Studied by 16 peoplewhat are the 4 pathogens
bacteria
virus
fungi
protoctista
suggest how the immune system causes damage to the nervous system in autoimmune diseases (2)
immune system recognises antigens on neurones as foreign
produces antibodies against the neurones
OR phagocytes break down the neurones
what is a vector
something that spreads pathogens between organisms
what is the structure of a virus
DNA or RNA contained in protein structure called capsid.
Attachment proteins on surface to attach to host cells
how do plants recognise an attack (4)
receptors respond to molecules from pathogen (1)
or to breakdown products when cell wall is attacked (1)
stimulates release of signal molecules (1)
signal molecules turn on certain genes to trigger response (1)
3 plant responses to infection
synthesis of callose and lignin
synthesis of defensive chemicals to alert nearby cells
synthesis of defensive chemicals to attack the pathogen
structure of callose
beta glucose
1-3 and 1-6 glycosidic bonds
how do plants limit the spread of pathogens using callose (3)
callose deposited between cell wall and cell membrane of cells adjacent to infected cell to create a thick barrier for pathogen to penetrate through
blocks sieve plate of phloem to seal off infected area
blocks plasmodesmata between infected and nearby cells
what is the role of lignin in preventing spread of pathogens in plants
reinforces callose walls to create a thicker barrier
how do viruses infect an organism
attach to cell using attachment proteins
inserts genetic material into DNA of host cell
viral genetic material is replicated
new viruses burst out of host cell and kill the host
methods of physical defence in plants
waxy cuticle
bark
cell wall
stomatal closure
how to plants and animals differ against pathogens
animals heal tissue but plants seal off and sacrifice tissue
function of tylose in limiting pathogen spread in plants
blocks xylem vessels
what are the different chemicals plants can produce to defend against pathogens
insect repellants
insecticides
antibacterial compounds
antifungal compounds
anti-oomycetes
general toxins
how do bacteria infect an organism (2)
produce toxins
which poison or damage host cells
what are the 3 ways in which toxins can affect an organism
breakdown cell membranes
inactivate enzymes
interfere with genetic material so host cells cannot divide
how do protists infect an organism
digest cell and cell contents as they reproduce
how do fungi infect an organism
digest and destroy living cells by releasing extracellular enzymes from their hyphae
examples of disease caused by bacteria
tuberculosis
bacterial meningitis
ring rot (potatoes and tomatoes)
examples of disease caused by viruses
HIV/AIDS
influenza
tobacco mosaic virus
examples of disease caused by protists
malaria
potato/tomato late blight
examples of disease caused by fungi
black sigatoka (bananas)
ringworm (cattle)
athlete’s foot (humans)
what is direct transmission of pathogen
pathogen is transmitted directly from one organism to another
what is indirect transmission
pathogen is transmitted from one organism to another through another medium
what are the methods of direct transmission of pathogens in animals
contact of body fluids
skin to skin contact
through breaks in skin
from animal bite
sharing needles
taking in contaminated food and drink
what are the methods of indirect transmission of pathogens in animals
fomites
droplets in air
vectors
what is a fomite
inanimate object which can carry pathogens
e.g. clothes, bedding
factors affecting transmission of disease in animals
overcrowding
poor nutrition
compromised immune system
poor healthcare and infrastructure
climate change
culture
what are the methods of direct transmission of pathogens in plants
direct contact between infected and healthy plant
what are the methods of indirect transmission of pathogens in plants
soil contamination
vectors
examples of vectors that transmit plant disease
wind (spread fungal and oomycete spores)
water
animals
humans
factors affecting transmission of disease in plants
overcrowding
poor nutrition
climate change
planting succeptible plants
damp warm conditions is favourable for pathogens
methods of reducing spread of communicable disease in plants
clear fields after infected crops
rotate crops
strict hygiene practises
control insect vectors
plant variety of susceptible plants
what are the non specific defences of the human body (8)
skin
mucous membraines
blood clotting
wound repair
phagocytosis
inflammation
expulsive reflexes
acid in stomach
how does the skin act as a non-specific defence against pathogens
prevents entry of pathogens into the body
