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AS Biology > 2C - The immune system > Flashcards

2C - The immune system Flashcards

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1
Q

What are antigens?

A

Molecules (usually proteins) that can generate an immune response when detected by the body.

Any part of an organism (often a protein of the surface of a cell) that is recognised as foreign by our immune system.

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2
Q

What can antigens generate?

A

An immune response when detected by the body.

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3
Q

Where are antigens found?

A

On the surface of cells.

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4
Q

What are antigens used by?

A

The immune system

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5
Q

How/why does the immune system use antigens?

A

To identify pathogens, abnormal body cells, toxins and cells from other individuals of the same species.

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6
Q

How are antigens controlled and what does this mean?

A

Genetically controlled - close relatives have more similar antigens.

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7
Q

What are the 2 immune systems?

A

Specific and non-specific.

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8
Q

Who/what has a non-specific immune system?

A

All animals

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9
Q

Who/what has a specific immune system?

A

Only vertebrates.

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10
Q

What are examples of non-specific immune systems?

A

Phagocytosis by phagocytes.

Physical barriers.

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11
Q

What is the response like for the non-specific immune system?

A

Immediate and the same for all pathogens.

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12
Q

What are examples of specific immune systems?

A

T and B lymphocytes.

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13
Q

What is the response like for the specific immune system?

A

Slower and specific to each pathogen.

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14
Q

What type of immune system (response) are physical barriers?

A

Non-specific

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15
Q

What type of immune system (response) is phagocytosis by phagocytes?

A

Non-specific

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16
Q

What type of immune system (response) are B and T lymphocytes?

A

Specific

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17
Q

What are the barriers the body has to infection?

A

Skin
Hydrochloric acid
Epithelial mucus

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18
Q

How does the skin act as a barrier to infection?

A

Physical barrier that pathogens find it difficult to penetrate.

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19
Q

How does hydrochloric acid act as a barrier to infection?

A

Denatures the enzymes or coat proteins of most pathogens that enter the stomach.

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20
Q

How does epithelial mucus act as a barrier to infection?

A

Epithelial layers inside the body produce mucus that pathogens stick to and become immobilised.

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21
Q

What is the phagosome?

A

Where the vesicle transports the pathogen to and where the pathogen is broken down in the phagocyte.

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22
Q

What are lysozymes?

A

The enzymes found in lysosomes that break down the pathogen when fused to the phagosome.

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23
Q

What are the parts to a phagocyte?

A 
Phagosome
lysosome (& lysozymes)
Nucleus
Cell membrane
Vesicles
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24
Q

Why are T-lymphocytes called that?

A

T because they mature in the thymus gland.

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25
Q

What are T-lymphocytes used in?

A

Cell-mediated immunity.

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26
Q

What has to be present for cell-mediated immunity?

A

The pathogen.

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27
Q

What to T-lymphocytes have on each cell?

A

Receptor proteins.

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28
Q

What can the receptor proteins on each T-lymphocyte do?

A

Detect one specific antigen.

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29
Q

Approximately how many types of T-cell are there?

A

100000000

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30
Q

What do each different type of T-cell do?

A

Display different receptors.

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31
Q

What forms do T-cells occur in?

A

Helper T-cells (Th cells)

Cytotoxic T-cells (Tc cells)

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32
Q

What happens when a phagocyte destroys a pathogen?

A

It presents the pathogens antigens on its outer membrane (antigen-presenting cell).

33
Q

What cells have antigens on their surface?

A

Cancerous cells and non-self cells.

34
Q

What are non-self cells?

A

Not cells that normally occur in our body e.g. viruses.

35
Q

What are the 2 immune responses?

A

Cell-mediated immunity and humoral immunity.

36
Q

Explain what happens in cell-mediated immunity:

A
  1. Pathogens invade body cells or are taken in by phagocytes.
  2. The phagocyte places antigens from the pathogen on its cell-surface membrane.
  3. Receptors on the specific helper T cell (TH cell) fit exactly onto these antigens.
  4. This attachment activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells.
  5. The cloned T cells:
    a - develop into memory cells that enable a rapid
    response to future infections by the same
    pathogen.
    b - stimulate phagocytes to engulf pathogens by
    phagocytosis.
    c - stimulate B cells to divide and secrete their
    antibody.
    d - activate cytotoxic T cells (TC cells).
37
Q

How do lymphocytes recognise cells belonging to the body?

A
  • 10 million lymphocytes in body at once capable of recognising chemical shape.
  • In the fetus they are constantly colliding with each other.
  • These will therefore collide more exclusively with self-cells.
  • They fit the body cells and the die or become suppressed.
  • Remaining lymphocytes are the ones that might fight non-self cells and therefore only respond to foreign material.
38
Q

What are the 2 types of WBC?

A

Phagocytes and lymphocytes.

39
Q

What process to phagocytes carry out?

A

Phagocytosis.

40
Q

Where are phagocytes found?

A

Travel in the blood but can move out of the blood vessels and into other tissues.

