2.4 Immunity

Question 1

name 4 things the body needs to defend itself from

Answer 1

• pathogens
• Non-self material such as cells from other organisms of same species
• toxins such as those produced by a certain pathogen
• abnormal body cells like cancerous cells

Question 2

what does a phagocyte do

Answer 2

ingest and destroy the pathogen by phagocytosis

Question 3

what does a lymphocyte do

Answer 3

evolves an immune response

Question 4

what are the 6 steps of phagocytosis

Answer 4

1. phagocyte recognises the foreign antigens
2. pathogen is engulfed
3. this is enclosed in a vesicle
4. the vesicle fuses with the lysosomes
5. the lysosome releases enzymes
6. pathogen is digested

Question 5

define antigen

Answer 5

a protein on the cell surface membrane of an organism that is recognised as foreign by the immune system

Question 6

what are the 2 types of lymphocytes

Answer 6

B lymphocytes
T lymphocytes

Question 7

define B lymphocytes

Answer 7

mature in the bone marrow
they are associated with humeral immunity

Question 8

define T lymphocyte

Answer 8

mature in thymus gland
they are associated with cell mediated immunity

Question 9

what are cells that display foreign antigens on their own cell-surface called

Answer 9

Antigen presenting cells (APCs)

Question 10

5 steps of T lymphocytes response:

Answer 10

1. pathogens invade body cells or are taken in by phagocytosis
2. the phagocytes places antigens from the pathogen on its cell-surface membrane
3. receptors on specific T helper cell are complementary to this specific antigen
4. this attachment activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells
5. the cloned T cells; develop into memory cells allowing for future fast responses, stimulates phagocytosis, stimulates B cells to divide and secrete antibodies and activates cytotoxic T cells

Question 11

Define cytotoxic T cell

Answer 11

they kill abnormal cells by making holes in the cell surface membrane meaning it becomes freely permeable to all substances and it dies as a result

Question 12

what are the 2 types of B cells

Answer 12

plasma cells and memory cells

Question 13

what are plasma cells

Answer 13

secrete antibodies but only survive for a few days, these antibodies lead to the destruction of the antigen which is an immediate defence against infection
this is primary immune response

Question 14

what are memory cells

Answer 14

these can live for decades, they don’t directly produce antibodies but they circulate in the blood. if they encounter the same antigen they will rapidly divide and develop into plasma and more memory cells.
this is secondary immune response

Question 15

step of B cells

Answer 15

1. the surface antigens of invading pathogens are take up by a B cell
2. the B cell processes the antigens and displays them on its own cell surface
3. Helper T cells attach to the processes antigens and activates the B cells
4. the B cell now divides by mitosis to give a clone of plasma cells
5. the cloned plasma cells produce a specific antibody that exactly fits the antigen on the pathogens surface
6. the antibody destroys the antigens on the invading pathogen
7. some B cells develop into memory cells for secondary immune response

Question 16

what are antibodies made from

Answer 16

4 polypeptide chains where one pair is light (shorter) and the other is heavy (longer)

Question 17

how do the antibodies lead to the destruction of antigens

Answer 17

• they cause agglutination of the cells where clubs of them are formed making it easier for the phagocytes to ingest them
• they then serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached

Question 18

how can monoclonal antibodies target specific cells

Answer 18

the antibodies are specific to the cancerous cells antigens, these antibodies attach to the caner cells only, they block the chemical signals that stimulate their uncontrolled growth

Question 19

how are monoclonal antibodies used in pregnancy testing

Answer 19

pregnant women produce more hCG in their urine, these monoclonal antibodies are present on the test strip and if hCG is present then it will end to these antibodies and move along the strip until trapped by a different antibody creating a coloured line

Question 20

ethical problems of MAbs

Answer 20

to produce them mice have to be given cancer
unknown risks

Question 21

what is passive immunity

Answer 21

the introduction of antibodies into individuals from an outside source, so no memory cells produced so not long term

Question 22

what is natural passive immunity

Answer 22

a baby getting antibodies through the placenta and in breast milk

Question 23

what is artificial passive immunity

Answer 23

injected with antibodies such as anti-venom in snake bites

Question 24

what is active immunity

Answer 24

stimulating the production of antibodies by the individuals own immune system, longer lasting and memory cells are produced

Question 25

what is natural active immunity

Answer 25

individual becoming immune after getting infected with a disease as now have antibodies

Question 26

what is artificial active immunity

Answer 26

vaccination injecting a harmless dose of the antigen

Question 27

what is herd immunity

Answer 27

when a sufficiently large proportion of the population has been vaccinated the pathogen will have a hard time spreading between the population

Question 28

ways that vaccination may not eliminate disease:

Answer 28

- vaccination fails to introduce immunity to certain individuals - individuals may develop the disease immediately after the vaccination so immunity level not high enough - pathogen may mutate changing its antigens - some people may object the vaccine through medical or ethical reasons

Question 29

ethical issues with vaccines

Answer 29

- production of vaccines often involve animals - vaccines have side effects that can cause harm

Question 30

8 steps of HIV replication

Answer 30

1. HIV enters the bloodstream and circulates around the body 2. Glycoprotein molecules on the virus' surface bind to CD4 receptors on T helper cells 3. this allows the virus envelope to fuse with the T helper cell membrane 4. the capsid is released into the cell where is releases RNA and reverse transcriptase 5. Reverse transcriptase is used to make DNA from the HIV RNA template 6. The DNA is inserted into the cells DNA which gets replicated when the cells replicate 7. DNA is used to make HIV RNA and proteins at host ribosomes 8. Virus particles are assembles which bud off from the cell membrane and go on to infect other cells

Question 31

how does HIV cause AIDS

Answer 31

HIV attacks T helper cells, without a sufficient amount to T helper cells the immune system cannot stimulate B cells to produce antibodies. As a result the immune system is weak

Question 32

what is ELISA test for

Answer 32

To detect HIV

Question 33

7 step of the ELISA test

Answer 33

1. apply the sample to a surface ti which all the antigens are complementary 2. Wash the surface several times to remove any unattached antigens 3. add the antibody that is specific to the antigen we are trying to detect and leave the two to bind together 4. wash the surface to remove excess antibody 5. add a second antibody that binds with the first antibody which has an enzyme attached to it 6. add the colourless substrate of the enzyme. the enzyme acts in the substrate to change into a coloured product 7. the amount of the antigen present is relative tot he intensity of the colour test

Question 34

why are antibiotics ineffective against a viral disease

Answer 34

one way antibiotics work is by preventing bacteria from making normal cell walls. so water enters the cell via osmosis and as there is no murrain o protect the cell then the cell bursts. However, viruses rely on host cell to carry out their metabolic activities therefore antibiotics are ineffective as there are no metabolic structures for them to disrupt