secretes sebum (oily substance) to inhibit growth of pathogens
how do mucous membranes act as non-specific defence against pathogens
produce mucus which trap pathogens
contain lysosomes and phagocytes to destroy pathogens
how do expulsive reflexes act as non-specific defence against pathogens
coughing and sneezing removes mucus with pathogens from airways
vomiting and diorrhoea remove any pathogens in the gut
what is the function of thromboplastin in wound repair
an enzyme which triggers the coagulation cascade to form a blood clot
what is the function of seretonin in wound repair
contracts smooth vessel in walls of blood vessel near the wound to restrict blood loss at the wound
what are the signs of inflammation
redness
heat
swelling
pain
which chemicals are released by the mast cells in the inflammatory response
histamines and cytokines
what is the function of histamines in the inflammatory response (4)
vasodilation to cause redness and localised heat to kill pathogens
make walls of blood vessels more leaky so more tissue fluid forms to cause swelling and pain
what is the function of edema (2)
provide nutrients and immune cells to site of infection
helpts to dilute and remove pathogens from the area
what is the function of cytokines in the non specific immune response (4)
act as signalling molecules to attract phagocytes to site of infection
regulate the intensity and duration of the inflammatory response
increase body temperature
stimulate specific immune system
what are the 2 types of phagocytes involved in the non specific immune response
neutrophils and macrophages
differences in structure between neutrophils and macrophages
neutrophil has lobed nucleus to squeeze through narrow gaps - macrophage has round nucleus as it stays in blood
what is the contents of pus
dead neutrophils and pathogens
what are the main stages of phagocytosis of neutrophils
phagocyte detects antigens on pathogen
engulfs pathogen and encloses it in a vacuole to form a phagosome
lysosomes move and fuse with the phagosome to form a phagolysosome
enzymes from lysosome digest and destroy the pathogens
what are the main stages of phagocytosis in macrophages
phagocyte detects antigens on pathogen
engulfs pathogen and encloses it in a vacuole to form a phagosome
lysosomes move and fuse with the phagosome to form a phagolysosome
enzymes from lysosome digest and destroy the pathogens
antigen from pathogen is combined with glycoprotein MHC in the cytoplasm
MHC/antigen complex is displayed on the macrophages’ cell membrane
macrophage becomes an antigen presenting cell to stimulate other phagocytes
what is the full form of the glycoprotein MHC
major histocompatibilty complex
what is the function of opsonins in the non specific immune system (3)
non-specific proteins which bind to antigens on pathogen
tag them so they are more easily recognised by phagocytes
phagocytes have receptors to bind to common opsonins
which cells trigger the inflammatory response
mast cells
main steps of the coagulation cascade
thromboplastin released by platelets
thromboplastin and Ca2+ ions convert the precursor prothrombin into thrombin
thrombin acts as an enzyme and converts fibronigen into fibrin
fibrin forms a mesh which traps red blood cells forming the clot
where are neutrophils found
blood
tissue fluid
epithelial surfaces
when does a pathogen kill a person
if the pathogen is aggressive enough and replicates enough before clonal selection is completed
what causes fevers
cytokines signal to hypothallamus to raise body temperature
what is the benefit of fever
higher temperatures inhibits growth of pathogens
specific immune system works faster at higher temperatures
how does the body detect a pathogen cell
detects antigen on pathogen cell as non-self
which immune system takes longer to be triggered when a pathogen infects for the first time
the specific immune system takes longer
what is another name for antibodies
immunoglobulin
what type of proteins are antibodies/immunoglobulins
quaternary glycoproteins
what is the structure of antibodies
2 heavy chains and 2 light chains held together by disulfide bridges
binding site made of different amino acids called the variable region
constant region where white blood cells bind to antibody
hinge region for flexiblity
what makes antibodies specific
the variable region on each antibody is made of different sequence amino acids so different shapes to bind to different antigens
how many antigens can 1 antibody bind to
2
what are the functions of antibodies
agglutination - act as agglutanins to clump together pathogens to make it easier to be engulfed by one phagocyte
