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WJEC A2 Biology > Immunology & Disease- Unit 4A > Flashcards

Immunology & Disease- Unit 4A Flashcards

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1
Q

Define pathogen:

A

Organism which causes damage to a host

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2
Q

Define the term infectious:

A

Disease which can be passed from one organism to another

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3
Q

Define carrier:

A

Individual infected by microorganism with disease but show no symptoms. Can still pass o the disease.

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4
Q

What is a disease reservoir?

A

Long term host of a pathogen

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5
Q

What is an endemic?

A

Disease always present in an area at low levels

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6
Q

What is an epidemic?

A

Significant increase in usual number in cases of a disease

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7
Q

What is a pandemic?

A

Epidemic of infectious disease which has spread through multiple populations in multiple continents.

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8
Q

What is a vaccine?

A

Treatment stimulating immune response, giving protection against future infection. It provides active, acquired immunity.

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9
Q

What is an antibiotic?

A

Substance produced by microorganisms that affect growth of other microorganisms.

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10
Q

What is antibiotic resistance?

A

A microorganism is no longer affected by an antibiotic as it should be. It is no longer susceptible to it.

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11
Q

What is an antigenic type?

A

Subgroups/strains of microbial species that may be used to treat infection. Organisms with the same/similar antigens on their cell surface are classed as one group.

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12
Q

What is a vector?

A

An organism which transmits a disease to another organism

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13
Q

What is a toxin?

A

Chemical produced by a microorganism which causes damage to host

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14
Q

What is an antigen?

A

A substance which induces formation of antibodies/reacts with them when introduced into blood/tissue. They trigger an immune response as they are a foreign body.

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15
Q

What is an antibody?

A

Substance produced by lymphocytes in presence of specific antigen. They combine to neutralise/destroy the antigen.

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16
Q

E.coli is present in the large intestine, is this beneficial for humans or not?

A

Beneficial as the bacteria produce vitamin K.

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17
Q

What happens when E.coli is present in the stomach or small intestine?

A

Causes disease/infection

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18
Q

Why can taking antibiotics also be bad for you?

A

Kills harmful bacteria whilst killing the ‘good’ bacteria too, such as ones which prevent the build up of harmful microorganisms. There must be a balance maintained.

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19
Q

What are 5 ways a disease can be transmitted?

A

-Vectors
-Bodily fluids
-Water/food
-Air
-Direct contact

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20
Q

How is salmonella food poisoning spread?

A

Through uncooked meat of infected animals

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21
Q

How is cholera spread?

A

Faeces of infected individuals contaminating the water supply.

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22
Q

What is cholera caused by?

A

Vibrio cholera- gram negative bacteria

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23
Q

What is cholera considered to be in some countries?

A

Endemic

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24
Q

What tissue is affected by toxins produced by cholera?

A

Small intestine lining

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25
Q

What are the symptoms of cholera?

A

Watery diarrhoea, severe dehydration & possible death

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26
Q

How can cholera be prevented/treated? (4)

A

Sanitation of water supplies, safe sewage disposal, vaccination & antibiotics.

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27
Q

What is tuberculosis caused by?

A

Mycobacterium tuberculosis- gram negative/positive bacteria

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28
Q

What tissue is affected by tuberculosis?

A

Lymph nodes of neck & lungs

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29
Q

What are the symptoms of tuberculosis? (5)

A

-Chest pain
-Coughing up blood/sputum
-Swollen lymph nodes
-Loss of appetite
-Fever

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30
Q

How is tuberculosis spread?

A

-Airbourne so spread through droplets (cough/sneeze) inhaled.
Spreads rapidly in crowded areas.

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31
Q

How is tuberculosis prevented/treated?

A

BCG vaccination- prevention.
Antibiotics- treatment

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32
Q

What is smallpox caused by?

A

Variola major- DNA containing virus

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33
Q

What tissue is affected by smallpox?

A

Skin and multiple organs

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34
Q

What are the symptoms of smallpox?

A

-Rash
-Fluid-filled blisters
-Can cause blindness
-Can cause limb deformities

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35
Q

How is smallpox transmitted?

A

-Droplet & bodily fluids
Inhaled/in saliva/close contact

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36
Q

How is smallpox treated/prevented?

