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Aqa A Level Bio > Immunity > Flashcards

Immunity Flashcards

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1
Q

How are cells identified by the immune system

A

Each type of cell has specific molecules on its surface that identify it

3d tertiary structure enables lots of unique and identifiable shapes to be made

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2
Q

What types of cells and molecules can the immune system identify ?
Non self cells

A

Detected a response will be triggered to destroy the cell

  1. Pathogens
  2. Cells from other organisms of the same species
    3.abnormal body cells
    4.toxins
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3
Q

Antigens

A

Protein on the surface of a cell that produces an immune response

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4
Q

Why does immune response occur and what are the two types?

A

If pathogens get past the chemical and physical barriers and enter the blood then the white blood cells are the second line of defence

Phagocytes - non specific
Lymphocytes - specific

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5
Q

Describe phagocytosis of pathogens(non-specific immune response )

A
  1. Phagocyte moves towards pathogen via chemotaxis.
  2. Phagocyte engulfs pathogen via endocytose to form a phagosome
    3.phagosome fuses with lysosome
    4.lyzozomes digest pathogen
  3. Phagocyte absorbs the products from pathogen via hydrolysis
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6
Q

Antigen presenting cells APC

A

Macrophage displays antigen from the pathogen on its surface
- happens after hydrolysis in phagocytosis
- enhances recognition by Th cells which cannot directly interface with pathogens

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7
Q

Cell mediated response - specific

A

Made in bone marrow
Matured in thymus

1.complementary Th lymphocytes bind to foreign antigen on apc
2. Releases cytokines that stimulate
-Activate Th cells
Which divide by mitosis - replicate making a large number of clones
3.Cloned th cells diffrentiate into different cells
-Activate b cells - humoural response
-Memory cells - copy specific antigen
-Clonal expansion Cytotoxic T cells -
Secrete enzyme perfoin to destroy infected cells

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8
Q

Cytotoxic T cells

A

Only kill own infected cells
Release chemical called perform
Which puts a hole in membrane sacrifices the cell.

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9
Q

Humoural response - b cells

A

Made in bone marrow matured in bone marrow
Lymphocytes are white blood cells involved in specific immune responses

  1. Complementary Th lymphocytes bind to foreign antigen
    Presented with a foreign antigen
  2. Release cytokines that stimulate complementary b lymphocytes
  3. Activates b cells
  4. Clonal expansion
    Differentiate into 2
    Plasma b cells - produce antibodies - destroy pathogen - primary immune response

B memory cells -long term immunity
Secondary immune response - produce antibodies faster

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10
Q

Primary and secondary response

A

Primary - exposed to new pathogen new antigen takes longer for antibodies to produce as you need to go through b cells to find
Few days

Secondary - memory b cellls antibodies created faster

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11
Q

Antibodies

A

Proteins secreted by plasma cells
Quaternary structure proteins
4 polypeptide chains
2 light chains held together by disulphide bridges
2 longer heavy chains
Rest of molecule known as constant region
- binding site in variable region of light chain have specific tertiary structure to an antigen

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12
Q

How do antibodies lead to destruction of a pathogen

A

Antibodies help destroy pathogens by agglutination

  1. Formation of antigen- antibody complex
  2. Results in aggulatoon which enhances phagocytosis
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13
Q

Definition of vaccine
Explain the principles of vaccination

A

Injection of antigen from dead microorganism which stimulates formation of memory cells

  1. Vaccine contained dead pathogen
    2.Triggers primary immune response
  2. Memory cells are produced and remain in bloodstream so secondary response is rapid and produces higher concentration of antibodies
    4.pathogen is destroys before it can cause symptoms
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14
Q

Types of vaccines
Active and passive

A

-both involve antibodies
-can be both natural or artificial

Active - weekend form of the pathogen injected into the body to cause
Slower
Acquired immunity

Passive - introduction of antibodies from the outisde source.
Rapid
Natural immunity

-passive natural immunity: antibodies in breast milk
-passive artificial - needle stick infection
-active natural - humoral response to infection
-active artificial- vaccination

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15
Q

Contrast passive and active immunity

A

Active - direct contact needed with antigen
- memory cells produced Long term protection
- time lag
Lymphocytes produce antibodies

Passive - no direct contact needed with antigen
-uses antibodies from external sources
- immediate response short term protection
- no memory cells produced

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16
Q

Natural and acquired immunity

A

Natural - passed from the mother to child
Through placenta or breast feeding

Acquired
Injected by a pathogen caused an immune response

17
Q

Explain how vaccines provide protection to individuals against disease

A
  • specific b lymphocytes with the complementary receptor binds to antigen
    -specific T helper cell binds to apc stimaulated b cell
  • b lymphocytes divide by mitosis to form clones
    -some differentiate into b plasma cells which release antibodies
  • some differentiate into memory cells
  • on secondary exposure to antigen b memory cells rapidly divide by mitosis to produce b plasma cells
  • these release antibodies faster and a higher concentration
18
Q

