immunity

Question 1

primary defences

Answer 1

• skin
• lysozymes
• mucous membranes
• stomach acid
• nasal airs/ ear wax

Question 2

where are lysozymes found

Answer 2

tears

Question 3

what do mast cells do

Answer 3

• release histamines and cyokines

Question 4

what do histamines do

Answer 4

• make blood vessels dilate, causing localised heat and redness.
• increase permeability of blood vessels which means more blood plasma is forced out - tissue fluid which causes swelling and pain

Question 5

what do cytokines do

Answer 5

stimulate specific immune response
stimulate phagocytes to move to site of infection/inflammation
increase body temp

Question 6

what causes blood clotting

Answer 6

platelets which are cell fragments that have broken off from other larger cells
they prevent pathogens/parasites from entering the blood stream

Question 7

what is core body temperature controlled by

Answer 7

hypothalamus

Question 8

what is a fever

Answer 8

infection causes cytokines to stimulate the hypothalamus to reset to a higher temp
because pathogens cannot reproduce as quickly at temperature above 37 degrees, and the specific immune sytem can work faster

Question 9

what is a neutrophil

(70% of white blood cells are neutrophils)

Answer 9

• made in bone marrow
• multilobed nucleus
• released in large numbers during an infection
• rapid action
• short lived - often die after taking in and destroying bacteria
• travel in blood and often squeeze out of blood into tissue fluid

Question 10

what are macrophages

make up 4% of white blood cells

Answer 10

• made in the bone marrow; found in large quantities in the lymphnodes
• have a C-shaped nucleus
• slightly slower action
• play an important role in initiating the specific response
• larger
• travel in blood as monocytes

Question 11

how are phagocytes able to pass from the blood into the tissue fluid

Answer 11

• they have a lobed/narrow nucleus
• they can change shape
• can squeeze/fit between cells in walls of capillaries

Question 12

what do opsonins do

Answer 12

• enhances phagocytosis by marking an antigen for an immune response

(latin for get ready to eat)

Question 13

phagocytosis process

Answer 13

1. a phagocyte recognises the antigens on a pathogen
2. the membrane and cytoplasm of the phagocyte move round the pathogen, engulfing it (endocytosis)
3. the pathogen is not contained in a phagosome (phagocytic vacuole) in the cytoplasm of the phagocyte
4. a lysosome fuses with the phagosome (to form a phagolysosome).
5. digestive enzymes from the lysosome break down the pathogen

Question 14

what are T lymphocytes activated by

Answer 14

phagocytes

Question 15

features of a T lymphocyte

Answer 15

• another type of white blood cell
• their surface is covered in receptors
• the receptors bind to antigens presented by antigen presenting cells
• when the receptor on the surface of a T cell meets a complementary antigen - it binds
• this activates clonal expansion

Question 16

what is clonal expansion

Answer 16

when a T/B lymphocyte divides to produce clones of itself - different clones carry out different functions

Question 17

different types of T lymphocytes

Answer 17

T helper cells - these release interleukins to activate B lymphocytes and T killer cells
T killer cells - attach to and kill cells that are infected with a virus
memory cells - remain in your blood and recognise the specific antigen quickly a second time around, should you be infected with the same pathogen

Question 18

B lymphocyte features

Answer 18

• type of white blood cell
• they’re covered with antibodies - proteins which bind antigens to form an antigen-antibody complex
• each B-lymphocyte has a different shaped antibody on its membrane so different ones bind to different shaped antigens

Question 19

what do B lymphocytes divide into

Answer 19

plasma cells
memory cells - detect antigen at a later date and then develop into plasma cells

Question 20

what do B-plasma cells do

Answer 20

secrete loads of the antibody specific to the antigen into the blood
these antibodies will bind to the antigens on the surface of the pathogen to form many complexes
–> this is the signal for the immune system to attack and destroy the pathogen

Question 21

what is cell signalling + how does it happen

Answer 21

cell signalling is how cells communicate.
a cell may release a substance that binds to the receptors on another cell causing a response
imporant in the immune system because it helps activate all the different types of white blood cells that are needed

Question 22

antibody structure

Answer 22

glycoproteins
4 polypeptide chains - two heavy and two light
each chain has a variable region and a constant regiong

Question 23

what are the variable regions of an antibody

Answer 23

form the antigen binding sites
the shape of the variable region is complementary to a particular antigen
variable regions differ between antibodies

Question 24

what is the hinge region of an antibody

Answer 24

allows flexibility when the antibody binds to the antigen

Question 25

what is the constant region of an antibody

Answer 25

allow binding to receptors on immune sytem cells e.g. phagocytes. the constant region is the same (same sequence of amino acids) in all antibodies

Question 26

what bond holds polypeptide chains together in an antibody

Answer 26

disulfide

Question 27

how to antibodies clear an infection | state 3 ways

Answer 27

1. aggultinating pathogens 2. neutralising toxins 3. preventing the pathogen binding to human cells

Question 28

what is agglutinating

Answer 28

each antibody has two binding sites, so an antibody can bind to two pathogens at one - pathogens become clumped together phagocytes then bind to the antibody and phagocytose a lot of pathogens at once

Question 29

how do antibodies neutralise toxins

Answer 29

antibodies called anti-toxins can bind to the toxins produced by pathogens this prevents the toxins from affecting human cells so toxins are neutralised (inactivated) the toxin-antibody complexes are phagocytosed

Question 30

how do antibodies prevent the pathogen binding to human cells

Answer 30

when antibodies bind to the antigens on pathogens, they may block the cell surface receptors that the pathogens need to bind to the host cells this means the pathogen can't attach or infect the host cells

Question 31

active immunity meaning

Answer 31

when your immune sytem makes it own antibodies after being stimulated by an antigen

Question 32

natural active immunity

Answer 32

when you become immune after catching a disease e.g having measles as a child, you shouldn't be able to catch it again in later life

Question 33

artificial active immunity

Answer 33

you become immune after you've been given a vaccination containing a harmless dose of an antigen

Question 34

passive immunity

Answer 34

type of immunity you get from being given antibodies made by a different organism - your immune systm doesn't produce any antibodies of its own

Question 35

natural passive

Answer 35

when a baby becomes immune due to antibodies it recieves from its mother, through placenta and in breast milk

Question 36

artificial active

Answer 36

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

Question 37

what is autoimmune disease

Answer 37

- an organisms immune system isn't able to recognise self-antigens (antigens present on the organisms own cells). - when this happens the immune system treats the self-antigens as foreign antigens and launches an immune response against the organisms own tissues

Question 38

what is a vaccine

Answer 38

contain substances that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease meaning you become immune without getting any symptoms subtances may be antigens which could be free or attached to a dead or weakened pathogen

Question 39

disadvantage of taking vaccines orally

Answer 39

it could be broken down by enzumes in the gut or molecules of the vaccine may be too large to be absorbed into the blood

Question 40

what is herd immunity

Answer 40

epidemics can be prevented if a large percentage of the population are vaccinated. --> even people who haven't been vaccinated are unlikely to get the disease because there's no one to catch it from