AQA AS Biology > Immunity > Flashcards

Immunity Flashcards

(60 cards)

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1
Q

What is the process of phagocytosis?

A

Engulfing of pathogens

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2
Q

Define pathogen

A

An organisms that causes disease in another organism

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3
Q

What are the methods used by antibodies to get rid of/kill pathogens?

A
  • Labelling the pathogen for phagocytosis- Neutralisation of toxins- Agglutination of pathogens
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4
Q

Define monoclonal antibodies

A

Antibodies produced from a single group of genetically identical B plasma cells

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5
Q

What are the methods the body uses to prevent the entry of pathogens?

A
  • Mucus- Stomach acid- Enzymes
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6
Q

In phagocytosis, whar is the last thing done by the macrophage?

A

Presents the antigens of the pathogen on its membrane

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7
Q

What are the methods in which pathogens cause disease

A
  • Rupturing them to release nutrients- Breaking down nutrients within cells- Replicating inside of cells and bursting them when released
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8
Q

How are pathogens able to cause disease?

A

Release toxins

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9
Q

What do antibodies consist of?

A

Protein

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10
Q

A protein or polysaccharide found on the surface of cells that stimulates the production of antibodies is also known as?

A

An antigen

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11
Q

What is an antigen?

A

A protein on the surface of cells which causes an immune response

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12
Q

What do antigens allow the immune system to recognise?

A
  • Pathogens- Cells from organisms of the same species- Abnormal body cells e.g. tumors- Toxins
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13
Q

What is a pathogen?

A

An organism that causes disease e.g. Bacteria/Fungi/Viruses

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14
Q

What do pathogens do?

A
  • Destroy host cells- Produce toxins
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15
Q

What makes up the immune response?

A
  • Phagocytosis- T-cells- B-cells- Plasma cells
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16
Q

What are examples of cellular immune responses?

A
  • Phagocytosis- T-cells
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17
Q

What are examples of humoral immune responses?

A
  • B-cells- Plasma cells
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18
Q

What does a humoral response involve?

A
  • Antibodies- Clonal selection- Monoclonal antibodies
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19
Q

What is phagocytosis?

A
  • First line of defence- General immune response
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20
Q

How is phagocytosis carried out?

A
  • Phagocyte identifies foreign antigen- Phagocyte engulfs pathogen into its phagocytic vacuole- Lysosomes fuse with the phagocytic vacuole and release lysosomes which hydrolyse the pathogen- Phagocyte (antigen presenting cell) presents the antigens of the pathogen on its membrane which activates T-cells
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21
Q

How are T-lymphocytes activated?

A

By antigens presented on phagocytes

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22
Q

What are the two types of T-lymphocyte?

A
  • T-helper cells- Cytotoxic T-cells
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23
Q

What do T-helper cells do?

A

Activate B-cells and cytotoxic T-cells

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24
Q

What do cytotoxic T-cells do?

A

Kill pathogens (cellular response)

