The Immune System 2C

Question 1

What is an antigen

Answer 1

molecules (usually proteins) that generate an immune response when detected by the body

Question 2

Where are antigens found

Answer 2

surface of cells

Question 3

What are antigens used for

Answer 3

Used by immune system to identify pathogen, abnormal body cells, toxins and cells from other individuals of the same species eg organ transplants

Question 4

What is a phagocyte

Answer 4

a type of white blood cell which carries out phagocytosis they are found in in the blood and are in tissues

Question 5

How do phagocytes work

Answer 5

1. A phagocyte recognises the foreign antigen on a pathogen
2. Cytoplasm of the phagocyte moves round the pathogen, engulfing it
3. The pathogen in now contained in a phagocytic vacuole in the cytoplasm of the phagocyte
4. A lysosome fuses with the phagocytic vacuole. The lysozymes break down the pathogen
5. The phagocyte then presents the pathogen’s antigens - it sticks the antigens on its surface to activate other immune system cells

Question 6

What do phagocytes active

Answer 6

T-Cells

Question 7

What is a T Cell

Answer 7

A type of white blood cell

Question 8

What do receptor proteins on T cells do

Answer 8

Bind to complementary antigens presented to it by phagocytes

Question 9

What do helper T cells do

Answer 9

Release chemical signals that activate and stimulate phagocytes. They can also activate B cells

Question 10

What do cytotoxic T cells do

Answer 10

They kill abnormal and foreign cells

Question 11

What are B cells

Answer 11

A type of white blood cell

Question 12

What are B cells covered with

Answer 12

antibodies. Each B cell has a different shaped antibody on its membrane , so different ones bind to different shaped antigens

Question 13

What are antibodies

Answer 13

Proteins which bind antigens to form an antigen antibody complex. Made
up of chains of amino acids. Each antibody has a different variable region with a different tertiary structure All antibodies have the same constant regions

Question 14

Describe clonal selection

Answer 14

when an antigen- antibody complex is formed and the substances released from helper T cells activates the B cell. This activated B cell divides into plasma cells

Question 15

What do you call two cells that are identical to each other

Answer 15

clones. For example, plasma cells and B cells are clones

Question 16

How many binding sites does an antibody have

Answer 16

2, so an antibody can bind to two pathogens at once

Question 17

Define agglutination

Answer 17

when pathogens become clumped together phagocytes then bind to the antibodies and phagocytose many pathogens at once this leads to the destruction of pathogen carrying this antigen in the body

Question 18

Define Cellular immune response

Answer 18

The T - cells and other immune system cells they interact with.

Question 19

Define Humoral immune response

Answer 19

B-cells, clonal selection and the production of monoclonal antibodies

Question 20

The primary immune response

Answer 20

When an antigen enters the body for a first time
Not many B cells that can make the antibody need to bind to the antigen, eventually the body will produce enough of the right antibody to overcome the infection. Meanwhile, the person will show symptoms
After being exposed to the antigen both T- cells and B- cells produce memory cells which remain in the body for a long time. Memory T- cells remember the specific antigen and will recognise it a second time. Memory B- cells record the specific antibodies needed to bind the antigen
The person is now immune - their immune system has the ability to respond quickly to a second infection

Question 21

Secondary immune response

Answer 21

Same pathogen enters the body again and the immune response is quicker.
Clonal selection happens faster. Memory B- cells are activated and divide into plasma cells that produce the right antibody to the antigen. Memory T- are activated and divide into the correct type of T- cells to kill the cell carrying the antigen
The secondary response often gets rid of the pathogen before you begin to show any symptoms - you are immune to the pathogen