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AS AQA BIOLOGY > Immunity > Flashcards

Immunity Flashcards

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1
Q

Define immunity

A

the means by which the body protects itself from infection

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2
Q

Outline a non specific defence mechanism

A

Immediate response
Same for all pathogens

Physical barriers and phagocytosis

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3
Q

Outline a specific defence mechanism

A

Slower response
Specific to each pathogen

Cell mediated response and humoral responce

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4
Q

Name 3 physical barriers

A 
Skin
Mucus
Ear wax
Hair
Tears
Stomach Acid
Scabbing
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5
Q

Why does the body’s immune system take a number of days to control an infection?

A

Lymphocytes must build up their numbers/replicate

And this takes a long time

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6
Q

Why is it incorrect to say the body takes several days to respond to infection?

A

The body responds immediately by recognising foreign antigens
And carrying out phagocytosis

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7
Q

Briefly outline phagocytosis

A
  1. Phagocyte identifies pathogen
  2. Receptors bind to pathogen
  3. Pathogen trapped in phagosome
  4. Lysosomes fuse with phagosome
  5. Pathogen is hydrolysed
  6. Antigen is displayed of phagosome cell surface
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8
Q

How are pathogens destroyed in phagocytosis

A

Lysosomes containing enzymes
Lysozymes
Hydrolyse the pathogen

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9
Q

Why might phagocytes be abundant in tears?

A

Protective covering of the eye and tear ducts are pathogen entry points
Tears hydrolyse pathogens that try to enter through the eye
Before infection and harm can occur

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10
Q

Define antigen

A

A molecule from the cell surface membrane
That triggers an immune response
By lymphocytes

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11
Q

What are the two types of lymphocyte?

A

B lymphocytes

T lympohcytes

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12
Q

Briefly outline cell-mediated immunity

A
  1. Receptors on Th cells fit onto antigens displayed on phagocytes cell surface
  2. Th cell activates
  3. Th cell rapidly divides by mitosis to form clones
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13
Q

What can a clones T helper cell do?

A

Develop into a memory cell
Stimulate phagocytes to perform phagocytosis
Stimulate B cells to divide
Activate Tc Cells

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14
Q

How does a cytotoxic T cell kill infected cells?

A

Produces a protein; Perforin
That makes holes in the cell surface membrane
Allowing free movement of substances
Destroying the cell

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15
Q

Which type of pathogen are Tc cells most effective against?

A

Virsuses

They use living cells to replicate

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16
Q

Name 2 similarities between T cells and B cells

A 
Both white blood cells
Both lymphocytes
Both have a role in immunity
Both produced from stem cells
Both produce memory cells
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17
Q

Name 2 differences between T cells and B cells

A

Mature in: T cells = thyumus gland, B cell = bone marrow
T Cell = cell-mediated immunity, B cell = homural immunity
T Cells cant produce antibodies, B cells can
T Cells only detect presented antigens, B cells detect any antigens

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18
Q

Briefly outline humoral immunity

A
  1. B cells take up and process antigens
  2. Th cells activate the B cell
  3. The B cell rapidly divides by mitosis to form clones
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19
Q

What can cloned B cells do?

A

Become plasma cells

Become memory cells

20
Q

What does a plasma cell do?

A

Produces antibodies
Only survive a few days
Produce 2000 antibodies a second

21
Q

What does a memory cell do?

A

Survive for up to decades
Rapidly divide into new T cells and B cells when they encounter a specific antigen
Providing long term immunity

22
Q

Why is a secondary immune response more rapid than a primary immune response?

A

Antigens have not been ingested, processed or presented in a primary response
The immune response takes time as these steps must occur consecutively

In a secondary response memory cells are present and only require cloning and development into plasma cells
Fewer processes mean a quicker response

23
Q

Outline 2 differences between Cell-mediated immunity and humoral immunity

A

Cell-mediated = T cells, Humoral = B cells
Cell mediated = no antibodies, Humoral = antibodies
Cell mediated = effective through cells, humoral = efffective through body fluid

24
Q

Outline 2 similarities between Cell-mediated immunity and humoral immunity

A

Both immune responses
Both specific immune responses
Both produce memory cells
Both require antigens

25
Q

Define antibody

A

A protein produced by lymphocytes in response to the presence of an appropriate antigen

26
Q

Outline the structure of an antibody

A

Four polypeptide chains; 2 heavy chains, 2 light chains
Binding site that is complimentary to specific antigen
Variable region that results in different binding site shapes
Constant region that binds to receptors on cells (eg b cells)

27
Q

How does an antibody lead to the destruction of an antigen?

