the immune system

Question 1

foreign antigens trigger an immune response

Answer 1

• antigens are molecules that generate an immune response when detected by the body
• usually found on the surface of cells

Question 2

what do antigens do

Answer 2

used by the immune system to identify pathogens, abnormal body cells, and toxins

Question 3

explain how phagocytes engulf pathogens

Answer 3

• a phagocyte recognises the foreign antigens on the pathogens
• the cytoplasm of the phagocyte moves around the pathogen engulfing it
• pathogen now contained in a phagocytic vacuole in the cytoplasm of the phagocyte
• a lysosome fuses with the phagocytic vacuole and the lysozymes break down the pathogen
• phagocyte then presents the pathogens antigens- it sticks the antigens on the surface to activate other immune system cells

Question 4

explain how phagocytes activate T-cells/ T- lymphocytes

Answer 4

• T cells have receptor proteins on the surface that binds to complimentary antigens presented by phagocytes
• this activates the t cell
• t helper cells release chemical signals which activate and stimulate phagocytosis
• t helper cells also activate b cells
• t killer cells kill abnormal and foreign cells

Question 5

what do t helper cells do

Answer 5

• t helper cells release chemical signals which activate and stimulate phagocytosis
• t helper cells also activate b cells

Question 6

what do t killer cells do

Answer 6

t killer cells kill abnormal and foreign cells

Question 7

what do b cells do and how do they divide into plasma cells

Answer 7

• when the antibody on the surface of a b cell meets a complimentary shaped antigen it binds to it
• this together with the substances released from t helper cells activates the b cell
• this process is called clonal selection
• the activated B cells divides into plasma cells

Question 8

explain how plasma cells make more antibodies to a specific antigen

Answer 8

• plasma cells are identical to b cells
• they secrete loads of antibodies specific to the antigen
  these are monoclonal antibodies
• they bind to the antigens on the surface of the pathogen to form lots of antibody-antigen complexes

Question 9

features of antibodies binding sites

Answer 9

• an antibody has two binding sites meaning it can bind to two pathogens at the same time

Question 10

what is agglunation

Answer 10

when pathogens bind to antibodies and the pathogens clump together

Question 11

draw antibody bound with antigen

Answer 11

textbook page 46

Question 12

explain antibody structure

Answer 12

• antibodies are proteins
• theyre made up of chains of amino acids
• the specificity of an antibody depends on its variable regions which form antigen binding sites
• each antibody has a variable region with a unique tertiary structure making it complimentary to a specific antigen
• ## all antibodies have the same constant regions

Question 13

what is the cellular immune response

Answer 13

the T cells and other immune system cells that they interact with e.g. phagocytes form the cellular response

Question 14

what is the humoral immune response

Answer 14

B cells, clonal selection and the production of monoclonal antibodies form the humoral response

Question 15

primary immune response

Answer 15

• antigen enters body for the first time
• primary response is slow due to lack of b cells
• patient will show some symptoms of the disease
  -b cells and t cells both make memory cells which stay in the body for a long time
• the person is now immune

Question 16

what is secondary immune response

Answer 16

• same pathogen enters the body and the immune system has a faster stronger response
• clonal selection happens faster
• memory B cells are activated and divide into plasma cells that produce the right antibody
• memory t cells are activated and divide into the correct type of t cells to kill the cell that carries the antigen
• secondary response often gets rid of pathogen before symptoms are shown