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25
What are antibodies?
Proteins that bind to antigens to kill pathogens
26
What do B-cells do?
Undergo clonal selection
27
What is clonal selection?
The B-cell with the complimentary antibody to the pathogens antigen (and can therefore form an antigen-antibody complex) is selected and divides into many copies called plasma cells
28
What are plasma cells?
Clones of the selected B-cell with the complimentary antibody to the pathogens antigen
29
What do plasma cells do?
- Make monoclonal antibodies (that can form an antibody-antigen complex with pathogens antigen)- Monoclonal antibodies can then stick pathogens together (agglutination) so phagocytes can engulf many pathogens at once
30
What happens to plasma cells post infection?
Some plasma cells are saved as memory B-cells which are reactivated If there is a secondary response
31
What is the structure of an antibody?
- Antibodies are proteins with a specific primary, secondary and tertiary structure- Antibodies have a variable region and a constant region which are joined by a hinge and held together by disulphide bridges- The antibodies tertiary structure is responsible for the specific variable region which allows the antibody to form antibody-antigen complexes with its complementary antigen
32
What happens in the primary immune response?
- First immune response- Slow because immune response has to under go phagocytosis -> T-cells -> B-cells -> plasma cells and then the production of antibodies - Whilst the immune response is taking place the pathogen is able to multiply and you feel symptoms - When infection is over you save some plasma cells as memory cells incase of a secondary infection
33
What happens in a secondary immune response?
- The same pathogen with the same antigen infects you- The immune response is faster and stronger because you already have the memory B and T-cells which can divide and carry out the humeral and cellular responses in order to kill pathogens (T) and produce antibodies (B) - Because the pathogen has less time to replicate you fell no symptoms - Antigenic variation and various pathogen strains can prevent this
34
What are monoclonal antibodies?
Identical antibodies made from the same B-cell/plasma cell
35
How are monoclonal antibodies used in targeting medication?
- Monoclonal antibodies used to deliver drugs- All cells have specific antigens on their surface - Monoclonal antibodies can be made to bind to any target cell- Attach the drug to the specific antibodies which will then form an antigen-antibody complex with the target cells antigens- Drug and antibody will only bind to target cells
36
How are monoclonal antibodies used in medical diagnosis?
- Monoclonal antibodies fixed to a plate- Sample e.g. blood plasma added- if sample contains the complimentary antigen and antibody-antigen complex will form and the antigens will bind to the antibody- Rinsed to remove unbound antigens- The same monoclonal antibody is added with an enzyme/colour marker - New antibody will also be able to bind to the antigen if it was present in the sample- Sample rinsed to remove unbound antibodies and enzymes- Observing will give a positive/negative. Either a colour change or if an enzyme was used a substrate will need to be added to identify whether or not it was catalysed
37
What is a vaccine?
It contains antigens from a dead/weakened pathogen which stimulate the immune response to produce antibodies/plasma cells/memory cells
38
What happens if you are infected post vaccination?
It is a secondary response because you already have memory B-cells for the complimentary antibody therefore you don't feel symptoms
39
Why are vaccines usually injected?
If taken orally they may be to big to absorb or they can be broken down by the stomach acid
40
What is antigenic variability?
The ability of a pathogen to change the antigens on its surface so the antibodies produced by your memory B-cells are no longer complimentary are upon reinfection you have to go through the primary immune response
41
How can the same pathogen have different antigens?
- Antigenic variability- Pathogen may have multiple strains
42
What is active immunity?
When you produce your own antibodies
43
What is passive immunity?
When you are given antibodies by another organism
44
Give an example of natural active immunity
You get infected by a pathogen and undergo a primary immune response
45
Give an example of artificial active immunity
You receive a vaccine and undergo a primary immune response
46
Give an example of natural passive immunity?
You are given antibodies by your mother either in breast milk or the placenta
47
Give an example of artificial passive immunity?
You receive someone else antibodies through a blood transfusion
48
Compare active and passive immunity
Active:- Slow- Long term- Make memory cells- Exposed to antigen Passive:- Fast - Short term (foreign antibodies are broken down by the body) - No memory cells- Not exposed to antigen
49
What is ELISA?
Enzyme LinkedImmunoSorbent Assay
50
What is an ELISA used for?
Testing whether patients have a specific antibody or antigen
51
How do ELISAs give results?
They use antibodies bound to enzymes which when the complimentary substate is added a colour change can be observed
52
What is a Direct ELISA?
- Test for antigens - Immobilised antibodies are fixed to a well
53
What is an Indirect ELISA?
- Test for antibodies- Immobilised antigens are fixed to a well
54
How is a direct ELISA carried out?
1 - Immobilised antibodies are fixed to a well2- Sample added (blood plasma)3- If blood plasma contains complementary antigens then an antigen-antibody complex will form4- Rinse to remove unbound antigens5- Same antibody with an enzyme is added6- Rinse to remove unbound antibodies7- Add substrate 8- Observe
55
How is an indirect ELISA carried out?
1 - Immobilised antigens are fixed to a well2- Sample added (blood plasma)3- If blood plasma contains complementary antibodies then an antigen-antibody complex will form4- Rinse to remove unbound antibodies5- Different antibody with an enzyme is added which will only bind if the first antibody is present 6- Rinse to remove unbound antibodies and enzymes 7- Add substrate 8- Observe
56
What is HIV?
Human Immunodeficiency Virus
57
What does HIV do?
Infects helper T-cells weakening immune system which leads to the development of AIDS
58
What is AIDS?
Acquired Immune Deficiency Syndrome
59
How can people die from HIV?
HIV doesn't directly kill you, your immune system becomes so weak it cannot fight any pathogens and you usually die from pneumonia/TB
60
How does HIV replicate?
- Virus attachment protein binds to a receptor on the TH-cell- Reverse transcriptase makes double stranded DNA from the viruses RNA- DNA enters the nucleus through the nuclear pore- TH-cell makes more copies of the viruses RNA and reverse transcriptase - Capsid reforms- Virus (RNA and reverse transcriptase) leaves host cell and takes an envelope from hosts membrane
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