41
Q

Describe the process of phagocytosis:

A
  • Chemical products of pathogen or dead/damaged cells act as attractants, causing phagocytes to move towards the pathogen.
  • Phagocytes receptors recognise and attach to chemicals on the surface of the pathogen.
  • They engulf the pathogen to form a vesicle known as phagosome.
  • Lysosomes move towards the vesicle and fuse with it.
  • Lysozymes destroy pathogen by hydrolysis of their cell walls.
  • The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte.
42
Q

How to cytotoxic T cells kill infected cells?

A

Produce the perforin protein which makes holes in the cell-surface membrane meaning that it becomes freely permeable to all substances and a result, the cell dies.

43
Q

Why is the action of T cells most effective against viruses?

A

Because they replicate inside cells and this sacrifice of a body cell prevents viruses from multiplying and infecting more cells.

44
Q

Is humoral immunity active or passive?

A

Active

45
Q

Why is humoral immunity active?

A

Because it uses antibodies dissolved in tissue fluid or plasma.

46
Q

How do antigens enter the B cell?

A

Endocytosis.

47
Q

What is endocytosis?

A

The process by which antigens enter the B cell.

48
Q

What is clonal selection?

A

When B cells it activated to divide by mitosis to produce B cell clones (plasma cells).

49
Q

What is it called when B cells are activated to divide by mitosis to produce B cell clones?

A

Clonal selection

50
Q

What is the function of plasma cells?

A

Secrete antibodies into blood plasma leading to the destruction of an antigen.

51
Q

In what immune response are plasma cells and antibodies produced?

A

Primary immune response.

52
Q

In what immune response are memory cells produced?

A

Secondary immune response.

53
Q

What do memory cells do?

A

Don’t produce antibodies directly but circulate in the blood and tissue fluid. When they encounter the same pathogen at a later date, they divide rapidly and develop into plasma cells and more memory cells.

54
Q

Do memory cells produce long term or short term immunity?

A

Long term

55
Q

What type of immunity are B cells associated with?

A

Humoral immunity.

56
Q

Describe the process of humoral immunity:

A

1- B cell with complementary antibody engulfs pathogen.
2- B cell presents antigen (antigen-presenting cell).
3- T cell binds to presented antigen using its complementary receptor protein.
4- Activates B cell to divide.

AND THEN EITHER:

5- Plasma cell clones made to secrete antibodies (primary response).
6- Attach to antigens and; agglutinate (stick cells to target), stop pathogens invading body cells or bind to free toxin proteins.

OR:

7- Memory cells made and circulate in blood for future infections (secondary response).

57
Q

What are antibodies?

A

Proteins with specific binding sites synthesised by B cells.

58
Q

What type of lymphocytes are associated with antibodies?

A

B-cells

59
Q

Describe the structure of an antibody:

A

Composed of 4 polypeptide chains (2 heavy chains and 2 light chains).
Chains joined by disulphide bonds.
Form a Y shaped structure.
Stem = constant region.
Ends of the arms = variable regions that bind to the antigen.

60
Q

What do the variable regions of an antibody do?

A

Bind to antigens.

61
Q

What part of the antibody binds to the antigen?

A

Variable regions.

62
Q

What protein structure does an antibody have?

A

Quaternary structure as it has multiple polypeptide chains.

63
Q

What are the long chains on an antibody called?

A

The heavy chains.

64
Q

What are the short chains on an antibody called?

A

The light chains.

65
Q

What is formed when an antibody binds to an antigen?

A

An antigen-antibody complex.

66
Q

What does the constant region on an antibody do?

A

Binds to receptors on cells such as B cells.

67
Q

What do antibodies do?

A

Prepare antigen for destruction.

68
Q

In what 2 ways to antibodies assist antigen destruction?

A
  • Cause agglutination of bacterial cells making it easier for phagocytes to locate and engulf them.
  • Serve as markers that stimulate phagocytosis to engulf the bacterial cells to which they are attached.
69
Q

All antibodies have the same…

A

…constant region.

70
Q

What is the speed like of the primary immune response?

A

Slow

71
Q

Why is the primary immune response slow?

A

Because there aren’t many B-cells that can make the antibody needed to bind to the antigens.

72
Q

Will a person show symptoms in a primary immune response?

A

Yes

73
Q

What happens after being exposed to an antigen?

A

Both T and B cells produce memory cells which circulate in the blood for a long time. Memory T cells remember the specific antigen and will recognise it a second time round. Memory B cells record the specific antibodies needed to bind to the antigen.

74
Q

What does the term immune mean?

A

The immune system has the ability to respond quickly to a second infection.

75
Q

How fast is the secondary immune response compared to the primary immune response?

A

Much quicker and much stronger.

76
Q

Why is the secondary immune response quicker and stronger?

A

Clonal selection happens faster. Memory B cells are activated and divide into plasma cells which produce the right antibody to the antigen. Memory T cells are activated and divide into the correct type of T cells to kill the cell carrying the antigen.

77
Q

What will each antigen induce?

A

A different B cell to multiply and form a clone of itself.

78
Q

What will each clone of a B cell do?

A

Produce a different antibody.

AS Biology (47 decks)

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