save my exams -cell recohnition and immunity

Question 1

several defence mechanisms against pathogens

Answer 1

-physical and chemical defences
-Inflammation
-Recognising ‘foreign’ cells

Question 2

-physical and chemical defences

Answer 2

such as the skin, mucous membranes, tears (containing the enzyme lysozyme, which destroys bacteria) and saliva

Question 3

Inflammation

Answer 3

swelling and heating) of the region invaded by the pathogen, a process known as a non-specific inflammatory response

Question 4

Recognising ‘foreign’ cells

Answer 4

targeting any pathogenic cells, a process known as a specific immune response

Question 5

how the ability to recognise ‘foreign’ cells is made possible

Answer 5

-specific molecules found on the surface of cells
-enable them to be identified by the body
-usually proteins-part of the phospholipid bilayer, such as glycoprotein

Question 6

surface proteins are found on (and enable the body to recognise) the following:

Answer 6

Pathogenic cells
Abnormal body cells, such as cancerous or pathogen-infected cells
Toxins
Cells from other individuals from the same species

Question 7

organ transplants to occur successfully

Answer 7

the body must not recognise the cells and tissues of the donated organ as foreign, so that no immune response occurs)

Question 8

antigens

Answer 8

the surface molecules used by the body to identify cells, viral particles and toxins

Question 9

An example of the importance of antigens in defending against pathogens

Answer 9

White blood cells known as phagocytes have surface proteins that act as receptors and bind to the proteins (antigens) on the surface of pathogens
This enables pathogens to be engulfed and digested
The antigens that were found on the pathogen can then be presented on the surface of the phagocyte (now an antigen-presenting cell)
This is then used to recruit other cells of the immune system, leading to a specific immune response

Question 10

where are antigens found

Answer 10

cell surface membranes, bacterial cell walls, or the surfaces of viruses
Some glycolipids and glycoproteins on the outer surface of cell surface membranes act as antigens

Question 11

Antigens can be either

Answer 11

self antigens or non-self antigens

Question 12

self antigens

Answer 12

Antigens produced by the organism’s own body cells (those that the immune system does not recognise as foreign antigens)
do not stimulate an immune response

Question 13

non self antigens

Answer 13

not produced by the organism’s own body cells (those that the immune system recognises as being foreign
stimulate an immune response

Question 14

Some pathogens exhibit antigen variability

Answer 14

The antigens present on their surface change frequently due to genetic mutations

Question 15

antigen variability problem

Answer 15

-surface receptors on lymphocytes and memory cells are complementary in shape to only one antigen
-When the antigen on a pathogen changes the lymphocytes and memory cells can no longer bind
-As a result, there is no secondary immune response
The host gets infected and suffers from the disease again

Question 16

Phagocytes

Answer 16

white blood cells that are produced continuously in the bone marrow before being distributed around the body in the blood
non-specific immune response

Question 17

two main types of phagocyte

Answer 17

Neutrophils
Macrophages

Question 18

Neutrophils

Answer 18

During an infection, they are released in large numbers
short-lived cells
Chemicals released by pathogens attract neutrophils to the site where the pathogens are located- chemotaxis
move towards pathogen
trigger to stimulate neutrophils to attack the pathogens
receptor proteins recognise antibody molecules and attach to them
cell surface membrane of a neutrophil extends out and around the pathogen, engulfing it
endocytosis

Question 19

lysosomes

Answer 19

membrane organelles that contain digestive enzymes called lysozymes
These enzymes digest unwanted material present in cells

Question 20

phagosome

Answer 20

phagocytic vacuole formed around a pathogen once it has been engulfed by a neutrophil

Question 21

phagolysosome

Answer 21

A lysosome fuses with the membrane of the phagosome
releases lysozymes
digest the pathogen
These digestive enzymes destroy the pathogen

Question 22

Pus

Answer 22

sign of dead neutrophils
After killing and digesting the pathogens, the neutrophils die

Question 23

macrophage

Answer 23

larger than neutrophils and are long-lived cells
move into organs
produced in the bone marrow,travel in the blood as monocytes
then develop into macrophages once they leave the blood

Question 24

mode of action of macrophage

Answer 24

carry out phagocytosis in a similar way to neutrophils, they do not destroy pathogens completely
can display the antigens of the pathogens on their surface
These displayed antigens can then be recognised by lymphocytes

Question 25

Lymphocytes

Answer 25

type of white blood cell specific immune response smaller than phagocytes produced in the bone marrow before birth T-lymphocytes (T cells) B-lymphocytes (B cells)

Question 26

immature t lymphocytes

Answer 26

leave the bone marrow to mature in the thymus

Question 27

Mature T-lymphocytes

Answer 27

have specific cell surface receptors called T cell receptors activated when they encounter their specific antigen might be a macrophage or a body cell that has been invaded by a pathogen

Question 28

two types of t lymphocytes

Answer 28

helper T cells cytotoxic T cells

Question 29

release cytokines which stimulate:

Answer 29

maturation of B-lymphocytes into antibody-secreting plasma cells production of memory B cells activation of cytotoxic T cells, increased rate of phagocytosis

Question 30

role of t helper cells

Answer 30

assist other white blood cells in the immune response release cytokines The production of memory B cells The activation of cytotoxic T cells, which destroy virus infected cells and tumour cells An increased rate of phagocytosis

Question 31

increased rate of phagocytosis

Answer 31

destroy virus infected cells and tumour cells

Question 32

B lymphocytes

Answer 32

humoral immune response remain in the bone marrow until they are mature mature the genes coding for antibodies each type of B-lymphocyte cell can make one type of antibody molecule Part of each antibody molecule forms a glycoprotein receptor that can combine specifically with one type of antigen If that antigen enters the body, B-lymphocyte cells with the correct cell surface receptors will be able to recognise it and bind to it (clonal selection) These specific B-lymphocytes divide repeatedly by mitosis (clonal expansion) and differentiate into two main types of cell: Plasma cells Memory cells active B cells to divide stimulate phagocytosis activate cytotoxin T cells

Question 33

cytotoxic T cellstol

Question 34

What is an antigen-presenting cell

Answer 34

An antigen-presenting cell is one of the host's cells that has been invaded by a pathogen and is displaying the antigen on its cell surface membrane

Question 35

What does an antigen-presenting cell do

Answer 35

These cells present the antigens from toxins, foreign cells and ingested pathogens They help to recruit other cells of the immune system to produce a specific immune response Once the surface receptor of the T cell binds to the specific complementary antigen (on the antigen-presenting cell) it becomes sensitised and starts dividing to produce a clone of cells

Question 36

What are the antigen-presenting cells?

Answer 36

Several different immune system cells can present antigens The most common types are macrophages and dendritic cells Although less common, neutrophils can also act as antigen-presenting cells

Question 37

what does hiv stand for

Answer 37

human immunodeficiency virus

Question 38

AIDS

Answer 38

acquired immune deficiency syndrome

Answer 39

t helper cells stimulate cytokimens and b cells release antibodies and things that protect the body so if t helper cells damaged by hiv then body cannot be protected

Question 41

hiv -invasion of t helper cells

Answer 41

1)the virus binds to the receptors on the cell surface membrane 2)the virus envelope fuses with the cell