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Biology > 2.4 - The immune system > Flashcards

2.4 - The immune system Flashcards

1
Q

What do specific molecules (proteins) on the cell surface enable the immune system to identify which can stimulate an immune response?

A
  • pathogens
  • cells from other organisms of the same species e.g from transplant
  • abnormal body (cancer/tumour) cells
  • toxins
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2
Q

What are some physical barriers to infection?

A
  • skin (tough physical barrier)
  • stomach acid (kills bacteria)
  • gut and skin flora (competes with pathogens)
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3
Q

What are some examples of non-specific immune responses?

A
  • inflammation
  • lysozyme action
  • interferon
  • phagocytosis
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4
Q

Define antigen

A

foreign protein that stimulates an immune response

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5
Q

How does antigen variability affect disease and disease prevention?

A
  • mutation in DNA (or viral RNA if virus)
  • antigens (or attachment proteins if virus) altered
    so:
  • for bacteria etc: antibodies no longer complementary to antigen = vaccines no longer effective so increased disease spread
  • for virus: attachment protein can bind to receptors of other species etc.
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6
Q

Describe the process of phagocytosis

A
  • phagosome fuses with lysosome
  • virus digested by lysozymes
  • antigen from virus displayed on cell-surface membrane (phagocyte becomes an antigen-presenting cell)
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7
Q

Where are T and B cells produced and where do they mature?

A

both produced in bone marrow
B mature in bone marrow and T mature in thymus gland

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8
Q

Describe the cellular response (T-lymphocytes)

A

foreign antigens presented by phagocytes bind to specific receptors on cell surface of T cells, which activates them

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9
Q

What do helper T cells stimulate?

A
  • cytotoxic T cells
  • more helper T cells
  • B cells
  • phagocytes
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10
Q

Describe the response of B lymphocytes to a foreign antigen in the humoral response

A
  • B cell binds to specific complementary receptor/antigen (clonal selection)
  • B cell engulfs and digests antigen then becomes an antigen presenting cell which attracts T-cell
  • T-cell secretes cytokines and B cell divides by mitosis and mature into plasma cells
  • plasma cells produce monoclonal antibodies
  • plasma cells -> memory cells
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11
Q

Define antibody

A

a protein specific to an antigen produced by B cells

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12
Q

Draw a labelled diagram of the structure of an antibody

A
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13
Q

How is an antigen destroyed?

A

formation of antigen-antibody complex which leads to agglutination and phagocytosis of bacterial cells

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14
Q

What response are plasma cells involved in?

A

primary immune response

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15
Q

What response are memory cells involved in?

A

secondary immune response

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16
Q

What is herd immunity?

A

a large proportion of a population are vaccinated against a disease which prevents the disease spreading to unvaccinated individuals

17
Q

What are vaccines?

A

introducing small quantities of dead/inactive pathogen into the body to stimulate a primary immune response

18
Q

Describe the differences between active and passive immunity

A
  • active involves memory cells, passive doesn’t
  • active involves production of antibody by plasma cells
  • passive involves antibody introduced into body from outside source
  • active is long term because antibody produced in response to antigen
  • passive is short term as antibody is broken down
  • active can take time to develop, passive is fast acting
19
Q

Draw the structure of the human immunodeficiency virus (HIV)

A
  • lipid envelope with embedded attachment proteins
  • inside protein capsid is RNA and reverse transcriptase
20
Q

How does HIV cause the symptoms of AIDS?

A
  • after infection of T helper cell, T helper cell is killed
  • HIV spreads so more are killed, which weakens the immune system
21
Q

Why are antibiotics ineffective against viruses? What are viruses treated with instead?

A
  • antibiotics target the cell wall so bacterial cell cannot control entry and exit of water and will burst
  • viruses have a capsid coating as they are acellular (no cell wall)
  • viruses are treated with antiretroviral drugs
22
Q

Define monoclonal antibody

A

antibody produced from a single clone of a specific B-cell

23
Q

What are monoclonal antibodies are used for?

A
  • medical diagnosis
  • targeting medication to specific cell types by attaching a therapeutic drug to an antibody
  • pregnancy testing
24
Q

Explain the ethical issues associated with the use of vaccines and monoclonal antibodies

A
  • some thing animal testing is unethical
  • risks of vaccine must be balanced with benefits
  • must be tested in humans first to determine toxicity
  • very expensive
  • should they be compulsory
25
Q

Describe the ELISA test

A
  • 1st antibody binds to antigen
  • 2nd antibody with enzyme attached is added
  • 2nd antibody binds to antigen
  • substrate added and colour changes
26
Q

Give two ways in which pathogens can cause disease

A
  • bacteria release toxins
  • kill tissues/cells
27
Q

Describe how a virus is replicated

A
  • attachment proteins attach to receptors on helper T cell
  • RNA enters cell
  • reverse transcriptase converts RNA to DNA
  • DNA inserted into helper T cell
  • DNA transcribed into viral mRNA
  • viral mRNA translated into new viral proteins
  • viral particles assembled and released
28
Q

What is the process of antibodies clumping cells together so phagocytes can find them more easily?

A

agglutination

29
Q

What is natural active immunity?

A

arises from exposure to an antigen/getting disease

30
Q

What is natural passive immunity?

A

baby receives antibodies from mother through placenta

31
Q

What is artificial active immunity?

A

acquired through vaccinations which stimulate immune system and antibodies produced

32
Q

What is artificial passive immunity?

A

antibodies are injected into body

33
Q

Secondary immune response compared to primary

A

antibodies produced in higher concentration and quickly

Biology (38 decks)

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