Communicable diseases

what are the 4 pathogens

bacteria

virus

fungi

protoctista

suggest how the immune system causes damage to the nervous system in autoimmune diseases (2)

1. immune system recognises antigens on neurones as foreign

2. 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)

1. callose deposited between cell wall and cell membrane of cells adjacent to infected cell to create a thick barrier for pathogen to penetrate through
2. blocks sieve plate of phloem to seal off infected area
3. 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

1. breakdown cell membranes

2. inactivate enzymes

3. 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

1. phagocyte detects antigens on pathogen
2. engulfs pathogen and encloses it in a vacuole to form a phagosome
3. lysosomes move and fuse with the phagosome to form a phagolysosome
4. enzymes from lysosome digest and destroy the pathogens

what are the main stages of phagocytosis in macrophages

1. phagocyte detects antigens on pathogen

2. engulfs pathogen and encloses it in a vacuole to form a phagosome

3. lysosomes move and fuse with the phagosome to form a phagolysosome

4. enzymes from lysosome digest and destroy the pathogens

5. antigen from pathogen is combined with glycoprotein MHC in the cytoplasm

6. MHC/antigen complex is displayed on the macrophages’ cell membrane

7. 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

1. thromboplastin released by platelets

2. thromboplastin and Ca2+ ions convert the precursor prothrombin into thrombin

3. thrombin acts as an enzyme and converts fibronigen into fibrin

4. 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

1. agglutination - act as agglutanins to clump together pathogens to make it easier to be engulfed by one phagocyte
2. opsonisation - act as opsonins to make it easier for the phagocytes to detect and engulf the pathogens
3. neutralisation - inihibits ability of pathogens to invade host cells
4. detoxification - bind to toxins produced by pathogens to make them harmless

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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

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1. T helper cells
2. T regulator cells
3. T killer cells
4. T memory cells

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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

1. plasma cells
2. 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)

1. Pathogen is made safe and injected

2. antigen presentation/T helper cells bind to antigen

3. clonal selection, clonal expansion, and antibodies produced

4. 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

1. due to a random mutation, a small population of the bacteria are not affected by the antibiotic
2. the other bacteria are killed so there is less competition
3. the resistant bacteria are more likely to survive and reproduce
4. bacteria reproduce rapidly and all their daughters are resistant as well
5. 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)