unit 2, antibodies and monoclonal anitbodies

Question 1

what are antibodies made up of?

Answer 1

-protiens
-4 polypeptide chains (quaternary structure)
-2 heavy and 2 light chains

Question 2

what are the chains connected by?

Answer 2

disulfide bridges

Question 3

what is the constant region?

Answer 3

-allow them to bind to receptors on immune system cells
-they are the same in every antibody

Question 4

what is the variable region?

Answer 4

-antigen binding sites
-unique tertiary structure that is complementary to an antigen

Question 5

how many variable regions do they have?

Answer 5

2

Question 6

how many pathogens can one antibody bind to at once?

Answer 6

2

Question 7

what is agglutination?

Answer 7

antibodies bind to antigens to clump them together, making it easier for phagocytosis to happen and destroy more bacteria at one time

Question 8

what are neutralising toxins?

Answer 8

some antibodies work by neutralsing toxins that are released by the pathogens

Question 9

how do antibodies prevent viruses from entering host cells?

Answer 9

viruses have spike proteins on their surface which recognise and bind to host cells- allowing them entry. antibodies bind to these viruses preventing them joining to host cells.

Question 10

what is antigenic variation?

Answer 10

some pathognens can form different strains, which is caused by mutations in genetic material

Question 11

what does antigenic variation result in?

Answer 11

If you are reinfected a second time the memory cells will not recognise the antigen and wont be activated. The antibodies made last time are no longer complememtnary. So primary response happens has to start again.

Question 12

what forms the shape of the antigen binding site?

Answer 12

primary sequence of amino acids at binding site is specific to form it

Question 13

what markscheme words should always be included in your answers?

Answer 13

• tertiary structure that is complementary to the antigen
  -specific primary sequence of amino acids
  -complementary bidning site
  -antigen antibody complex
  -destroy bacteria , DO NOT USE ATTACK

Question 14

what are monoclonal antibodies?

Answer 14

• they are artificially derived from a single B cell clone
  -it is a way of producing lots and lots of the same antibody

Question 15

how are monoclonal antibodies collected?

Answer 15

• an antigen is injected into a mouse
  -the mouses spleen is then removed
  -the plasma cells form the spleen are then fused (hybridised) with tumour cells to form hybridoma
• this produces/forms an monoclonal antibody and is produced in large quantities.

Question 16

what is the process of the direct ELISA test?

Answer 16

-antigens from a patient sample are bound to a well
-antibody that is conjugated with an enzyme added, they are complementary to the antigen so they will bind
-the well is washed to remove any unbound antibodies
-substrate is added, if there is a colour change then there are antigens present as the bind has been successful

Question 17

what happens if the well is not washed to remove any unbound antibodies?

Answer 17

a false positive would be the result as the substrate will identify the antibody and change colour, even if there are no antigens present

Question 18

what is the process of the indirect ELISA? Use example of testing for HIV.

Answer 18

• a HIV antigen is bound to the bottom of well on a well plate
• a sample of blood plasma is added to the well from the patient, this is because there are antibodies here. if there are antibodies complementary to the antigen then they will bind
  -well is washed to remove any unbound antibodies
  -a secondary antibody is then added to the well that has a specific enzyme attached to it, this binds to the antibody form the blood plasma
  -well is washed again to remove and unattached antibodies
• a solution containing substrate is then added, if there is a colour change then the person is infected with HIV

Question 19

what happens if there is no first antibody in indirect ELISA?

Answer 19

secondary antibody can not bind

Question 20

what hormone does the placenta produce if a woman is pregnant, and where is it found?

Answer 20

HGC, it is found in urine

Question 21

how does a pregnancy test work?

Answer 21

• when urine goes on a stick, the HCG protein antigen binds to the antibodies that are specific forming an antigen antibody complex.
• this causes the dye enzyme that is attached to the antibody specific to HCG to change colour

Question 22

why does the control site sometimes have no line on a pregnancy test?

Answer 22

A HCG antigen sometimes binds to the control site also, this prevents the control site changing colour to form a line because it blocks the antigen and antibody complex.

Question 23

reasons for monoclonal antibodies

Answer 23

• cheaper to develop than conventional drugs because it is based on tested technology.
  -due to them having specific binding sites they target specific cells, biding to specific diseased cells, therefore not damaging non-diseased cells unlike other treatments.
  -treat a wide range of diseases
  -many different applications for using them

Question 24

reasons against monoclonal antibodies

Answer 24

-may cause side effects
-research, developing, testing are expensive
-time consuming process
-difficult to get the right antibody and attach a compound to it
-mice are used, and tests are taken to determine the side effects