A

Vaccination has eradicated virus due to low rate of antigenic variation/mutation. It also lacks animal reservoirs

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37
Q

What is influenza caused by?

A

RNA containing virus consisting of 3 main subgroup with many different antigenic types, with many species being infected.

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38
Q

What tissue is affected by influenza?

A

Lining cells of the upper respiratory tract

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39
Q

Name the symptoms of influenza:

A

-Sore throat
-Cough
-Fever
-Shivering

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40
Q

How is influenza transmitted?

A

-Droplet transmission & contaminated surfaces
Inhaled from coughs/sneezes of infected

41
Q

How is influenza prevented/treated?

A

Quarantine & hygiene.
Antiviral drugs & vaccines are used but due to the large antigenic variation, they have a limited effect. Annual vaccines are required.

42
Q

What is malaria?

A

A major human disease caused by the parasite plasmodium. There are 5 species with many antigenic types.

43
Q

What role do female anopheles mosquito’s play within the spread of malaria?

A

Act as a secondary host and a vector, transmitting the disease when feeding on blood.

44
Q

What is malaria considered to be in different countries?

A

Endemic- some sub-tropical countries and can be epidemic in wet seasons.
Can sometimes be considered a pandemic.

45
Q

Describe the detailed steps involved in transmission of malaria: (8)

A
  1. Mosquito bites infected human.
    2.Red blood cells containing gametocytes of plasmodium enter mosquito.
  2. These fuse into gut of mosquito, producing sporozoites. (infected plasmodium)
  3. Sporozoites enter salivary gland of mosquito.
  4. Infected mosquito bites uninfected human, transmitting sporozoites to human with anticoagulant.
  5. Sporozoites move to liver, multiplying asexually to produce merozoites.
  6. Merozoites infect red blood cells, reproduce again , causing red blood cells to lyse, releasing parasites.
  7. This causes severe fluctuations of fevers over several days.
46
Q

How is malaria treated?

A

Drugs: Only effective when parasite is in blood, not inside cells.
-Quinine: used for long time, now less effective.
-Artemisinin: newer but parasite shows resistance.
-Combination: Artemisinin & others now used.

47
Q

How is malaria prevented?

A

-Use nets to prevent mosquitoes entering home.
-Wear protective clothing.
-Use insect repellents/insecticides.
-Drain areas of water where mosquitoes lay eggs.
-Use bacteria to infect mosquito larvae.
-Sterilise male mosquitoes.
-No current vaccine due to high antigenic variation & mutation

48
Q

Describe a virus:

A

-Cannot ‘live’ without a host.
-Consist of protein coat and strand of DNA/RNA.
-Enter a host cell & replicates using lysogenic or lytic cycle.

49
Q

Describe the lytic cycle:

A

-Virus reproduces using host cells metabolism to copy its own nucleic acid & make new protein coat using host’s amino acids.
-The virus cells are released via cell lysis or budding, in which they acquire an envelope from the host cells. (outer coat of plasma membrane)
-This then repeats.
An example is influenza

50
Q

What is the lysogenic cycle? Describe the steps:

A

-Virus integrates its nucleic acid into genome of host cells and then enters a dormant stage.
-It then enters the lytic cycle at a later stage.
An example is HIV.

51
Q

How do viruses cause disease?

A

-Cell lysis- release virus to infect cells.
-Production of toxins.
-Cell transformation- triggers cells to become cancerous.
-Suppression of immune systems that lead to: maturation of B and T lymphocytes and a reduction of antibody formation.

52
Q

What are the two ways antibiotics affect bacteria?

A

-Bacteriostatic: prevent bacteria multiplying so infection does not spread. Hosts immune system then kills the bacteria.
-Bactericidal: kills bacteria directly.

53
Q

Why do antibiotics not work on viruses?

A

Due to their lack of cell walls and metabolic pathways.

54
Q

Why do antibiotics not cause actual harm to the individual taking them?

A

Do not work on eukaryotic cells so cannot cause harm, but can kill ‘good’ bacteria within the body, lowering the microbial diversity.
They have selective toxicity.

55
Q

What are the two types of antibiotics which affect metabolic processes of bacteria?

A

Broad spectrum
Narrow spectrum

56
Q

What are broad spectrum antibiotics?

