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A Level Biology Year 1 > Chapter 5 - Cell recognition and the immune system > Flashcards

Chapter 5 - Cell recognition and the immune system Flashcards

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1
Q

What is an infection?

A

An interaction between the pathogen and the defence mechanisms of the body

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2
Q

What is an antigen?

A

A protein found on the cell surface of pathogens that generate an immune response

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3
Q

What is a pathogen?

A

A disease-causing microorganism

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4
Q

What is immunity?

A

When the body is well equipped against invasion from a pathogen so it doesn’t harm the individual

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5
Q

What must lymphocytes do before attacking an invader?

A

Distinguish between cells that belong to the individual and cells that don’t

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6
Q

What are the four things that the immune system can identify?

A

Pathogens, non-self material, toxins and abnormal body cells

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7
Q

Why can the immune system be a problem when receiving organ donations?

A

The antigens are recognised as non-self, so without immunosuppressants, the immune system would try and attack it

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8
Q

What is a non-specific response?

A

The response is immediate and the same for all pathogens

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9
Q

What is a specific response?

A

The response is slower and specific to each pathogen

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10
Q

Two types of non-specific response

A

Physical barriers and phagocytosis

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11
Q

Two types of specific response

A

Cell-mediated response and humoral response

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12
Q

How many types of lymphocyte are there?

A

10 million

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13
Q

How do lymphocytes recognise cells belonging to the body?

A

In the womb, lymphocytes are constantly colliding with the body cells of the fetus
Some lymphocytes will have sites that are complementary to these cells
These will either die or be suppressed
The remaining lymphocytes are those that are complementary to non-self material that the fetus hasn’t yet been exposed to
In adults, the same process happens in the bone marrow, producing only lymphocytes that will be able to fight an infection

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14
Q

What are the two types of white blood cell?

A

Phagocyte and lymphocyte

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15
Q

Process of phagocytosis

A

A phagocyte recognises foreign antigens on the pathogen
Receptors on the phagocyte bind to the pathogen
They engulf the pathogen, forming a phagosome
Lysosomes fuse with the phagosome
Lysozymes hydrolyse the cell walls of the bacteria, breaking it down
The phagocyte presents the antigens of the pathogen on its surface

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16
Q

What are the two types of lymphocyte?

A

B lymphocyte

T lymohocyte

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17
Q

Where do B lymphocytes mature?

A

Bone marrow

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18
Q

Where do T lymphocytes mature?

A

Thymus gland

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19
Q

What type of immunity are B cells associated with?

A

Humoral

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20
Q

What type of immunity are T cells associated with?

A

Cell-mediated

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21
Q

What are antigen presenting cells?

A

Cells that can present foreign antigens on their surface

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22
Q

How do T cells recognise cells to destroy?

A

They display foreign antigens

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23
Q

How do T cells help to destroy pathogens?

A

Receptors on the T helper cells are complementary to the antigens presented on the surface of phagocytes
This attachment stimulates the T cell to divide rapidly by mitosis, forming cloned cells
These cells can do one of four things

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24
Q

What are the four things that can happen to T cells after they have been cloned?

A

a) memory cells
b) stimulate phagocytes for phagocytosis
c) stimulate B cells
d) activate cytotoxic t cells

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25
Q

How do cytotoxic T cells kill cells?

A

They produce a protein called perforin, which creates holes in the cell surface membrane so the cell loses control of what enters and leaves and the cell dies

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26
Q

What is humoral response?

A

Response to infection using antibodies

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27
Q

What is clonal selection?

A

Each B cell has a differently shaped active site, which is complementary to only one antigen. When the body is infected with the pathogen with this antigen, the B cell engulfs it and displays the antigen. TH cells bind to this displayed antigen and stimulate the B cell to divide by mitosis

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28
Q

What is the name of the process by which B cells display a foreign antigen on their cell surface?

A

Endocytosis

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29
Q

When B cells are cloned, what are the two things they can turn into?

A

Memory cells, or plasma cells

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30
Q

What type of cell is responsible for the primary defence?

A

Plasma cells

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31
Q

What do plasma cells do?

A

They bind to the antigen to form an antibody-antigen complex

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32
Q

How do plasma cells kill pathogens?

A

Antibodies have two binding sites, meaning they can bind to multiple pathogens at once. This causes them to clump together (agglutination) so phagocytes recognise and destroy them

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33
Q

How do memory cells help to kill pathogens?

A

They coordinate the secondary response - when you are infected again, they divide rapidly to produce plasma cells (which secrete antibodies) and more memory cells so there is less chance of you becoming ill

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34
Q

Why is the primary immune response so slow?

A

There aren’t many B cells that can secrete the antibody needed to fight the pathogen

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35
Q

What happens during the primary immune response?

