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Biology > Unit 2 - Cell Immunity > Flashcards

Unit 2 - Cell Immunity Flashcards

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1
Q

Describe what the immune system is able to identify through the specific molecules located on the cell surface.

A
  • Pathogens
  • Abnormal body cells
  • Toxins
  • Cells from other organisms of the same species
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2
Q

Define what is meant by an antigen.

A
  • Cell surface molecule which stimulates an immune response
  • Enables identification of
    Pathogens
    Abnormal body cells
    Toxins
    Cells from other organisms of the same species
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3
Q

Describe the effect of antigen variability on disease

and disease prevention.

A
  • Pathogen’s DNA mutates frequently resulting in the new shape of antigens made due to different primary structure
  • Therefore memory cells are no longer complementary to anitigen
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4
Q

Describe the process of phagocytosis

A
  • Phagocyte moves towards pathogen via chemotaxis and surrounds pathogen as recognises foreign antigen
  • Phagocyte cytoplasm engulfs the pathogen into vacuole to form a phagosome
  • Phagosome and Lysosome fuse and release digestive enzymes lysozymes
  • Which hydrolyse/digest the pathogen/bacteria
  • Antigens displayed on the cell membrane
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5
Q

Describe what is meant by an antigen-presenting cell

A
  • A macrophage that displays antigen from the pathogen on its surface/cell membrane
  • This allows for recognition from T-cells
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6
Q

Describe the cell-mediated response.

A
  1. Once the pathogen is destroyed, antigens presented on its cell membrane(APC)
  2. Complementary T-lymphocyte binds to foreign antigen on APC
  3. Activating T-lymphocyte, therefore, produces clones of complementary T helper cell by mitosis
  4. Cloned complementary T-helper cells then stimulate:
    =cytotoxic T- cells
    =B-cells (humoral response)
    =Phagocytes for phagocytosis
    OR become memory cells
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7
Q

Describe the humoral response.

A
  1. Antigen binds to the complementary antibody on membrane of the B-cell to form antigen-antibody complex
  2. Antigen enters the B-cell by endocytosis so B-cell becomes an APC
  3. Activated complementary T-cell binds to the B-cell causing B-cell to undergo clonal expansion
  4. B-cells reproduce by mitosis & differentiate into plasma cells OR MEMORY cells
    - Plasma cells secrete antibodies with the complementary variable region to antigen
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8
Q

Define an antibody

A
  • A protein secreted by plasma cells

- Quarternary structure protein

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9
Q

Describe the structure of an antibody

A

(2 heavy chains)
(2 light chains held by disulfide bridges to connect polypeptide chains)
- Binding sites on the variable region have specific tertiary structure complementary to an antigen
- Rest of the molecule known as the constant region

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10
Q

How do antibodies lead to the destruction of a pathogen?

A
  • Antigen-antibody complex is formed
  • Which leads to the destruction of pathogens through agglutination
  • Which enhances phagocytosis
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11
Q

Describe the role of a memory cell.

A
  • Specialised T-helper cell/Memory B -cell
  • Remain in low levels in the blood
  • Which can divide rapidly by mitosis & differentiate if encounters the same pathogen before symptoms occur
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12
Q

Describe the difference between the primary and secondary immune response.

A

In secondary response:

  • Faster rate of antibody production compared to primary so antibody levels remain higher
  • Pathogen usually destroyed before any symptoms
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13
Q

Describe the difference between passive and active immunity.

A

(faster)
PASSIVE - No exposure to antigen, Involves antibodies
Natural - Antibodies in breast milk
Artificial - Needle stick injections

ACTIVE - Requires exposure to antigen, Involves antibodies
Natural - Immune response after disease
Artifical - Vaccination

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14
Q

Describe the process of vaccination.

A
  • Inactive/Dead form of pathogen/antigen injected into body
  • Triggers primary immune response where B cells undergo clonal expansion
  • Memory cells are produced which can differentiate into plasma cells which make complementary antibodies to anitgen
  • Memory cells remain in bloodstream and differentite ino plasma cells which rapidly produce antibodies so secondary response is rapid
  • Higher concentration of antibodies in blood therefore antigens destroys pathogen before the symptoms
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15
Q

Describe the concept of herd immunity.

A
  • Vaccinating large proportions of the population reduces available carriers of pathogens
  • Which protects those who are not vaccinated
    e. g People with a weak immune system
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16
Q

Describe the structure of HIV.

A
  • Genetic material RNA and enzyme reverse transcriptase surrounded by protein capsid at the core
  • Phospholipid viral envelope
  • GP120 attachment proteins on the surface
17
Q

Describe how HIV replicates in a T Helper cell

A
  • Attachment proteins on virus bind to the complementary CD4 receptor on T Helper cells
  • HIV protein capsule fuses with TH cell enabling RNA & enzymes to enter
  • HIV enzyme reverse transcriptase copies viral RNA into DNA copy and moves it to the TH cell nucleus
  • mRNA transcribed and TH cell creates viral proteins and viral proteins released from cell
18
Q

Describe how HIV leads to aids.

A
  • Attachment proteins on virus bind to the complementary CD4 receptor on T Helper cells
  • HIV particles replicate in TH cells causing them to be destroyed
  • AIDS develops when there are too few T Helper cells for the immune system to function
  • Individuals cannot destroy other pathogens or secondary infections
19
Q

Describe why antibiotics are ineffective against viruses.

A
  • Antibiotics work by damaging murein cell walls but viruses have no cell walls
  • Viruses replicated inside host cells so difficult to destroy without damaging normal body cells
20
Q

Define a monoclonal antibody

A

Antibodies produced from a single clone of B cells

21
Q

Describe the importance of monoclonal antibodies in targeting medication to specific cell types.

A
  • Targeted treatment by antibodies being attached to therapeutic drugs & carrying drugs to specific cells
22
Q

Describe the importance of monoclonal antibodies in medical diagnosis.

A

Pregnancy tests

  • Detecting HCG hormone in the urine of women
  • Any HCG hormone binds to antibodies on beads to form an antigen-antibody complex
  • Which causes test trip to turn blue if pregnant as antibodies with HCG are immobilised
23
Q

Describe the importance of monoclonal antibodies in the ELISA test.

A
  • Antigens bind to the bottom of the test plate
  • First antibody complementary in shape to the antigen binds to antigen to form antigen-antibody complexes
  • Second antibody with enzyme attached added to bind to the first antibody
  • Solution/substrate added and colour changes if positive
24
Q

Describe ethical issues of the use of vaccines and monoclonal antibodies.

A

VACCINES
Animal rights issues - some people disagree animals should be used in this way as may cause harm
Potentially dangerous side effects with humans being tested

MONOCLONAL ANTIBODIES
Animal rights issues - some people disagree animals should be used in this way

Biology (30 decks)

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