean that viruses are intracellular parasites

A

They’re inert outside the host cell
They use a cell’s metabolic pathways to produce more virus paricles

65
Q

Lytic cycle

A

• immediately reproduce using host metabolism to copy their own nucleic acid and synthesise new protein coat
• immediate symptoms
• release may be by lysis or host cell (eg common cold) or budding (eg influenza)

66
Q

Lysogenic cycle

A

• integrate their nucleic acid into host cell genome - may stay there for many cell generations with no clinical effect
• enters lytic cycle at later time - symptoms are then produced
• eg herpes, HIV

67
Q

What is pathogenicity?

A

The ability of a pathogenic agent to cause disease

68
Q

Which ways can viruses be pathogenic?

A

• cell lysis
• toxins production
• cell transformation
• immune supression

69
Q

How can a virus be pathogenic through cell lysis

A

• bacteria - pressure of new virus particles inside cause bacteria to burst
• animal - inflammation caused by T-lymphocytes or antibodies cause lysis
• after cell lysis viruses escape to infect other cells/organisms

70
Q

How can a virus be pathogenic through toxin production

A

• many viral components and their by-products are toxic
• not fully understood

71
Q

How can a virus be pathogenic through cell transformation

A

• viral DNA can integrate into host chromosome
• if it inserts into a pro-oncogene/tumor suppressor gene which cab result in the cell undergoing rapid, uncontrolled division which can become cancerous

72
Q

How can a virus be pathogenic through immune suppression

A

• suppression of reactions that cause B and T lymphocytes to mature and so there’s a reduction in antibody formation
• reduction of phagocytic cells engulfing microbes
• eg HIV causes sufferes to be immune compromised - they’re very susceptible to infection

73
Q

Antibiotics

A

• produced by fungi
• act on bacteria
• dont act on viruses or eukaryotic cells due to absence of metabolic pathways
• treat bacterial infection without harm to patient

74
Q

What are the two mode of actions of antibiotics

A

Bactericidal and bacterisostatic

75
Q

Bactericidal mode of action of antibiotics

A

• kills the bacteria
• eg penicillin

76
Q

Bacteriostatic mode of action of antibiotics

A

• prevents growth but doesn’t cause death
• inhibits protein synthesis
• eg tetracycline

77
Q

Broad-spectrum antibiotics

A

• affect many different gram-positive and gram-negative species
• tetracycline and ampicillin

78
Q

Narrow-spectrum antibiotics

A

• more selective than broad spectrum
• eg penicillin G which only kills gram-positive bacteria

79
Q

Penicillin mode of action and spectrum

A

Bactericidal
Narrow spectrum

80
Q

Where penicillin produced from

A

The fungus Penicillium notatium

81
Q

How does penicillin kill bacterial cells

A

• affects formation of cross linkages in the peptidoglycan of the cell wall during growth and division of bacterial cells - binds to and inhibits the enzyme responsible for the formation of these cross-linkages
• this weakens the wall
• when osmotic changes occur and water enters the cells the cells lyse and die

82
Q

Which kind of bacteria is penicillin more effective against and why

A

Gram positive
Difference in cell wall structure

83
Q

Tetracycline mode of action and spectrum

A

Bacteriostatic
Broad spectrum

84
Q

Which fungus is tetracycline produced from

A

Streptomyces

85
Q

How does tetracycline inhibit the growth of bacterial cells

A

• affects protein synthesis which is a metabolic process common to all bacteria
• tetracycline diffuses and is pumped into bacteria cells
• acts as a competitive inhibitor of the 2nd anticodon binding site on the 30s subunit of bacterial ribosomes
• this prevents the binding of a tRNA molecule to it’s complementary codon
• inhibits the translation stage of protein synthesis

86
Q

What do bacteria do under optimum conditions and what does this result in

A

Divides rapidly
High mutation rate

87
Q

How can the overuse of antibiotics result in the spread of antibiotic resistance?

