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AS Biology > Module 4.1 - Disease and the Immune System > Flashcards

Module 4.1 - Disease and the Immune System Flashcards

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1
Q

What is a disease?

A

A condition that impairs the normal functioning of an organism.

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2
Q

What are the 4 types of pathogen?

A

Bacteria, virus, fungi and protocista.

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3
Q

What is a communicable disease?

A

A disease that can be spread between organisms.

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4
Q

Give three examples of diseases caused by bacterium and what organisms they affect?

A

> Tuberculosis - affects animals, typically humans and cattle.
Bacterial meningitis - affects humans.
Ring rot - affects potatoes and tomatoes.

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5
Q

Give three examples of diseases caused by a virus and what organisms they affect?

A

> HIV/ AIDS - affects humans.
Influenza - affects animals including humans.
Tobacco mosaic virus - affects plants.

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6
Q

Give two examples of diseases caused by a fungus and what organisms they affect?

A

> Black sigatoka - affects banana plants.
Ringworm - affects cattle.
Athlete’s foot - affects humans.

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7
Q

Give three examples of diseases caused by a protocista and what organisms they affect?

A

> Potato/tomato blight - affects potatoes and tomatoes.

>Malaria - Animals, including humans.

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8
Q

What is direct transmission?

A

When a disease is transmitted directly from one organism to another.

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9
Q

Give some examples of direct transmission?

A

> Droplet infection (coughing or sneezing tiny droplets of mucus or saliva directly onto someone).
Sexual intercourse.
Touching an infected organism.

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10
Q

What is indirect transmission?

A

Indirect transmission is when a disease is transmitted from one organism to another via an intermediate. Intermediates include air, water, food or another organism (known as a vector).

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11
Q

Give an example of how potato/tomato blight uses indirect transmission?

A

Spread when spores are carried between plants - first in the air and then in water.

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12
Q

What are 3 factors that can affect the transmission of many communicable diseases?

A

> How crowded people are, how close proximity they live to each other.
Climate.
Social factors - healthcare, health education.

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13
Q

Why is potato/tomato blight especially common during wet summers?

A

The spores need water to spread.

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14
Q

What are animals physical barriers that prevent infection?

A

> Skin - physical barrier, chemical barrier produces chemicals that are antimicrobial and can lower pH, inhibiting the growth of the pathogens.
Mucous membranes - Protects body openings that are exposed to the environment, secrete mucus that tarps pathogens and contains antimicrobial enzymes.
Blood clotting - Plug wounds to prevent pathogen entry and blood loss.
Inflammation - Causes swelling helping to isolate any pathogens. Causes vasodilation which increases blood flow to the affected area and brings white blood cells to the area to fight of any pathogens that may be present.
Wound repair - Re-form a barrier against pathogen entry.
Expulsive reflexes - Expel foreign objects including pathogens from the body. Happen automatically.

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15
Q

What is a blood clot?

A

A mesh of protein (fibrin) fibres.

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16
Q

How is a blood clot formed?

A

Formed by a series of chemical reactions that take place when platelets (fragments of cells in the blood) are exposed to damaged blood vessels.

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17
Q

What triggers inflammation?

A

Can be triggered by tissue damage - the damaged tissue releases molecules which increases the permeability of blood vessels, so they start to leak fluid into the surrounding area.

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18
Q

What are the signs of inflammation?

A

Swelling, pain, heat and redness.

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19
Q

How does wound repair happen?

A

The surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound. The tissue below the wound then contracts to bring the edges of the wound closer together. It is repaired using collagen fibres - too many collagen fibres and you’ll end up with a scar.

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20
Q

Describe the expulsive reflex of a sneeze?

A

When the mucous membranes in the nostrils are irritated by things such as dust or dirt.

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21
Q

Describe the expulsive reflex of a cough?

A

A cough stems from irritation in the respiratory tract.

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22
Q

Describe the physical defences plants have against pathogens?

