Immunity

Question 1

Why do the levels of antibodies not return to zero after the primary response?

Answer 1

Memory cells remain in the blood ready for reinfection

Question 2

How to pathogens evade the immune system?

Answer 2

Pathogens can exchange plasmids to change their genes which will code for different proteins and therefore different antigens.

The body no longer has the memory cells for those antigens so must go through the slower primary response again and the host will become ill.

Question 3

Draw the structure of an antibody including key words.

Answer 3

Light chan
Heavy chain
Disulfide bridges
Variable and constant region

Question 4

Why are vaccines given as injections?

Answer 4

So that the proteins are not broken down by enzymes before entering the immune system.

Question 5

Why is the secondary response factor than a primary response?

Answer 5

In a primary response the immune system has to undergo clonal selection and produce plasma cells

The secondary response already has memory cells which can activate plasma cells to produce antibodies quickly.

Question 6

Explain active immunity and give 2 examples

Answer 6

When the immune system makes antibodies through the immune response

Getting ill and having a vaccination containing weekend or dead pathogens

Question 7

How do vaccinations cause herd immunity

Answer 7

When a large enough population is vaccinated the frequency of the pathogen decreases and those not vaccinated are surrounded by vaccinated people so are less likely to contract the pathogen

Question 8

Explain the difference between humoral and cellular response.

Answer 8

Humoral is the clonal selection of B cells to produce monoclonal antibodies

Cellular is the T cells and other immune system cells that are not specific eg phagocytes

Question 9

Explain passive immunity and give two examples

Answer 9

Given the antibodies so there is no immune response

Antibodies in the placenta and breast milk and an injection of antibodies so the body doesn’t need to make them in an immune response.

Question 10

Describe the process of phagocytosis in 6 steps…..

Answer 10

1. phagocyte recognises foreign antigen on pathogen
2. Pathogen is ENGULFED by the phagocyte
3. Pathogen is contained within PHAGOCYTIC VACUOLE in the cytoplasm of the phagocyte
4. LYSOSOMES FUSE with the phagocytic vacuole and release LYSOZYMES which break down the pathogen
5. Phagocyte presents PATHOGENS ANTIGENS on it’s surface to activate immune response
6. Phagocyte activates T cells

Question 11

Why are antibodies specific?

Answer 11

Antibodies are proteins with a variable region that has a specific tertiary structure which make it complementary to the antigen

Question 12

Describe the immune response after phagocytosis….

Answer 12

1. Phagocyte actives COMPLEMENTARY T CELLS
2. T CELLS bind to antigens on the surface of the pathogen
3. HELPER T CELLS release chemical signals which activate CYTOTOXIC T CELLS which destroy foreign antibodies
4. B CELLS are activated by HELPER T CELLS
5. B CELLS divide by CLONAL SELECTION into plasma cells which release COMPLIMENTARY ANTIBODIES.
6. Antibodies bind with antigens causing AGGLUTINATION which disables pathogens so CYTOTOXIC T CELLS can destroy pathogen.
7. B cells divide into MEMORY CELLS. Which remain in the blood for a SECONDARY RESPONSE.