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Biology > 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 two forms does a lymphocyte have

A
  • Cell- mediated response using T lymphocytes
  • humoral response involving B lymphocytes
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2
Q

How can lymphocytes distinguish between self cells and non-self cells

A

-every type of cell has specific molecules on their surface
- it is the proteins on the surface of cells because of their highly specific tertiary structure which allow the immune system to identify one cell from another

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3
Q

What is clonal selection and what does it explain

A

-clonal selection is when an infection occurs, complementary proteins to those of the pathogen are stimulated to divide to build up numbers to destroy the pathogen

  • clonal selection explains why there is a time lag between exposure to the pathogen and body’s defences bringing it back under control
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4
Q

Name and describe the two types of white blood cell

A
  1. phagocytes- ingest and destroy pathogens by a process called phagocytosis before it can cause harm
  2. lymphocytes- involved in the immune responses
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5
Q

Process of phagocytosis

A
  1. chemical products of pathogens act as attractants causing phagocytes to move towards pathogens
  2. phagocytes have receptors on the cell surface membrane which recognise and attach to chemicals of the pathogen
  3. they engulf the pathogen to form a vesicle known as a phagosome
  4. lysosomes move towards the vesicle and fuse with it
  5. lysozymes destroy ingested bacteria by hydrolysis
  6. soluble products of the broken down pathogen are absorbed into the cytoplasm of the phagocyte
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6
Q

Definition of immunity

A

the ability of organisms to resist infection against by protecting against disease-causing microorganisms or their toxins that invade the body

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7
Q

Definition of an antigen

A

any part of an organism or substance that is recognised as non-self by the immune system and stimulates an immune response

the presence of an antigen triggers the production of an antibody as part of the body’s defence

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8
Q

Describe where lymphocytes are produced and what their role is

A
  • lymphocytes are produced by stem cells in the bone marrow
  • the role is to provide long-term immunity for the body
  • they are specific to pathogens
  • they are slower at first
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9
Q

Name and describe the two types of lymphocyte

A
  1. B lymphocyte:
    - mature in the bone marrow
    - associated with the humoral immunity- immunity involving antibodies that are present in body fluids
  2. T lymphocyte:
    - mature in the thymus gland
    - involved in cell-mediated immunity- immunity involving body cells
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10
Q

What is cell mediated immunity

A
  • immune response that does not involve antibodies
  • activation of phagocytes, antigen-specific T lymphocytes and the release of various cytokines in response to an antigen
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11
Q

Role of cell mediated immunity

A

for the destruction of infected cells by cytotoxic T cells, or destruction of intracellular pathogens by macrophages

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12
Q

What is the cellular response

A

where T lymphocytes will only respond to antigens that are present on a body cell

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13
Q

How do cytotoxic T cells kill infected cells

A
  • they produce a protein called perforin
  • the perforin makes holes in the cell surface membrane
  • making the antigen become freely permeable to all substances and the cell dies as a result
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14
Q

Explain humoral immunity

A
  • involves antibodies
  • many types of B cell can produce a specific antibody that is complementary to an antigen so therefore the antibody attaches to the complementary antigen
  • antibody enters B cell by endocytosis and gets presented on its surface
  • T helper cells bind to the processed antigens and stimulate the B cell to divide by mitosis to form a clone of B cells with the complementary antibody to the antigen
  • this is called clonal selection and accounts for the ability to rapidly respond to any antigen
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15
Q

What are clones of an antibody referred to as

A

monoclonal antibodies

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16
Q

What types of cell can monoclonal antibodies form

A
  1. plasma cells
    - secrete antibodies
    - responsible for the immediate defence of the body against infection
    - responsible for the primary response of creating antibodies and memory cells
  2. memory cells
    - responsible for the secondary immune response
    - memory cells live considerably longer
    - they can divide rapidly and produce plasma cells if they experience the same antigen later
    - tend to work before the individual gets symptoms
17
Q

Describe an antibody

A
  • proteins with a specific binding sites synthesised by B cells
  • specific antibodies reacts with an antigen because they have complementary binding sites
18
Q

Structure of antibodies

A
  • 4 polypeptide chains
  • the chains of one pair are long and called heavy chains
  • the chains of the other pair are short and called light chains
  • each antigen has a specific binding site which precisely fits onto an antigen to form an antigen- antibody complex
  • the binding sites on different antibodies are different so are called the variable region
  • the rest of the antibody is the same on all antibodies so is called the constant region
19
Q

How can antibodies lead to destruction of antigens

A
  • they can cause agglutination of bacterial cells making it easier for phagocytes to locate them
  • can serve as markers which stimulate phagocytes to engulf the bacterial cells to which they are attached
20
Q

Define and describe passive immunity

A
  • no direct contact with the pathogen or its antigen is necessary to induce immunity and immunity can be acquired immediately
  • passive immunity doesn’t produce antibodies so there is no lasting immunity
21
Q

Define and describe active immunity

A
  • stimulating the production of antibodies of the individuals own immune system and direct contact with the pathogen is necessary
  • although immunity takes time to develop it is longer lasting than passive immunity
22
Q

Name and describe the two types of active immunity

A
  1. natural active immunity- results from an individual becoming infected with a disease under normal circumstances, the body produces its own antibodies
  2. artificial active immunity- forms the basis of vaccination, involving inducing an immune response in an individual without them suffering the symptoms of a disease
23
Q

Describe vaccination

A
  • the introduction of the appropriate disease antigens into the body either by injection or by mouth
  • intention is to stimulate an immune response against the disease
24
Q

What is the vaccine part of a vaccination

A
  • is the material part which contain one or more parts of antigen form the pathogen
  • produces a slight response because only a small amount of antigen is introduced but crucially memory cells are then produced
  • the memory cells stay in the blood and allow for a greater and quicker response to the same pathogens entering the body
25
Q

What is herd immunity

A

when a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread within the population

26
Q

Structure of HIV

A
  • lipid envelope with attachment proteins on
  • inside is a protein layer called the capsid which encloses two single strands of RNA and some enzymes
  • an enzyme in HIV is reverse transcriptase which catalyses the production of DNA from RNA
27
Q

How does HIV cause AIDS

A
  • it attacks helper T cells
  • causes AIDS by killing or interfering with normal functioning of helper T cells
  • without sufficient number of helper T cells, immune system cant stimulate B cells to produce antibodies
    HIV doesn’t kill directly but its the weakened immune system which if infected cant cope eventually leading to death
28
Q

What is the ELISA test

A
  • enzyme linked immunosorbent assay
  • uses antibodies to detect the presence of protein in a sample but also the quantity
  • extremely sensitive and can pick up even very small traces of a protein
29
Q

procedure for ELISA TEST

A
  • apply a sample to a surface to which all the antigens will attach
  • wash the surface to remove unattached antigens
    -add a complementary antibody
  • wash the surface to remove any excess antibody
  • add a second antibody which binds to the first antibody
  • add the colourless substrate of the enzyme
  • the amount of antigen present is relative to the intensity of the colour that develops
30
Q

Why are antibiotics ineffective against viral diseases

A
  • there are no metabolic mechanisms or cell structures for them to disrupt
  • viruses have a protein coat rather than a murein cell wall and so don’t have the sites where antibiotics can work

Biology (10 decks)

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