A

> Waxy cuticle - physical barrier, stops water collecting reducing risk of infection by pathogens that are transferred between plants in water.
Cell walls - physical barrier for pathogens that get past the waxy cuticle.
Produce a polysaccharide callose - Deposited between plant cell walls and plasma membranes during times of stress. Callose deposition makes it harder for pathogens to enter cells and at the plasmodesmata may limit the spread of viruses between cells.

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23
Q

Describe the chemical defences plants have against pathogens?

A

> Can produce antimicrobial chemicals which kill pathogens or inhibit their growth.
Other chemicals secreted by plants are toxic to insects - reduces the amount of insect feeding on plants and reduces the risk of infection by plant viruses carried byt insect vectors.

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24
Q

Give 2 examples of chemicals plants produces as a part of their defence against pathogens?

A

> Saponins - destroy cell membranes of fungi and other pathogens.
Phytoalexins - Inhibit growth of fungi and other pathogens.

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25
Q

What are antigens?

A

Antigens are molecules (usually proteins/polysaccharides) found on the surface of cells.

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26
Q

What are antigen’s purpose?

A

When a pathogen invades the body, the antigens on its cell surface are identified as foreign, which activates cells in the immune system.

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27
Q

The immune response involves specific and non-specific stages, what is the specific immune response?

A

The specific response is antigen-specific - it is aimed at specific pathogens. It involves white blood cells called T and B lymphocytes.

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28
Q

What is involved in the non-specific stage of the immune response?

A

Happens in the same way for all microorganisms - whatever foreign antigens they have.

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29
Q

Describe the process of phagocytosis (the 1rst stage in the immune response)?

A

1) A phagocyte is recognises the antigens on a foreign pathogen.
2) The cytoplasm of the phagocyte moves round the pathogen, engulfing it. This may be made easier by the presence of opsonins.
3) The pathogen is now contained in a phagosome in the cytoplasm of the phagocyte.
4) A lysosome fuses with the phagosome. The enzymes in the lysosome break down the pathogen.
5) The phagocyte then presents the pathogen’s antigens. It sticks the antigens on its surface to activate other immune system cells. When a pathogen does this it is acting as an antigen-presenting cell (APC).

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30
Q

What are opsonins and what are their function?

A

Opsonins are molecules in the blood that attach to foreign antigens to aid phagocytosis.

31
Q

What is a phagosome?

A

A type of vesicle.

32
Q

What are the first white blood cells that are involved in the immune response and what do they do?

A

Neutrophils are the first white blood cells to respond to a pathogen inside the body. Neutrophils move towards a wound in response to signals from cytokines.

33
Q

What are cytokines?

A

Proteins that act as messenger molecules and are released by cells at the site of the wound.

34
Q

What is the second stage of the immune response and what happens?

A

Phagocytes activate T lymphocytes -

1) T lymphocyte’s surface is covered with receptors which bind to antigens presented by APCs.
2) Each T lymphocyte has a different receptor on its surface so when it meets a complimentary antigen, it binds to it - so each T lymphocyte will bind to a different antigen.
3) This activates the T lymphocyte - this process is called clonal selection.
4) Clonal expansion is where it divides to produce clones of itself and different types of lymphocytes carry out different functions.

35
Q

What is a T lymphocyte?

A

Another type of white blood cell.

36
Q

There are multiple different types of activated T lymphocytes. Give some examples?

A

T helper cell, T killer cell, T regulatory cell and some become memory cells.

37
Q

What is a T helper cell’s role?

A

They release substances to activate B lymphocytes and T killer cells.

38
Q

What is a T killer cell’s role?

A

These attach to and kill cells that are infected with a virus.

39
Q

What is a T regulatory cell’s role?

A

These suppress the immune response from other white blood cells. This helps to stop immune system cells from mistakenly attacking the host’s body cells.

40
Q

What is the third stage of the immune response?

A

When T lymphocytes activate B lymphocytes (another type of white blood cell), which divide into plasma cells.

41
Q

Describe the process of when T lymphocytes activate B lymphocytes, which divide into plasma cells?