A

You show signs of the disease - it takes time for the necessary B cells to be made. Then, memory cells are made, which make the secondary response faster

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36
Q

Why do you often show no symptoms of a disease after being infected a second time?

A

Clonal selection happens faster, so the right B cells and antibodies are created quicker and the immune system gets rid of any pathogens before you show symptoms

37
Q

How many polypeptide chains are antibodies made from?

A

4 - two heavy and two light

38
Q

What is the binding site on each antibody called and why?

A

The variable region - it differs between all antibodies so they are specific to just one antigen

39
Q

What are the two ways in which antibodies can help to destroy cells?

A

Agglutination - clumping that pathogens together

They act as markers which stimulate the phagocytes to attack the pathogen

40
Q

What are monoclonal antibodies?

A

Antibodies produced from a single group of genetically identical B cells

41
Q

Why do antibodies have unique binding sites?

A

They have unique tertiary structures

42
Q

What are the two ways in which monoclonal antibodies can help cure cancer?

A

1) Antibodies with a complementary shape to the tumour markers on the cancer cells are produced. They attach to the cells and block the chemical signals that stimulate tumour growth
2) Anti-cancer drugs are attached to the antibodies. When they bind to the antigens on the tumour, they release these chemicals which destroy the cells

43
Q

How are monoclonal antibodies used to diagnose certain cancers?

A

With some cancers, a higher level of a certain protein will be present. Monoclonal antibodies that interact with this protein are given to the person and highlight the increased levels

44
Q

How are monoclonal antibodies used in pregnancy test kits?

A

Mothers produce hCG when they’re pregnant
The application area of the stick contains antibodies for hCG which are attached to a blue dye
If hCG is present, it will bind with the antibodies, forming a complex, and move up the strip and carry the blue dye with it
At the test strip, there are immobilised antibodies. Any hCG will bind with these antibodies and the blue dye will show up in a solid line

45
Q

3 ethical concerns with monoclonal antibodies

A

Making mice produce tumour cells involves deliberately giving them cancer
There have been deaths associated with monoclonal antibodies treating MS
In one experiment, six healthy volunteers suffered organ failure

46
Q

How are monoclonal antibodies produced?

A

A mouse is exposed to the disease
The B cells in the mouse make antibodies, which are extracted
These cells are mixed with tumour cells
Detergent breaks down the cell membranes so the two can fuse together, forming a hybridoma
The hybridoma cells are separated and cloned
Successful clones are produced on a large scale

47
Q

What is passive immunity?

A

The type of immunity you get from being given antibodies by a different organism

48
Q

Why is passive immunity only temporary?

A

No memory cells are formed

49
Q

What is active immunity?

A

The body is stimulated by an antigen into producing its own antibodies

50
Q

What is natural active immunity?

A

An individual is infected with a disease under normal circumstances

51
Q

What is artificial active immunity?

A

Inducing an immune response in an individual without them getting the disease

52
Q

Which type of immunity means you have to be exposed to an antigen?

A

Active

53
Q

Which type of immunity gives you immediate protection?

A

Passive

54
Q

Which type of immunity produced memory cells?

A

Active

55
Q

Which type of immunity is long lasting?

A

The antibody, as well as memory cells, are produced by the body after infection

56
Q

4 features of a successful vaccination programme

A

The vaccine must be cheap and widely available
There must be minimum side effects
It must be possible to achieve herd immunity
There must be appropriate means of administering it

57
Q

Why are vaccines so good?

A

They allow you to build up memory cells to a disease without suffering from it

58
Q

Why are booster vaccines given?

A

To make sure that sufficient memory cells are produced

59
Q

Why are vaccines not given orally? 2

A

It may be broken down by enzymes in the gut

It could be too large to be absorbed into the blood

60
Q

What is herd immunity?

A

When such a large proportion of a population has been vaccinated against a pathogen, it makes it difficult to spread

61
Q

Why is herd immunity important?

A

It is never possible to vaccinate all people in a population against a disease

62
Q

Why might vaccination be ineffective? (4)

A

Antigenic variability
Certain pathogens can ‘hide’ from the vaccine
There may be too many strains of a pathogen to vaccinate against them all
People with defective immune systems won’t be effective

63
Q

What is antigenic variation?

A

Some pathogens can change the antigens on their surface, so the antibodies in our bodies aren’t effective against them any more. Memory cells of our previous vaccination won’t recognise these antigens as foreign so we will be infected again

64
Q

Ethical issues with vaccines 4

A

The use of animals for testing
Testing on volunteers can lead to unnecessary illness
Some people think that it is unfair that those who don’t want the vaccine because they are afraid of side effects are still protected by herd immunity
If there was an epidemic of a disease, there would be difficult decisions to make about who would receive the vaccine

65
Q

Which disease was the MMR vaccine linked to?

