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Biology A-level > Immunity > Flashcards

Immunity Flashcards

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1
Q

What does HIV stand for

A

Human immunodeficiency virus

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2
Q

Why is HIV known as a retrovirus

A

it possess RNA and reverse transcriptase which can make DNA from RNA- a reaction that is the reverse of that carried out by transcriptase

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2
Q

What is the difference between HIV and AIDS

A

-HIV is a virus while AIDS describes the condition caused by infection with HIV

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3
Q

Describe how HIV is replicated

A

-attachment proteins attach to receptor on t-helper cell
-RNA enters cell
-reverse transcriptase converts RNA to DNA
-HIV DNA inserts into host DNA
-uses human enzymes (transcription and translation) to make copies of RNA and proteins
-Viral protein assembled and released

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4
Q

Symptoms of HIV

A

-low number of T-helper cells
-less antibodies which causes infection more

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5
Q

What does HIV cause

A

AIDS

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6
Q

How is HIV diagnosed

A

measure T helper cell count in blood

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7
Q

Pathogen

A

Microorganism that causes disease (bacteria, virus and fungi)

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8
Q

Immunity

A

When the bodies defence mechanisms overwhelm a pathogen and destroy it.

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9
Q

What are the 2 types of defence mechanisms

A

-General, immediate defences (skin, phagocytosis
-Specific responses (T-cells, B-cells)

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10
Q

Antigens

A

part of an organism that is identified as non-self that triggers an immune response

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11
Q

What are 4 materials that the body can recognise as non-self

A

-Pathogens
-Cells from other organisms
-Toxins
-Abnormal body cells (cancer)

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12
Q

Phagocytosis

A

-Pathogen secretes chemicals and phagocyte detects them
-Pathogen binds to a receptor
-membrane binds to the pathogen in a vesicle as a phagosome
-Phagosome binds to the lysosome turning into a phagolysosome
-Lysozymes hydrolyse pathogen
-waste material leaves via exocytosis

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13
Q

Describe how phagocytosis of a virus leads to presentation of its antigens

A

-phagosome fuses with lysosome
-Destroyed by lysozymes
-antigen is displayed on the cell membrane

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14
Q

Describe how presentation of a virus antigen leads to the secretion of an antibody against the antigen

A
  • Helper t-cells bind to the antigen
    -stimulates a specific B cell
  • B cell clones
    -Forms plasma cells that release antibodies
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15
Q

Describe how HIV is replicated once inside helper T cells

A

-RNA converted into DNA using reverse transcriptase
-DNA inserted into nucleus
-DNA transcribed to HIV mRNA
-HIV mRNA translated into viral protein

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16
Q

Describe how a phagocyte destroys a pathogen present in the blood

A

-Engulfs
-forming vesicle and fusing with lysosome
-Enzymes hydrolyse

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17
Q

Give two cells other than a pathogen that can stimulate an immune response

A

-abnormal body cells (cancer)
-Cells from other organisms

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18
Q

What is the role of the disulfide bridge in forming the quaternary structure of an antibody?

A

Joins two different polypeptides

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19
Q

Explain how HIV affects the production of antibodies when AIDS develops in a person

A
  • less antibodies produced
  • because HIV destroys T helper cells
    -Fewer B cells activated
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20
Q

What response do T cells produce

A

Cell mediated

21
Q

What response do B cells produce

A

Humoral

22
Q

What is the cell mediated response

A

-pathogen invade body cells
-phagocyte places antigen on cell surface
-receptor on T helper fits antigen
-activates rapid mitosis of T cells
-Stimulates: memory cells to develop, phagocytes, B cells and cytotoxic cells

23
Q

What is a cytotoxic T cell

A

Kill abnormal cells and body cells by producing perforin that makes hole in the cell surface membrane
-Useful against viral infections

24
Q

What is the humoral response

A
  • B cells produces from the cell mediated response
    -Clonal selection
    -B cells differentiate into Plasma cells and memory cells
    -Plasma cells secrete antibodies
25
Q

Describe how B-lymphocytes respond when they are stimulated by antigens.

A

divide by mitosis / form clones;
produce plasma cells;
(plasma cells) make antibodies;
(plasma cells) produce memory cells;

26
Q

Agglutination

A

Group of antibodies clump together the pathogens making them easier to locate and stimulate phagocytosis

27
Q

Monoclonal antibodies

A

Antibodies produced from a single clone of B cells

28
Q

Active immunity

A

Produced by stimulating the production of antibodies by the individuals own immune system through exposure to antigen or pathogen

29
Q

What are the 2 types of active immunity

A

Natural and artificial

30
Q

Natural active immunity

A

results from an individual becoming infected under normal circumstances and the body producing its own antibodies and memory cells

31
Q

artificial active immunity

A

following the introduction of a weakened version of the pathogen or antigen via vaccine

