[OLD] The Immune System

Question 1

what is a pathogeN?

Answer 1

a microorganism that causes disease e.g virus, bacteria, fungus

Question 2

what is the body’s first line of defence?

Answer 2

tears
skin
large intestine
saliva
respiratory tract 
bladder
stomach
earwax

Question 3

what is an antigen?

Answer 3

a molecule that triggers an immune response

always large complex molecules

Question 4

what is an antibody?

Answer 4

a protein which binds to antigens, they are specific

Question 5

what are antibodies made by?

Answer 5

white blood cells

Question 6

what is a toxin?

Answer 6

a substance released by pathogens, they are toxic

Question 7

what do antitoxins do?

Answer 7

neutralise toxins

Question 8

what makes antitoxins?

Answer 8

white blood cells

Question 9

what is an antibiotic?

Answer 9

a substance that kills bacteria or prevents its growth

Question 10

describe phagocytosis

Answer 10

pathogens release chemical products that attract phagocytes
the phagocyte engulfs the pathogen in a phagosome
the phagosome fuses with a lysosome already within the phagocyte to form a phagolysome
lysosyme from the lysosome is released which hydrolysed the pathogen, breaking it down
debris is released by exocytosis

Question 11

Why do mutations cause antibiotic resistance?

Answer 11

If you Change the DNA sequence resulting in a different amino acid, the shape of the protein i.e the tertiary structure will change, giving rise to a new strain of bacteria.

Question 12

how does antibiotic resistance happen so quicklY?

Answer 12

the short generation time of bacteria mean there are more opportunities for mutations to be passed on

Question 13

how are t-cells activated?

Answer 13

they have receptor proteins on their surface that bond to complementary antigens presented to them by phagocytes

Question 14

what do helper T cells do?

Answer 14

release chemical signals that activate and stimulate phagocytes and cytotoxic T cells, which kill abnormal and foreign cells.
they also activate B cells, which secrete antibodies.

Question 15

name 3 types of white blood cells

Answer 15

phagocytes
T cells
B cells

Question 16

what are B cells covered with?

Answer 16

antibodies - proteins that bind antigens to form an antigen-antibody complex

Question 17

why do different B cells bind to different shaped antigens?

Answer 17

each B cell has a different shaped antibody on its membrane.

Question 18

how do B cells work?

Answer 18

1) when the antibody on the surface of a B cell meets a complementary shaped antigen, it binds to it.
2) this, together with substances released form helped T cells, activates the B cell. this process is called clonal selection.
3) the activated B cell divides into plasma cells.

Question 19

what do plasma cells do?

Answer 19

secrete monoclonal antibodies

Question 20

what are monoclonal antibodies?

Answer 20

antibodies specific to the antigen

Question 21

what do monoclonal antibodies do?

Answer 21

bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes.

Question 22

how many binding sites does an antibody have?

Answer 22

2

Question 23

why can agglutination occur?

Answer 23

an antibody can bind to two pathogens at the same time as it has two binding sites.

Question 24

what is agglutination?

Answer 24

when pathogens become clumped together

Question 25

what forms the cellular response?

Answer 25

the T cells and other immune system cells that they interact with, e.g phagocytes

Question 26

what forms the humoral response?

Answer 26

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

Question 27

what is the primary immune response?

Answer 27

when an antigen enters the body for the first time and activates the immune system

Question 28

why is the primary immune response slow?

Answer 28

there aren’t many B cells that can make the antibody needed to bind to it

Question 29

what happens while the body is producing enough of the right antibodies to overcome an infection?

Answer 29

the infected person will show symptoms of the disease

Question 30

what happens after being exposed to an antigen?

Answer 30

t and B cells produce memory cells, which remain in the body for a long time.

Question 31

what do memory T cells do?

Answer 31

remember the specific antigen and will recognise it a second time around

Question 32

what do memory B cells do?

Answer 32

record the specific antibodies needed to bind to the antigen

Question 33

what is being immune?

Answer 33

when a persons immune system has the ability to respond to a second infection

Question 34

what is the secondary response?

Answer 34

the quicker, stronger immune response produced by the immune system if the same pathogen enters the body for the second time

Question 35

what happens during the second immune response?

Answer 35

clonal selection happens faster
memory B cells are activated and divide into plasma cells that produce the right antibody to the antigen.
memory T cells are activated and divide into the correct type of T cells to kill the cell carrying the antigen.

Question 36

what is active immunity?

Answer 36

the type of immunity you get when your immune system makes own antibodies being stimulated antigen

Question 37

name the two types of active immunity

Answer 37

natural

artificial

Question 38

what is natural active immunity?

Answer 38

when you immune after catching a disease

Question 39

what is artificial active immunity?

Answer 39

when you become immune after you’ve been given a vaccination containing a harmless dose of antigen

Question 40

what is passive immunity

Answer 40

the type of immunity you get from being given antibodies made by a different organism - your immune system doesn’t produce any antibodies of their own

Question 41

what is natural passive immunity?

Answer 41

when a baby becomes immune due to the antibodies it receives from its morgen through the placenta and in breast milk

Question 42

what is artificial passive immunity?

Answer 42

when you become immune after being injected with antibodies from someone else.
e.g if you contract tetanus you can be injected with antibodies against the tetanus toxin, collected from blood donations.