A

-Effective against broad spectrum of gram positive AND negative bacteria.
-Affect microbial process such as protein synthesis.
-An example is Ampicillin

57
Q

What are narrow spectrum antibiotics?

A

-More selective so affect LIMITED range of bacteria. (positive and negative)
-Affect specific processes like cell wall formation
-An example is penicillin.

58
Q

Describe gram positive bacteria:

A

-Thick layer of murein
-No layer of lipoprotein and lipopolysaccharide.
-Retain crystal violet dye
-More susceptible to penicillin & lysozymes

59
Q

Describe gram negative bacteria:

A

-Thin layer of murein
-Layer of lipoprotein & lipopolysaccharide, pretecting against penicillin and lysozymes.
-Do not retain crystal violet dye

60
Q

Describe penicillin and how it works:

A

-Narrow spectrum & bacericidal antibiotic
1. Diffuses through cell walls of gram positive bacteria, enters through SOME gram negative bacteria via porins.
2. Inhibits transpeptidase so it cannot catalyse the formation of cross links between murein and amino acid side chains in the cell wall.
3. This weakens the cell wall, causing inability to withstand changes in osmosis.
4. This leads to lysis of the bacteria cell.

61
Q

Describe tetracycline and how it works:

A

-Narrow spectrum & bacteriostatic antibiotic.
1. Inhibits protein synthesis in gram positive and negative bacteria by preventing translation by acting as a competitive inhibitor.

62
Q

What is antibiotic resistance and why does it occur?

A

Antibiotic resistance is the ability of a bacteria, to survive exposure to a substance with a dose that would usually destroy it.
Antibiotics have been used widely and often so bacteria has mutated to become resistant over time. These mutations are then passed on genetically when the bacteria reproduce, causing resistance.
An example is the ability to produce an enzyme which breaks down the antibiotic.

63
Q

What do physical barriers do?

A

Provide protection against pathogens entering the body.

64
Q

What do chemical and cellular responses do?

A

They are activated when physical barriers fail.

65
Q

What is a self antigen?

A

Induce formation of antibodies on surface of body cells

66
Q

What are non-self antigens?

A

Induce formation of antibodies on surface of foreign organism.

67
Q

Name some natural barriers: (innate immune system) (7)

A

-Skin/skin flora
-Ciliated epithelium & mucus
-Lysozymes
-Stomach acid
-Inflammation
-Clotting of blood
-Phagocytosis

68
Q

How do skin and connective tissues protect against infection? (3)

A

-Skin covers most of bodies surface.
-Collagen in connective tissue is tough so is a physical barrier.
-Keratin in epidermal cells provides waterproofing and secretes sebum containing fatty acids which have anti-microbial action.

69
Q

How does the skin’s natural flora prevent infection?

A

Natural populations of harmless bacteria/fungi live on skin with mucus membranes that inhibit growth of pathogens.
They can be destroyed by wide spectrum antibiotics.

70
Q

How does ciliated epithelium and mucus prevent infection?

A

Mucus traps microorganisms and cilia sweep the mucus from the lining of the upper respiratory tract to the throat where they can be swallowed. It then makes its way to the stomach to be dissolved by stomach acid.

71
Q

How do lysozymes and stomach acid prevent infection?

A

Lysozymes are present in tears, saliva and mucus. They kill bacteria by hydrolysing murein in bacterial cell walls.
Hydrochloric acid in the stomach kills any ingested microorganisms.

72
Q

How does blood clotting prevent infection?

A

Platelets clot to create a barrier (scab) for wounds to prevent bacteria/pathogens from entering.

73
Q

How does inflammation help infection? (4)

A

Damaged cells release chemicals making blood cells dilate and capillaries more leaky.
Blood rushes to site of infection, bringing phagocytes leaking out of capillaries.
The area become red, hot and swollen.
The high temperature is unfavourable for the microorganisms, causing some to be destroyed.

74
Q

How do phagocytes treat infection?

A

Brought to site of infection by inflammation.
They engulf and digest bacteria.
Infected cells also produce interferon, a chemical stopping the cell from making molecules that the pathogen needs.

75
Q

What are the 2 specific immune responses?