opsonisation - act as opsonins to make it easier for the phagocytes to detect and engulf the pathogens
neutralisation - inihibits ability of pathogens to invade host cells
detoxification - bind to toxins produced by pathogens to make them harmless
what is the name of the structure formed when an antibody binds to an antigen
antigen-antibody complex
where do all lymphocytes originate from
bone marrow
where do b-lymphocytes mature
bone marrow
where do t-lymphocytes mature
thymus gland
what are the different types of t-lymphocytes
T helper cells
T regulator cells
T killer cells
T memory cells
what is the overall function of B cells
produce antibodies for a specific antigen to kill pathogens by phagocytosis
what is the overall function of T cells
kill infected cells
stimulate B cells to produce more antibodies
what is the function of T helper cells
has CD4 receptors on cell surface membranes
binds to complimentary antigen on antigen presenting cell
releases interleukins
activate B cells, T killer cells, stimulate macrophages
what is the function of T killer cells
kill pathogens with specific antigens
kill any infected cells
how do T killer cells kill
produce chemical perforin
makes holes in the cell membrane of the pathogen
what is the function of T regulator cells
regulate the immune system
stop the immune response once the pathogen is dealt with
prevent autoimmune diseases
what is the function of T memory cells
immunological memory
rapidly divide when a known pathogen’s antigen is detected
form clones of T killer cells
what are the types of B-lymphocytes
plasma cells
B memory cells
what is the function of plasma cells
produce antibodies for a particular antigen after clonal selection
what is the function of B memory cells
immunological memory
remember specific antigen
trigger secondary immune response rapidly if antigen is encountered again
what is the function of cell mediated immunity
to kill infected cells
what occurs in cell mediated immunity
correct T helper cell binds to antigen on APC (clonal selection)
T helper cells divide and stimulate: (clonal expansion)
production of T memory cells
production of T killer cells
production of interleukins to stimulate B cells to divide
what is the function of humoral immunity
to deal with pathogens in the blood which have not infected cells yet
what occurs in humoral immunity
B cell with complimentary receptor binds antigen on pathogen (clonal selection)
B cells divide rapidly (clonal expansion)
Differentiate into plasma cells and memory cells
Plasma cells release antibodies specific to that antigen into the blood
why is the primary immune response slower than the secondary immune system
in the primary response clonal selection needs to take place which takes a long time
in secondary immune system no clonal selection is needed as the memory cells initiate clonal expansion rapidly as soon as the pathogen is detected
what are 3 examples of autoimmune diseases
rheumatoid arthritis
lupus
type 1 diabetes
what is an autoimmune disease
abnormal immune response against tissues normally in the body
what is the treatment for autoimmune diseases
immunosupressants
what is natural active immunity
when the body makes antibodies to a pathogen on its own
what is natural passive immunity
when a fetus gets antibodies from the breast milk of the mother
what is artificial active immunity
when the immune system is stimulated to make antibodies by injecting it with a dead/inactive pathogen - vaccinesw
what is artificial passive immunity
when antibodies for a pathogen are injected into the body - gives temporary immunity
what are the steps of vaccination (4)
Pathogen is made safe and injected
antigen presentation/T helper cells bind to antigen
clonal selection, clonal expansion, and antibodies produced
memory cells produced for immunological memory
what are the possible sources of medicine
plants, mould, fungi, venom of animals
what is the term given to the mode of action of antibiotics
selective toxicity
how do antibiotic resistant bacteria strains develop
due to a random mutation, a small population of the bacteria are not affected by the antibiotic
the other bacteria are killed so there is less competition
the resistant bacteria are more likely to survive and reproduce
bacteria reproduce rapidly and all their daughters are resistant as well
soon majority of the bacteria population will be resistant
name of pathogen which carries malaria
plasmodium
Explain why the response to the subsequent infection is much bigger than the response to vaccination (3 marks)
explain why vaccinations are an example of active immunity (2 marks)
Note 
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