A

1) B lymphocyte (white blood cell) is covered with proteins called antibodies.
2) Antibodies bind to antigens to form an antigen-antibody complex.
3) Each B lymphocyte has a different shaped antibody on it’s surface.
4) When the antibody on the surface of a B lymphocyte meets a complementary shaped antigen, it binds to it and so each B lymphocyte will bind to a different antigen.
5) This, together with substances released from T helper cells, activates the B lymphocyte. This process is another example of clonal selection.
6) The activated B lymphocyte divides by mitosis, into plasma cells and memory cells - this is an example of clonal expansion.

42
Q

Describe how cell signalling works?

A

A cell may release (or present) a substance that binds to the receptors on another cell - this causes a response of some kind in the other cell.

43
Q

Why is cell signalling important in the immune response?

A

It helps to activate all the different types of white blood cells that are needed.

44
Q

Give an example of cell signalling in the immune response?

A

T helper cells release interleukins (a type of cytokine) that bind to receptors on B lymphocytes. This activates the B lymphocyte (signal the B lymphocytes that there’s a pathogen in the body).

45
Q

What is the final stage in the immune response?

A

Plasma cells make more antibodies to a specific antigen.

46
Q

Describe the process of antibodies being produced?

A

1) Plasma cells are clones of the B lymphocytes (they’re identical to the B lymphocytes).
2) They secrete loads of the antibody, specific to the antigen, into the blood.
3) These antibodies will bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes.

47
Q

Describe the structure of the antigen-antibody complex?

A

> The variable regions of the antibody form the antigen binding site.
The shape of the variable region is complementary to a particular antigen. The variable regions differ between antibodies.
The hinge region allows flexibility when the antibody binds to the antigen.
The constant regions allow binding to receptors on immune system cells (e.g. phagocytes). The constant region is the same in all antibodies.
Disulphide bridges (a type of bond) hold the polypeptide chains of the protein together.

48
Q

Give 3 examples of how antibodies help to clear an infection?

A

> Agglutinating pathogens.
Neutralising toxins.
Preventing the pathogen binding to human cells.

49
Q

Describe how agglutinating pathogens work?

A

Each antibody has two binding sites, so an antibody can bind to two pathogens at the same time - the pathogens become clumped together. Phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once. Antibodies that behave in this way are known as agglutinins.

50
Q

Describe how neutralising toxins work?

A

Like antigens, toxins have different shapes. Antibodies called anti-toxins can bind to the toxins produced by pathogens. This prevents the toxins from affecting human cells, so the toxins are neutralised (inactivated). The toxin-antibody complexes are also phagocytose.

51
Q

Describe what happens when antibodies prevent the pathogen binding to human cells?

A

When antibodies bind to the antigens on pathogens, they may block the cell surface receptors that the pathogens need to bind to the host cells. This means the pathogen can’t attach to or infect host cells.

52
Q

Describe the primary response and why it’s slow?

A

1) When a pathogen enters the body for the first time, the antigens on it’s surface activate the immune system. This is called the primary response.
2) The primary response is slow for there aren’t many B lymphocytes that can make the antibody needed to bind to it.
3) The body will produce enough of the right antibody to overcome the infection and the infected person will show symptoms of the disease.
4) After being exposed to an antigen, both T and B lymphocytes produce memory cells and these remain in the body for a long rime.
5) Memory T lymphocytes remember the specific antigen and will recognise it 2nd time round and record the specific antibodies needed to bind to the antigen.
6) The person is now immune and their immune system has the ability to quickly respond to a 2nd infection.

53
Q

Describe what happens in the secondary response?

A

1) If the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response - the secondary response.
2) Clonal selection happens faster. Memory B lymphocytes activated and divide into plasma cells that produce the right antibody to the antigen. Memory T lymphocytes are activated and divide into the correct type of T lymphocytes to kill the cell carrying the antigen.
3) The secondary response often gets rid of the pathogen before you show any symptoms.

54
Q

What differs in the cells being activated in the primary and secondary response?