A

• some mutations confer antibiotic resistance so that these bacteria have a selective advantage in the presence of antibiotics - when they encounter antibiotic they’re not affected by it and continue to replicate whilst other non-mutated forms die
• overuse of antibiotics results in accidental selection of bacterial strains that are completely unaffected by some antibiotics

88
Q

What is the danger of the spread of antibiotic resistance among pathogenic bacteria

A

If they cause an infection it becomes increasingly difficult to control

89
Q

How is the skin a natural barrier?

A

• physical barrier
• collagen in connective tissue of dermis that is maintained by vitamin C- tough
• keratin in epidermal cells to make the skin waterproof

90
Q

How is skin microflora a natural barrier?

A

Offers protection by competing with pathogenic bacteria
• flora isn’t easily removed by washing unlike the bacteria

91
Q

How is ciliated mucous membranes a natural barrier?

A

• mucus trap microbes in inhaled air
• cilia brush/sweep the mucus away from the lungs

92
Q

How are tears, mucus and saliva natural barriers?

A

• contain lysozyme which is an enzyme that hydrolyses peptidoglycan in bacterial cell walls
• weakened cell wall breaks as water from tears and saliva enters microbe by osmosis which causes cells to lyse - killing the bacteria

93
Q

How is stomach acid a natural barrier?

A

Kills ingested bacteria in food and drink
pH 2

94
Q

If there is a breach of skin how do blood clots act as a natural barrier?

A

Seal wounds
Which prevents entry of microbes

95
Q

If there is a breach of skin how does inflammation act as a natural barrier?

A

• to localise breaks in the barrier
• there is increased blood flow to the area which brings a large number of phagocytic cells
• broken capillaries heal
• raised temperature as it is unfavourable to microbes and decreases their growth

96
Q

How does phagocytosis act as a natural barrier once skin has been breached?

A

They destroy invading microbes by engulfing and digesting them
Macrophages and neutrophiles

97
Q

Are natural barriers specific or non-specific responses to microbes

A

Non-specific

98
Q

Why are specific immune responses developed

A

As a result of antigens being recognised as foreign to the body

99
Q

What is produced following humoral response

A

Antibodies

100
Q

Which lymphocytes are involved in humoral response

A

B lymphocytes

101
Q

Where fo B lymphocytes originate and mature

A

Originate - stem cells in bone marrow
Mature - spleen and lymph nodes

102
Q

What do B lymphocytes contain to detect their specific antigens and what does this activation stimulate?

A

Each has receptors for the detection of its specific antigen
Activation stimulates the proliferation of B lymphocytes by mitotic division which differentiate to from plasma and memory cells

103
Q

What do plasma cells do during humoral response

A

Release antibodies

104
Q

What do memory cells do during immune response

A

Remain dormant in the circulation ready to divide if the same antigen is encountered again

105
Q

What are antibodies

A

• Proteins - globulins, quaternary
• Specific to the antigen which they bind to to form an antigen-antibody complex
• Y-shaped
• 4 polypeptide chains
• 2 binding sites

106
Q

Shape of antibody

A

Y shaped

107
Q

How many polypeptide chains and binding sites do antibodies have

A

4 polypeptide chains
2 binding sites

108
Q

What does the fact that antibodies have 2 binding sites mean

A

• 2 different antigens can be joined by 1 antibody
• hinge region is flexible so can bind to 2 antigens when they’re different distances apart
• allows for agglutination

109
Q

How does agglutination increase the rate of engulfment by phagocytes

A

If viruses or toxins are joined by agglutination then they’re too large to enter the cell

110
Q

What does the cell mediated response involve

A

Activation of T lymphocytes, phagocytic cells and B lymphocytes

111
Q

Where do T lymphocytes originate from and where are they activated

A

Originate - stem cells
Activated - thymus gland

112
Q

What causes the proliferation of T lymphocytes

A

Detection of the corresponding specific antigen

113
Q

What do macrophages do in initiate response when they come across a microbe

A

Engulf the microbes then display the antigens of the microbe on their cell surface
They’re antigen presenting cells

