🩶 3.2.4 Cell Recognition And The Immune System

Question 1

Define antigen

Answer 1

Glycoprotein capable of stimulating an immune response

Question 2

Define phagocyte

Answer 2

A white blood cell which engulfs foreign antigens and presents them

Question 3

Define helper t cell

Answer 3

Stimulates phagocytosis, cytotoxic T cells, B cells and it is also part of the cellular response

Question 4

Define cytotoxic T cell

Answer 4

Part of the cellular response and they destroy pathogens directly (cell to cell)

Question 5

Define plasma B cells

Answer 5

It is part of the humoral response and they produce antibodies and release them into the blood

Question 6

Define antibody

Answer 6

A quaternary protein with four polypeptide chains. It is produced in response to a foreign antigen – and it produces antigen antibody complexes

Question 7

Define monoclonal antibody

Answer 7

It is produced by genetically identical plasma B cells

Question 8

Define memory B cells

Answer 8

Retained in the blood for long periods of time. On exposure to the same antigen, they are converted to plasma B cells and produce antibodies.

Question 9

Define agglutination

Answer 9

Where the antibodies are bound to other pathogens antigens causing the pathogens to clump. This facilitates phagocytosis.

Question 10

What are the four types of antigens in the body considered to be foreign?

Answer 10

1- toxins
2- pathogens
3- tissue organs
4- abnormal cells

Question 11

How are toxins considered foreign?

Answer 11

They themselves are antigens

Question 12

How are pathogens considered foreign ?

Answer 12

They are disease forming microorganisms i.e. bacteria, fungi, viruses all have foreign antigens on them

Question 13

How are tissue organs considered to be foreign?

Answer 13

These are tissue organs from members of the same species for example, mammals tissue organs in other mammal tissue organs

Question 14

How are abnormal cells considered foreign?

Answer 14

These are cells including cancer cells

Question 15

What is the first stage of the immune response called and what is it carried out by?

Answer 15

The first stage of the immune response is called phagocytosis and it is carried out by phagocytes which are a type of white blood cell

Question 16

Describe the method of phagocytosis

Answer 16

1- phagocytes recognise antigen as foreign
2- phagocytes extends cell membrane and engulfs the pathogen
3- pathogen enters a phagocytic vacuole
4- lysosomes fuse to vacuole
5- lysosomes secretes lysozyme into phagocytic vacuole which hydrolyses the pathogen
6- the antigen is presented on the cell membrane

Question 17

What is the second stage of the immune response?

Answer 17

The cellular response is the second stage of the immune response

Question 18

Describe the cellular response

Answer 18

• receptor proteins on a specific T cell are complementary to the antigens presented by the phagocyte
• binds to activate T cell
• divides using mitosis to produce many identical clones
• T cells differentiate into helper T cells and cytotoxic T cells
• helper T cells stimulate phagocytosis, B cells and cytotoxic T cells
• cytotoxic T cells bind directly to the pathogen and release toxic substances and enzymes that pierce holes in the cell wall and membrane and destroy the pathogens

Question 19

What is the function of plasma B cells ?

Answer 19

• To produce identical antibodies (monoclonal) which are specific to complementary antigens on the pathogen
• The antibodies are released into the blood where they bind to the antigens on the pathogens causing agglutination (clumping)
• this immobilisers the pathogens, allowing the phagocytes to engulf and destroy them

Question 20

What is the function of memory B cells?

Answer 20

• they are retained in the blood
• they are covered in specific protein receptors that are complementary to pathogens antigen
• if they encounter antigen again, they differentiate and divide by mitosis into plasma cells and makes more antibodies

Question 21

What response comes after the cellular response ?

Answer 21

The humoral response

Question 22

Describe the method of the humoral response

Answer 22

1- specific receptor proteins (antibodies) of B lymphocytes are complementary to antigen presented by phagocyte
2- these bind, and as the t helper cell also stimulates B cells they are activated
3- they divide using mitosis to produce many identical clones
4- clonal selection producing (monoclonal antibodies)
5- B cells differentiate into plasma B cells and memory B cells

Question 23

Describe the structure of an antibody

Answer 23

• quaternary protein
• produced by plasma B cells
• heavy and light chains
• disulphide bridges join chains
• constant and variable regions (binding site)
• variable region specific to complementary antigen (due to tertiary structure) - it is the same for all monoclonal antibodies - from the the same plasma B cells
• form antigen antibody complexes causing agglutination (clumping) facilitating phagocytosis

Question 24

What is a vaccination?

Answer 24

• A vaccination contains a dead or inactive / weakened form of the pathogen but always contains its antigens
• causes the body to make memory cells against a pathogen without the pathogen causing the actual disease

Question 25

What is herd immunity?

Answer 25

In a community where most people have been vaccinated, those not vaccinated are less likely to catch the disease as there are fewer people to catch it from

Question 26

What are some ethical concerns of vaccinations?

Answer 26

- animal testing is unethical/issues with animal welfare - Animal products used in vaccines can be against peoples ethical beliefs/religion - Reliance on her immunity i.e not being vaccinated yourself - ethics of who is chosen to be vaccinated first

Question 27

There are four different types of immunity. What are they ?

Answer 27

- Active natural - Active artificial - passive natural - passive artificial