A

The humoral response
The cell mediated response

76
Q

Explain the humoral immune response:

A

If a B lymphocyte (B cell) meets an antigen with a complimentary bind/receptor site, it divided via mitosis. A clone is the made of (clonal expansion):
-Plasma cells which release antibodies for immediate use. These are short lived/term.
-Memory cells for future use. These are long lived/term. (a secondary immune response would occur if SAME antigen was introduced again)

77
Q

Where are B lymphocytes produced and where do they mature?

A

B lymphocytes (B cells) are derived from stem cells in bone marrow and mature in spleen and lymph nodes.

78
Q

How does inactivation of an antigen occur when an antibody binds to it? (4)

A

Agglutination.
-Each antibody can bind to 2 antigens, making microorganisms with antigens on their surface more susceptible to phagocytes as they clump together.
-The antibodies ‘tag’ the antigens, making them more recognisable to phagocytes.
-Antibodies neutralise the toxins.
-Antibodies prevent pathogens attaching to/entering host cells.

79
Q

Describe the cell mediated immune response:

A

-T lymphocytes (T cells) respond to antigen fragments presented by infected cells/phagocytic cells.
-In this response, they divide via mitosis and increase in size. (clonal expansion)
-each cloned T cell differentiates into 4 groups of specialised T cells. These carry out the rest of the cycle.

80
Q

Where are T lymphocytes produced and where are they activated?

A

Derived from stem cells in bone marrow and activated in thymus gland.

81
Q

What are T memory cells?

A

Remain in circulation and if the same antigen is encountered again, T cells are produced rapidly.

82
Q

What are killer T cells/cytotoxic T cells?

A

Combine with antigens on invading cells and cause death by lysis.

83
Q

What are T helper cells?

A

Help B cells produce antibodies. They also release cytokines which activate phagocytic cells to engulf pathogens.

84
Q

What are suppressor T cells?

A

Suppress other cells so that when antigens have been dealt with, antibody production stops.

85
Q

What is a primary immune response?

A

The first time being exposed to the infection/antigen being present.

86
Q

What is a secondary immune response?

A

Subsequent infection triggers it. Memory cells will rapidly produce antibodies for the recurring antigen.

87
Q

Explain the primary response in detail: (5)

A
  1. First exposure to antigen.
  2. Short latent period (delay) where antigen presentation occurs.
  3. Antigen detected by helper T cells, killer T cells are secreted to stimulate B cells and macrophages.
  4. B cells undergo clonal expansion, producing plasma cells secreting antibodies for 3 weeks, clearing the infection.
  5. Memory cells are also made and remain in circulation.
88
Q

What is antigen presentation?

A

Macrophages engulf foreign antigen, incorporating it into the cell membrane. The macrophage is now an antigen presenting cell.

89
Q

Explain the secondary response in detail: (4)

A
  1. Memory cells produced in primary response are triggered by subsequent encounter with same antigen.
  2. Memory cells undergo clonal expansion rapidly.
  3. Antibodies secreted much faster and in higher concentrations.
  4. High concentration is maintained for longer time, resulting in no symptoms.
90
Q

What are the 2 types of immunity?

A

Active and passive

91
Q

What is active immunity?

A

Lymphocytes activated by antigens on pathogen.
Antibodies and memory cells are made in response.

92
Q

What is passive immunity?

A

Individual becomes temporarily immune to antigen due to receiving ready made antibodies from somewhere else.

93
Q

What are the 2 sub-types of active immunity?

A

Natural and artificial

94
Q

What is natural active immunity?

A

T and B cells activated by antigens present on pathogen during NATURAL course of infection.
Antibodies and memory cells are made.

95
Q

What is artificial active immunity?

A

Injection of antigens into the body. (Vaccine)
T and B cells are activated.
Antibodies and memory cells made.

96
Q

In what ways are vaccination made?

A

Using:
-Weakened strains
-Inactive pathogens
-Isolated antigens
-Inactivated toxins

97
Q

What are the two sub-types of passive immunity?

A

Natural and artificial

98
Q

Describe natural passive immunity:

A

Pre-formed antibodies pass NATURALLY from mother to baby across placenta and through breast milk.
This is temporary until baby develops its own immune system.

99
Q

What is artificial passive immunity?

A

Pre-made antibodies

WJEC A2 Biology (12 decks)

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