114
Q

What are the sub populations of T cells as T lymphocytes differentiate

A

T killer
T helper
T memory

115
Q

What do t killer cells do

A

Cause lysis of the target cells

116
Q

What do T memory cells do

A

Remain dormant in the circulation and then divide to form more T lymphocytes if the same antigen is encountered again in the future

117
Q

What do T helper cells do

A

• release cytokines which
- stimulate B lymphocytes to initiate antibody response
- stimulate phagocytosis by macrophages
- stimulate colonal expansion of B and T lymphocytes - mitosis results in a large population of cells specific to that particular antigen

118
Q

Explain primary immune response

A

• first exposure to a foreign antigen
• short latent period as macrophages carry out phagocytosis and incorporate the foreign antigen into their cell membrane
• t helper cells detect the antigens and secrete cytokines and stimulate B lymphocytes and macrophages
• B cells are activated and proliferate into plasma and memory cells
• low levels of antibody is secreted over 2-3 weeks as they clear the infection and symptoms disapear

119
Q

Explain secondary immune response

A

• re-exposure to same anitgen
• very short latent period due to memory cells
• very small amount of antigen is needed to stimulate rapid plasma cell production
• antibody levels increase to between 10 and 100 times greater than initial response in a very short time
• antibody levels stay high for longer
• no symptoms develop

120
Q

What is natural immunity and 2 examples

A

Immunity when no medical stimulation is involved
Catching the disease
Antibodies passed from mother to child

121
Q

What is artificial immunity and examples

A

Medical intervention’s used
Vaccination programmes or in transfusion of antibodies

122
Q

What is active immunity and examples

A

• when the individual produces antibodies
• long lasting protection due to production of memory cells
• natural - following infection
• artificial- following vaccination eg mmr

123
Q

What is passive immunity and examples

A

• individual receives antibodies produced by another individual
• short lived protection as antibodies are recognised as non-self and destroyed so no memory cells are produced
• natural - antibodies transferred by placenta or breast milk
• artificial- pre synthesised antibody is injected into individual eg tetanus antitoxin

124
Q

How do vaccines immunise people against disease eg rubella

A

Promotes a primary response without causing the disease as memory cells are produced
Active

125
Q

What kind of injection is used to provide passive, emergency treatment against infection eg rabies

A

• antibodies can be injected to provide rapid protection against a pathogen
• rabies - allows time for the person’s immune system to develop an active immune response
• also used with people with a primary immune deficiency disease eg HIV, AIDS, as patients dont make enough antibodies and cannot provide enough protection against pathogens

126
Q

What kind of antigenic variation will be more likely to be protected by a single round of immunisation and give example of infection that does this

A

Pathogens that exhibit no/low levels of it
Eg rubella

127
Q

What is needed with organisms with many antigenic types and mutate frequently and what is the problem , give example of infection

A

• repeated immunisation against most common antigens
• wont be 100% effective
Eg influenza

128
Q

What features do successful vaccines have

A

• they provoke a strong immune response- highly immunogenic and protect the individual from developing the disease
• they’ve little or no side effects that are mild in nature
• lead to long lasting immunity

129
Q

Describe concept of herd immunity

A

• if enough are immune to the disease through vaccination there is a reduced reservoir of the pathogen in the population
• it provides protection to people who ate unable to be vaccinated because of compromised immune systems or illness

130
Q

Which kind of ethical aspects should be taken into consideration when designing vaccination programmes?

A

• cost vs effectiveness
• protection of the individual compared to protection of the community
• rights of the individual when considering
- mandatory compared with voluntary
- side effects - are they real or perceived
- religious objections
- human rights

Wjec A Level Biology (13 decks)

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