A

Autism

66
Q

What is an antibody?

A

A protein produced by a B cell in response to the complementary antigen

67
Q

What are cytokines?

A

Chemicals secreted by T helper cells to activate B cells

68
Q

Ethical issues with monoclonal antibodies

A

Animals are purposefully given cancer to produce the tumour cells needed

69
Q

Flaws with the research suggesting MMR vaccine leads to autism

A

The sample size was just 12 children

The bias of medical companies conducting it

70
Q

What can HIV lead to?

A

AIDS

71
Q

What is AIDS?

A

The immune system weakens and eventually fails so the victim is more susceptible to infections

72
Q

How does HIV cause symptoms of AIDS?

A

It infects and eventually kills the helper T cells
These cells are what stimulate phagocytes, cytotoxic T cells and B cells
Without T cells, the body can’t fight infection and so you become very ill

73
Q

When do people with HIV develop AIDS?

A

When the helper T cells in their body reach critically low levels

74
Q

What is enclosed in the capsid of an HIV cell?

A

The genetic material (RNA) and enzymes (reverse transcriptase)

75
Q

What is the capsid made from?

A

Protein

76
Q

What does reverse transcriptase do?

A

It turns the RNA in the viral cell into DNA in the host cell

77
Q

How does HIV replicate?

A

HIV enters the body and circulates around the bloodstream
The attachment proteins bind to CD4 proteins found on the surface of T helper cells
The capsid fuses with the cell surface membrane, releasing the genetic material and enzyme into the cell
Once there, reverse transcriptase converts the virus’ RNA into DNA
The DNA moves into the nucleus of the T helper cell
Once there, the DNA makes mRNA using the cell’s enzymes
This contains the instructions for making new viral proteins and RNA
The mRNA leaves the nucleus through a pore and uses the cells protein synthesis mechanisms to make HIV particles
A piece of the T helper cell’s cell membrane surrounds the particles and they break away, forming new viruses

78
Q

What are the initial symptoms of AIDS?

A

Infections of mucous membranes, e.g. nose, ears and genitals

79
Q

Factors that affect the progression of HIV to AIDS

A

Existing infections
Strain of HIV
Access to healthcare

80
Q

What happens during the late stages of HIV?

A

The patients can develop a variety of serious infections, like fungal infections of the respiratory system, which ultimately kill the patient

81
Q

What drugs are given to slow down the progression of HIV?

A

Antiviral drugs

82
Q

How can HIV be spread from person to person? (3)

A

Unprotected sex
Infected bodily fluids
From mother to fetus

83
Q

How do antibiotics kill bacteria?

A

Bacteria cells are surrounded by a cell wall, made of a protein called murein
As water enters the cell by osmosis, the cell stretches against the wall
The murein is inelastic and so stops more water from moving into the cell
Antibiotics stop the production of murein, which weakens the cell walls. When water moves into cells with these weak walls, they burst

84
Q

Why don’t antibiotics kill viruses?

A

They have no cell wall made of murein that the antibiotic could destroy

85
Q

What does the ELISA test do?

A

Uses antibodies and antigens to see if a patient has a surprising number of antigens or antibodies

86
Q

How does the ELISA test work?

A

Apply the sample to a surface
Wash to remove any unattached antigens
Add the antibody that is specific to the antigen
Leave the two to bind together
Wash the surface again to remove any excess antibodies
Add a secondary antibody attached to an enzyme, which can bind with the first antibody
Add the colourless substrate of the enzyme
The enzyme will act upon the substrate to turn it coloured
The amount of the antigen present is relative to the intensity of the end colour observed

87
Q

How are antibodies produced?

A
  1. virus contains antigen;
  2. virus engulfed by phagocyte/macrophage;
  3. presents antigen to B-cell;
  4. memory cells/B-cell becomes activated;
  5. (divides to) form clones;
  6. by mitosis;
  7. plasma cells produce antibodies;
  8. antibodies specific to antigen;
  9. correct reference to T-cells/ cytokines;
88
Q

What are cytokines?

A

Chemicals produced by T cells which stimulate B cells to divide by mitosis

89
Q

Describe how the presentation of a virus antigen leads to the secretion of an antibody
against this virus antigen

A
  1. Helper T cell/TH cell binds to the antigen (on
    the antigen-presenting cell/phagocyte);
  2. This helper T/TH cell stimulates a specific B
    cell;
  3. B cell clones
    OR
    B cell divides by mitosis;
  4. (Forms) plasma cells that release antibodies;

A Level Biology Year 1 (21 decks)

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