Antigen variability

A

Mutations in the DNA of the pathogen can lead to the antigen changing shape

Antibodies produce are not complementary

Vaccines are hard to make

19
Q

Herd immunity

A

-Vaccinating large proportion of population
-reduces available carries of the pathogen

*Provides protection against those who are not vaccinated for reason .
-Pregnancy
-Too young
- weak immune system

20
Q

Virus

A

A cellular
Non loving
Only active once inside the cell
Incase host cell and replicates

21
Q

Hiv structure

A

No cytoplasm - can’t carry out any metabolic reaction on its own

-2x rna and viral enzymes surrounded by capsid
- surrounded by viral envelope derived from host cell membrane
Attachment protein - attach to host cell
Can attach to receptor protien

May contain enzymes only work inside the host cell

22
Q

Hiv

A

Single stranded RNA- no dna
Reverse transcriptase- enzyme
Retrovirus
Converts RNA BACK to DNA

23
Q

Method of infection for HIV

A
  1. HIV attachment proteins attach to receptors on helper T cell.
  2. The virus enters the host cell. Hiv uses reverse transcriptase converting RNA TO DNA
  3. The viral DNA is joined to host DNA . Dna is used to make HIV RNA
  4. Ribosomes make hiv proteins
    5.. new virus particles assemble
    Bud off the host membrane
24
Q

Leads to aids

A
  1. Attachment proteins bind to complementary CD4 receptor on Th cells
  2. HIV particles replicate inside Th cells killing / damaging them
    3.AIDS develops when there are too few Th cells for the immune system to function. Can’t activate b / T cells
  3. Pathogens reproduce and release toxins and damage cells
    5.
25
Q

Monoclonal antibodies

A

-Antibodies produces a single clone of b cells
-same tertiary structure

26
Q

Cancer therapies - using monoclonal

A
  1. Cancer cells produce a tumour marker
  2. Antibodies are made complementary to the maker
    3.we attach a drug to the antibody
  3. When antibody binds to drug kills the cancerous cell
27
Q

Reduce injection - antibody therapy

A

Use genetic engineering to create homanized mABS
These consist of mainly humanly polypeptide chains
With only amino acids at the antigen binding site derived from mice

28
Q

Pregnancy testing

A

1.Find the pre scene of the hormone hcG in the urine
2.antibodies for hcG are bound to a coloured bead (blue )
3. When urine is applied hcG bind to the antibody on the head
Forming antibody complex
4. Urine moves up the stick to the test strip carrying any beads with it
5. Test strip contains antibodies to hcG that are stuck in place
6. If hcG present strip turns blue
Immobiliser Antibody bind to it
No hcG go straight through won’t bind won’t turn blue

29
Q

Ethical issues of monoclonal antibodies

A

-Requires mice to produce antibodies and tumour cells
Use of animals
-use of drug - side effects

30
Q

2 difference between specific and non specific immune response

A

Non specific (phagocytosis)- same for all pathogen
Immediate response

Specific -(lymphocytes) complementary to pathogen
-time lag

31
Q

Why are antibiotics ineffective against viruses ?

A
  • antibiotics work by damaging then cell walls to cause osmotic lysis
  • viruses have no cell wall
  • viruses replicate inside host cells
  • difficult to destroy them without damaging normal body cells
32
Q

Ethical issues with the use of vaccines

A

Clinical trials on humans - potential harm / side effects
Vaccines - may continue pass on the pathogen

33
Q

Points to consider when evaluating methodology relating to the use of vaccines and monoclonal antibodies

A
  1. Was sample side large enough
  2. Were participants diverse in age , sex , health status
    3.placebo / control groups used for comparison
  3. Was duration of the study long enough to show long term effects
  4. Was the trail double - blind to reduce bias
34
Q

Points to consider when evaluating evidence and data relating to the use of vaccines and monoclonal antibodies

A
  • was a statistical
35
Q

Points to consider when evaluating evidence and data relating to the use of vaccines and monoclonal antibodies

A
  • was a statistical test used to see if there was a significant diffence between start and final results.
    -was the standard deviation of final results large - showing people did not benefit
    -did standard deviations of start and final results overlap showing there may not be significant difference
    -what dosage was optimum? Does increasing dosage increase effectiveness enough to justify extra cost
  • was the cost of production and distribution low enough
36
Q

Explain the principle of a direct Elisa test

A
  • detects pressen of a specific antigen
    1) monoclonal antibodies bind to bottom of the test plate
    2) antigen molecules in sample bind to antibody . Rinse excess
    3) mobile antibody with reporter enzyme attached bind to antigen that are fixed on the monoclonal antibody - rinse excess
    4) add substrate to reporter - colour change positive result
37
Q

Explain the principle of a indirect elisa test

A
  • detects prescience of an antibody against of a specific antigen
    1) antigens bind to bottom left of the test plate
    2) antibodies in the sample bind to antigen . Wash excess
    3)secondary antibody with reporter enzymes attached bind to primary antibodies from the sample
    4) Add substrate for reporter enzyme -> colour change

Aqa A Level Bio (10 decks)

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