immune system 3.2.4

Question 1

what is an antigen

Answer 1

any part of an organism or substance that is recognised as non self by the immune system

protein that stimulates an immune response

Question 2

4 examples that act as antigens

Answer 2

pathogens
non self material
cancerous cell antigens
toxins

Question 3

phagocytosis

Answer 3

1 phagocyte attracted to chemicals produced by pathogen
2 recognises pathogen antigens and binds
3 engulfs pathogen forming phagosome
4 lysosomes fuse with phagosome
5 lysozymes hydrolyse pathogen
6 phagocyte presents pathogens antigens to activate other immune cells

Question 4

cellular response (T cells)

Answer 4

1 pathogen attacks body cell
2 infected phagocyte cell presents antigens
3 helper T cell with complementary shaped receptors binds to the antigens
4 helper T cell activated to divide by mitosis producing clones

Question 5

what can T cell clones differentiate to do

Answer 5

memory cells
stimulate phagocytosis
stimulate B cells
activate cytotoxic T cells

Question 6

what do cytotoxic T cells do

Answer 6

kill infected cells by forming pores in the membrane
using a protein called perforin

Question 7

humoral response (b cells)

Answer 7

1 b cell binds to complementary antigen
2 b cell ingests processes and presents antigens
3 helper t cell with complementary receptors attaches to presented antigens on b cell
4 b cell is stimulated to divide via mitosis, forming clones
5 clones differentiate into memory cells and plasma cells
6 plasma cells release/produce antibodies (against specific pathogen)

Question 8

what is another word for b cell ingesting

Answer 8

endocytosis

Question 9

what is clonal selection

Answer 9

when specific antigens select specific b cells that are complementary and stimulate them to form clones

Question 10

define antibody

Answer 10

protein produced by the immune system in response to a specific antigen

Question 11

list parts/structure of antibody

Answer 11

light chain
heavy chain
variable region
constant region
disulphide bridge
antigen binding site

Question 12

what is agglutination

Answer 12

clumping together of bacterial cells so phagocytes can easily engulf them in a group

Question 13

define active immunity

Answer 13

results from immune system producing memory cells following exposure to an antigen

Question 14

define passive immunity

Answer 14

results from being given antibodies from a different organism

Question 15

define herd immunity

Answer 15

where unvaccinated people are protected because occurrence of a disease is reduced by number of people who are vaccinated.

Question 16

4 differences between active and passive immunity

Answer 16

1 active involves memory cells, passive does not
2 active involves production of antibodies by plasma cells
3 passive is short term because antibody is broken down, active is long term because antibodies produced in response to antigen
4 active takes time to develop, passive is fast acting

Question 17

how do vaccines work

Answer 17

1 vaccine contains antigens from pathogen
2 macrophage presents antigens on surface of cell
3 t cell with complementary receptor proteins binds to antigen
4 t cell stimulates b cells with complementary antibodies to divide by mitosis and form clones
5 plasma cells secrete antibodies specific to the pathogens antigens
6 b cell secretes large amounts of antibody

Question 18

define monoclonal antibody

Answer 18

a single desired type of antibody
B cell isolated and cloned
all have same tertiary structure

Question 19

what are monoclonal antibodies used to do

Answer 19

target specific cells and substances, diagnose disease and in pregnancy testing.

Question 20

how does indirect monoclonal antibody therapy work

Answer 20

cytotoxic/radioactive drug attached to monoclonal antibody. when MA attaches to the target cell it kills the cell.

Question 21

how does pregnancy testing work

Answer 21

MA bind to HCG hormone tiny amounts of the hormone are passed out of the body in urine and this is picked up by the MAs.

Question 22

3 ethical issues of monoclonal antibodies

Answer 22

• involves deliberately inducing cancer in mice
• have been some deaths associated with MA use
• drug trials of new drugs using MAs has caused harm in the past

Question 23

what does the eliza test do

Answer 23

enables you to see if a patient has a particular antibody to a certain antigen.

Question 24

how does the eliza test work

Answer 24

1 antigen is adsorbed to well
2 patient serum is added, complimentary antibody binds to antigen (wash out)
3 enzyme linked antiHISG is added and binds to bound antibody (wash out)
4 enzyme substrate is added and reaction produces a product that causes a visible colour change

Question 25

list the structure/parts of a HIV virus

Answer 25

genetic material RNA attachment protein capsid lipid envelope matrix reverse transcriptase enzyme

Question 26

how does HIV cause the symptoms of AIDs

Answer 26

1 kills/interferes with normal functioning of helper t cells 2 body cannot produce adequate numbers of b cells to produce antibodies or Tc cells to kill infected cells 3 immune response is reduced and is more susceptible to infections and cancer

Question 27

describe how HIV is replicated (5 marks)

Answer 27

attatchment proteins attach to receptors on helper T cell RNA enters cell reverse transcriptase converts RNA to DNA viral proteins produced virus assembled and released from cell

Question 28

how is HIV replicated once INSIDE helper T cell (4 marks)

Answer 28

RNA converted into DNA using reverse transcriptase DNA inserted DNA transcribed into RNA RNA translated into viral proteins

Question 29

Describe how a phagocyte destroys a pathogen present in the blood (3 marks)

Answer 29

engulfs forms phagosome and fuses with lysosome lysozymes hydrolyse

Question 30

describe and explain the role of antibodies in stimulating phagocytosis (2 marks)

Answer 30

binds to antigen antibodies cause agglutination