2C Immune System

Question 1

What is an antigen?

Answer 1

Protein on the surface of cells that can trigger an immune response.

Question 2

What types of antigens can trigger an immune response?

Answer 2

Pathogens, abnormal body cells, toxins, cells from others in the same species

Question 3

How do pathogens trigger and immune response?

Answer 3

They are identified as foreign and the immune system responds to destroy them

Question 4

How do abnormal body cells trigger an immune response?

Answer 4

Cancerous/pathogen infected cells that display abnormal antigens

Question 5

How to toxins trigger an immune response?

Answer 5

These are molecules that are poisonous -the immunes system responds to both toxins and pathogens that release them

Question 6

How do cells from organisms of the same species trigger an immune response?

Answer 6

They display different antigens to your own and so can trigger an immune response as their proteins are recognised as foreign.
This type of response is responsible for the rejection of donated blood/transplanted organs

Question 7

What is a phagocyte?

Answer 7

A type of WBC that can engulf pathogens in the process of phagocytosis

Question 8

Is phagocytosis specific or non-specific and why?

Answer 8

Non-specific because it doesn’t distinguish between pathogens

Question 9

Describe the process of phagocytosis.

Answer 9

> Pathogens release chemicals which act as ATTRACTANTS for the phagocytes
A phagocyte recognises a FOREIGN ANTIGEN and moves along its CONCENTRATION GRADIENT towards it
It BINDS to the pathogen and its CYTOPLASM fuses around it to form a VESICLE called a PHAGOSOME
LYSOSOMES move towards the phagosome and fuse with it
they release LYSOZYME which HYDROLYSE the pathogen’s membrane causing it to release it’s contents
SOLUBLE products are ABSORBED and and antigen is presented on the surface of the phagocyte = ANTIGEN-PRESENTING CELL
This ACTIVATES the response of other immune system cells

Question 10

Describe the process of cell mediated immunity.

Answer 10

> T CELLS have RECEPTOR PROTEINS that bind to COMPLIMENTARY ANTIGENS presented by phagocytosis
T HELPER CELLS with complementary receptors to the shape of the antigen being presented are ACTIVATED and bind to it
This activates other T cells to divide by MITOSIS to produce other cells with complementary receptors (CYTOTOXIC CELLS and MEMORY CELLS)
it also STIMULATES B CELLS and further phagocytosis

Question 11

Is cell-mediated immunity specific or non-specific and why?

Answer 11

Specific as it can only respond with cells that have specific complementary receptors to the shape of the antigen

Question 12

Which type of immune response uses T cells?

Answer 12

Cell-mediated

Question 13

Where do T cells mature?

Answer 13

In the Thymus gland

Question 14

Is Humoral immunity specific or non-specific and why?

Answer 14

Specific as it can only respond with cells that have complementary receptors to the shape of the antigen

Question 15

How are B cells adapted to their function?

Answer 15

They are covered with antibodies on their CSM that have specific binding sites that are complementary to certain antigens

Question 16

Describe the process of humoral immunity.

Answer 16

> complementary antibodies can bind to antigens to form ANTIGEN-ANTIBODY COMPLEXES
This binding can stimulate the MITOSIS of B cells into MEMORY and PLASMA cells which provide SHORT and LONG TERM immunity against the antigen

Question 17

Describe the structure of antibodies.

Answer 17

> Antibodies are PROTEINS and their specificity depends on their VARIABLE REGION which has a specific TERTIARY structure as a result of their PRIMARY AMINO ACID sequence
This forms the ANTIGEN BINDING SITE
all antibodies have the same CONSTANT REGIONS
They are made up of 2 LIGHT and 2 HEAVY CHAINS
A DISULPHIDE BRIDGE between the 2 HEAVY chains in the constant region binds the chains together

Question 18

Describe what the secondary immune response is and explain how it works.

Answer 18

> if the body is REINFECTED by the SAME pathogen again, the response will be QUICKER and STRONGER
MEMORY B CELLS are ACTIVATED and divide into PLASMA CELLS that produce the COMPLEMENTARY antibody to the antigen
MEMORY T CELLS are ACTIVATED and divide into CYTOTOXIC CELLS that can kill the pathogen
This helps to destroy the pathogen before symptoms of a disease can show