cell recognition & the immune system

Question 1

pathogen =

Answer 1

microorganism that causes a disease (& immune response)
> eg. virus, bacteria

Question 2

cell recognition

Answer 2

• every cell has specific molecules on its surface membrane
• can be identified
• self/ non-self cells

Question 3

antigen =

Answer 3

foreign protein that stimulates an I.R

Question 4

antibody =

Answer 4

protein specific to an antigen, produced by B cells

Question 5

struc. of antibody

Answer 5

• quaternary struc (2 polypeptides)
• variable region (comple. to antigen)
• light chain & heavy chain
• hinge region
• disulfide bonds join 2 diff. polypeptides

Question 6

antigen variability

Answer 6

• mutation of DNA
• altered tertiary struc. of antigen
• it can bind to receptors of other species
• memory cells no longer comple. to antigen

Question 7

capsid variability

Answer 7

• mutation of RNA
• altered tertiary struc. of viral attachment protein
• it can bind to receptors of other species

Question 8

types of cells that can stimulate an I.R (immune response)

Answer 8

• pathogens
• cancer/tumour cells
• cells from other organisms/transplants
• self-cells if infected by virus

Question 9

phagocytes

Answer 9

• large, white blood cells
• engulf & remove dead/invading pathogens

Question 10

the 2 types of phagocytes

Answer 10

• macrophages
• neutrophils

Question 11

neutrophils

Answer 11

• rapid reaction force
• lobed nucleus to squeeze through capillaries

Question 12

process of phagocytosis

Answer 12

1.phagocyte binds to antigen
2.cytoplasm of the phagocyte engulfs the pathogen
3.this forms a phagosome vesicle which fuses with lysosomes
4.lysozymes digest the pathogen
5.antigen from pathogen displayed on cell-membrane

Question 13

the 2 types of lymphocytes

Answer 13

• T cells
• B cells

Question 14

T cells

Answer 14

• mature in thymus gland

Question 15

B cells

Answer 15

• mature in bone marrow

Question 16

the specific, cell-mediated response
(role of T cells)

Answer 16

1) Helper T cell binds to antigen displayed on the phagocyte
2) Helper T cell releases cytokines
3) cytokines stimulates killer T cells & specific B cell (clonal selection)

Question 17

the humoural response
(role of B cells)

Answer 17

1) antibody on surface of activated B cell binds to comple. antigen
2) B cell divides by mitosis to make plasma cells
3) plasma cells produce antibodies
4) some plasma cells release monoclonal antibodies

Question 18

monoclonal antibodies =

Answer 18

antibodies with same tertiary struc, made by identical B cells specific to one antigen

Question 19

function of monoclonal antibodies

Answer 19

• carries drugs to specific cells
• blocks receptors on cells

Question 20

vaccine =

Answer 20

injection of antigens from a pathogen which stimulates the production of antibodies

Question 21

process of vaccination

Answer 21

1) injection of antigens from pathogen
2) describe specific, cellular response
3) describe humoural response

Question 22

antigen + antibody =

Answer 22

antigen-antibody complex
—> effects of this formation:
* bacterial cells can agglutinate —> destroyed via phagocytosis
* can neutralise toxins

Question 23

differences between active & passive immunity

Answer 23

1) active involves memory cells, passive doesn’t
2) active involves production of antibody by plasma cells, passive involves antibody introduced into body from outside
3) active = long term —> antibody produced in response to antigen, passive = short term —> antibody broken down

Question 24

HIV struc

Answer 24

• attachment proteins
• round lipid envelope
• capsid
• RNA
• reverse transcriptase

Question 25

process of *HIV replication*

Answer 25

1) attachment proteins attach to **receptors** on helper T cell 2) RNA enters cell 3) **reverse transcriptase** converts RNA to DNA 4) viral protein prod. from DNA 5) virus particles assembled & released

Question 26

effect of HIV on immune system

Answer 26

- HIV **destroys** helper T cell - **fewer** B cells form plasma cells - less antibodies prod. - inability to fight off opportunistic infections

Question 27

why are antibiotics ineffective against viruses?

Answer 27

viruses are inside cells where antibiotics can’t reach

Question 28

methods of analysing viral DNA

Answer 28

* genetic fingerprinting * genome sequencing

Question 29

developing vaccines against viruses

Answer 29

* identify **viral proteins** from genetic code * identify potential antigens to use in vaccines

Question 30

ELISA test

Answer 30

1) first antigen attaches to pathogen 2) wash to **remove** unattached antibody 3) second antibody **w enzyme attached** is added 4) second antibody attaches to antigen 5) **substrate** added —> **colour** change for positive result

Question 31

why is a control well used?

Answer 31

* ensures that **only** the enzyme causes colour change * all **unattached** antibodies **washed** away

Question 32

role of antibodies in producing +ve result in ELISA test

Answer 32

* 1st antibody binds with immobilised antigen attached to well * 2nd antibody w attached enzyme is added —> binds w substrate * colour change occurs

Question 33

why is the ELISA test specific?

Answer 33

* antibody has **tertiary** struc. * comple. to **binding** site on antigen