A

Primary - B and T lymphocytes.

Secondary - Memory cells.

55
Q

What is active immunity?

A

Where your immune system makes its own antibodies after being stimulated by an antigen.

56
Q

What is natural active immunity?

A

This is when you become immune after catching a disease.

57
Q

What is artificial active immunity?

A

This is when you become immune after you’ve been given a vaccination containing a harmless dose of antigen.

58
Q

What is passive immunity?

A

This is the type of immunity you get from being given antibodies made by a different organism and your immune system doesn’t produce any antibodies of its own.

59
Q

What is natural passive immunity?

A

This is when a baby becomes immune due to the antibodies it receives from its mother, through the placenta and breast milk.

60
Q

What is artificial passive immunity?

A

This is when you become immune after being injected with antibodies from someone else.

61
Q

Describe the differences between active and passive immunity?

A 
Active - 
>Requires exposure to antigen.
>Takes a while for protection to develop.
>Protection is long term.
>Memory cells are produced.
Passive -
>No exposure to antigen.
>Protection is immediate.
>Protection is short-term.
>Memory cells aren't produced.
62
Q

Describe what happens in an abnormal immune response with someone who has an autoimmune response?

A

An organism’s immune system isn’t able to recognise self-antigens (antigens present on their own cells). The immune system treats the self-antigens as foreign antigens and launches an immune response against the organism’s tissues.

63
Q

Give two examples of autoimmune diseases?

A

> Lupus - caused by the immune system attacking cells in the connective tissues. This damages the tissues and causes painful inflammations. It can affect the skin and joints, as well as organs such as the heart and lungs.
Rheumatoid arthritis - Caused by the immune system attacking cells in the joints. Again this causes pain and inflammation.

64
Q

What are vaccinations?

A

Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. This means you become immune without getting any symptoms.

65
Q

What is herd immunity?

A

If the majority of people in community are vaccinated, the disease becomes extremely rare. This means that even people who haven’t been are unlikely to get the disease because there’s no one to catch it from.

66
Q

What do vaccines help prevent?

A

Epidemics.

67
Q

Describe how vaccines and vaccination programs change?

A

The influenza vaccine changes every year for the antigens on the surface of the influenza virus change regularly, forming new strains of the virus.

68
Q

What are antibiotics?

A

Chemicals that kill or inhibit the growth of bacteria.

69
Q

How do some strains of bacteria become antibiotic resistant?

A

When there is genetic variation in a population of bacteria and have a mutation that is naturally resistant to the antibiotic.

70
Q

Why is it helpful for bacteria to be antibiotic resistant?

A

They are better able to survive, even in a host who’s being treated with antibiotics to get rid of the infection for they live for longer and reproduce more in the space. This leads to the allele for antibiotic resistance being passes on to lots of offspring (this is an example of natural selection).

71
Q

Give two examples of antibiotic resistant bacteria?

A

> MRSA - causes serious wound infections and is resistant to several antibiotics.
Clostridium difficile - infects the digestive system.

72
Q

What are ways that scientists and doctors are trying to overcome antibiotic resistance?

A

> Developing new antibiotics
Modifying existing ones.
Doctors are encouraged to reduce their use of antibiotics (not for minor infections).
Patients are advised to take the whole course of antibiotics to make sure their infection is fully cleared.

73
Q

What possible sources of medecine need to be protected and why?

A

> Natural compounds found in plants, animals and microorganisms that are manufactured into medicinal drugs.
Only small proportion of organisms have been investigated and its possible that other plants or microorganisms exist that contain compounds that could be used to treat currently incurable diseases.
Possible sources of drugs need to be protected by maintaining biodiversity.
New techniques that could be invented could make already investigated organisms useful.

74
Q

Describe two future ideas in medecine?

A

> Personalised medecine - tailored to an individuals DNA, can study the relationship between someones genetic information and responsiveness to drugs and prescribe drugs best for you.
Synthetic biology - Design things like artificial proteins, cells and microorganisms.

AS Biology (12 decks)

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