32
Q

Passive immunity

A

Produced by the introduction of antibodies from an outside source, no memory cells are formed so immunity isn’t lasting

33
Q

example of passive immunity

A

antibodies passed on to a foetus through the placenta
-through breast milk to a baby

34
Q

vaccination

A

a small amount of weakened or dead antibody or pathogen is introduced in the mouth or by injection

35
Q

What does the introduction of a vaccination do

A

-exposure to antigen stimulates B cells to go through clonal expansion and differentiation
-B cells undergo mitosis to make large numbers of cells which differentiate into plasma cells and memory cells
-B memory cells can rapidly divide into plasma cells upon reinfection with the same pathogen to make large numbers of antibodies

36
Q

Describe the features of an effective vaccination programme

A
  • suitable vaccine, economically available to most of the vulnerable population
  • few side effects to prevent people from refusing the vaccine
  • means to produce, store and transport the vaccine
  • means of effectively administering vaccine
  • possible to vaccinate majority of vulnerable population - herd immunity
37
Q

Herd immunity

A

Once a large enough percentage of a population is vaccinated this will protect the unvaccinated individuals as it’s hard for the pathogen to spread

38
Q

why is herd immunity important

A

because it’s never possible to vaccinate everyone in a large population such as babies and young children because their immune systems aren’t fully functional

39
Q

Explain why vaccination rarely eliminates a disease

A
  • vaccination does not cause immunity in some individuals
  • individuals develop disease immediately after vaccination before immunity is reached
  • pathogen mutates so vaccines no longer cause effective immunity - antigenic variability
  • many varieties of a pathogen so impossible to develop vaccine to all
  • some people may be against vaccination for religious, ethical or medical reasons
40
Q

Antigenic variability

A

If a pathogen has a high mutation rate and the genes of the pathogen change leading to the antigen on the cell surface being different the antibodies produced will no longer be effective

41
Q

Discuss the ethical issues associated with vaccination programmes

A
  • use of animals in development of vaccines
  • side effects that may cause long term harm
  • whom should vaccines be tested on?
  • should vaccination be compulsory
  • should vaccination continue when disease incidence is low
42
Q

How can lymphocytes distinguish between self and non self cells

A

The proteins that make up the cells are different as they have variety and a highly specific tertiary structure

43
Q

What is the structure of an antibody

A

-4 polypeptide chains
-1 pair light/ 1 pair heavy
every antibody has a specific binding site to form antigen antibody complex (variable region)

44
Q

What ways can monoclonal antibodies be used in medical treatment

A

-monoclonal antibody therapy for cancer by attaching to receptors to stop the rapid uncontrolled growth
-Medical diagnosis- by looking at the levels of antigens produced in things such as cancer
-pregnancy tests- Measured the hcg production

45
Q

Direct monoclonal antibody therapy

A

-cancer can be treated by monoclonal antibodies which are designed with a binding site that’s complimentary to the antigen
-while the antibodies are bound to the cancer antigen, this prevents chemical binding to the cancer cells which enable uncontrolled cell division
-which prevents growth

46
Q

Indirect monoclonal antibody therapy

A

-antibodies have drugs attached to them that are complementary to the cancer cell
-drugs are therefore delivered directly to the cancer cells and kill them which reduces side effects from chemotherapy and radiotherapy

47
Q

The Elisa test- pregnancy test

A

-first mobile antibody, complimentary to the antigen being tested for has a coloured dye attached
-a second antibody complimentary in shape to the antigen is immobilised in the test
-A third antibody is immobilised an is complimentary in shape to the first antibody

48
Q

The elisa test

A

-Add the test sample from a patient to the base of the beaker.
-Wash to remove any unbound test sample.
-Add an antibody complementary in shape to the antigen you are testing the presence of in the test sample.
-Wash to remove any unbound antibody.
-Add a second antibody the is complementary in shape to the first antibody, and binds to the first. The second antibody has an enzyme attached to it.
-The substrate for the enzyme, which is colourless, is added. This substrate produces coloured products in the presence of the enzyme.

49
Q

What does the presence of colour in the elisa test indicate

A

the presence of the antigen in the test sample and the intensity of the colour indicates the quantity

50
Q

What are ethical issues linked with the use of monoclonal antibodies

A

-The production of monoclonal antibodies involves the induction of tumour cells into mice
-There have been deaths associated wit the use of monoclonal antibodies when been used for treatment
-When testing for new drugs healthy volunteers have suffered multiple organ failures probably due to the production of T cells overproducing chemicals

51
Q

Why are antibiotics ineffective against viruses

A

There are no metabolic processes or cell structures to disrupt. Viruses have a protein coat rather than a cell wall and so don’t have sites for antibiotics to work. when viruses are within an organisms own cells antibiotics cannot reach them.

Biology A-level (31 decks)

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