A

Agglutination; clumps bacterial cells together for easier location by phagocytes
Serve as markers to stimulate phagocytosis

28
Q

Define monoclonal antibody

A

An antibody produced by a single clone of cells

29
Q

How can antibodies be used in medicine?

A

Targeting cancer cells
Diagnosis of diseases
Pregnancy testing

30
Q

Name 2 ethical pros of using antibodies in medicine

A

Treat life threatening diseases such as cancer
Diagnose life threatening diseases
Rapid results
More effective than other methods of treatment

31
Q

Name 2 ethical cons of using antibodies in medicine

A

Involves use of mice by giving mice cancer
Has resulted in some deaths; multiple sclerosis
Trial tests in March 2006 resulted in all volunteers suffering multiple organ failure

32
Q

Define passive immunity

A

resistance to disease that is acquired from the introduction of antibodies from another individual rather than your own immune system

33
Q

Define active immunity

A

resistance to disease resulting from the activities of an individuals own immune system whereby an antigen induces plasma cells to produce antibodies

34
Q

What is the difference between natural active immunity and artificial active immunity

A

Natural results from an individual becoming infected and producing its own antibodies

Artificial comes from vaccination and results in the production of antibodies due to exposure to the antigen, but no infection

35
Q

What signs must a vaccination show to be successful?

A 
Economically beneficial
Few side effects
Easily produced, transported and stored
Means of administration available
Majority of vulnerable population must be vaccinated
36
Q

Define her immunity

A

Majority of the population is vaccinated
So pathogen is difficult to spread
Protecting susceptible individuals

37
Q

Why might a vaccination not eliminate a disease?

A 
Vaccination fails to induce immunity
Infection immediately after vaccination
Frequent mutation of the pathogen
Too many varieties of the pathogen
Pathogens hiding in body cells
Objections of vaccination (eg religion)
38
Q

Define antigenic variablity

A

A change in a pathogens antigens resulting in the immune system no long producing antibodies to destroy the pathogen

39
Q

Name 3 ethical questions that should be taken into account with vaccination

A

How acceptable is vaccine production?
How can side-effects be balanced against the risk of infection?
Who should vaccines be tested on?
Should vaccines be compulsory?
Should vaccination continue when the disease is almost eradicated?
Should vaccines with unknown side effects be issued in emergency situations?

40
Q

What does HIV stand for?

A

Human immunodeficiency virus

41
Q

What does AIDS stand for?

A

Acquired Immune deficiency syndrome

42
Q

Outline the structure of HIV

A 
Lipid envelope on outside 
With attachment proteins embedded
Capsid inside protein layer
Two strands of RNA inside capsid
Reverse transcriptase inside capsid
43
Q

How does HIV replicate?

A
  1. HIV enters blood stream and circulates body
  2. HIV binds to helper t cells
  3. Capsid fuses with cell surface membrane and contents of HIV enter cell
  4. HIV reverse transcriptase converts RNA into DNA
  5. New DNA inserts into cell’s DNA
  6. Messenger RNA creates new viral proteins and RNA
  7. HIV is pieced together and burst from the cell
44
Q

How does HIV cause AIDS?

A

HIV attacks T helper cells
Reducing the number of T helper cells
So B cells cannot be stimulated
Resulting in a lack of adequate humoral response

45
Q

What does ELISA stand for?

A

Enzyme linked immunosorbant assay

46
Q

Outline the ELISA test

A
  1. Antigens attach to a surface
  2. Wash to remove unattached antigens
  3. Add antibody specific to antigen so they bind
  4. Wash to remove excess antibody
  5. Add second antibody to bind with first antibody with attached enzyme
  6. Add colourless substrate of enzyme
  7. Enzyme hydrolyses substance if present, giving a coloured positive result

AS AQA BIOLOGY (8 decks)

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