Communicable diseases

bacteria

virus

fungi

protoctista

1. immune system recognises antigens on neurones as foreign

2. produces antibodies against the neurones

   OR phagocytes break down the neurones

something that spreads pathogens between organisms

DNA or RNA contained in protein structure called capsid.

Attachment proteins on surface to attach to host cells

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)

synthesis of callose and lignin

synthesis of defensive chemicals to alert nearby cells

synthesis of defensive chemicals to attack the pathogen

beta glucose

1-3 and 1-6 glycosidic bonds

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

reinforces callose walls to create a thicker barrier

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

waxy cuticle

bark

cell wall

stomatal closure

animals heal tissue but plants seal off and sacrifice tissue

blocks xylem vessels

insect repellants

insecticides

antibacterial compounds

antifungal compounds

anti-oomycetes

general toxins

produce toxins

which poison or damage host cells

1. breakdown cell membranes

2. inactivate enzymes

3. interfere with genetic material so host cells cannot divide

digest cell and cell contents as they reproduce

digest and destroy living cells by releasing extracellular enzymes from their hyphae

tuberculosis

bacterial meningitis

ring rot (potatoes and tomatoes)

HIV/AIDS

influenza

tobacco mosaic virus

malaria

potato/tomato late blight

black sigatoka (bananas)

ringworm (cattle)

athlete’s foot (humans)

pathogen is transmitted directly from one organism to another

pathogen is transmitted from one organism to another through another medium

contact of body fluids

skin to skin contact

through breaks in skin

from animal bite

sharing needles

taking in contaminated food and drink

fomites

droplets in air

vectors

inanimate object which can carry pathogens

e.g. clothes, bedding

overcrowding

poor nutrition

compromised immune system

poor healthcare and infrastructure

climate change

culture

direct contact between infected and healthy plant

soil contamination

vectors

wind (spread fungal and oomycete spores)

water

animals

humans

overcrowding

poor nutrition

climate change

planting succeptible plants

damp warm conditions is favourable for pathogens

clear fields after infected crops

rotate crops

strict hygiene practises

control insect vectors

plant variety of susceptible plants

skin

mucous membraines

blood clotting

wound repair

phagocytosis

inflammation

expulsive reflexes

acid in stomach

prevents entry of pathogens into the body

secretes sebum (oily substance) to inhibit growth of pathogens

produce mucus which trap pathogens

contain lysosomes and phagocytes to destroy pathogens

coughing and sneezing removes mucus with pathogens from airways

vomiting and diorrhoea remove any pathogens in the gut

an enzyme which triggers the coagulation cascade to form a blood clot

contracts smooth vessel in walls of blood vessel near the wound to restrict blood loss at the wound

redness

heat

swelling

pain

histamines and cytokines

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

provide nutrients and immune cells to site of infection

helpts to dilute and remove pathogens from the area

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

neutrophils and macrophages

neutrophil has lobed nucleus to squeeze through narrow gaps - macrophage has round nucleus as it stays in blood

dead neutrophils and pathogens

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

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

major histocompatibilty complex

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

mast cells

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

blood

tissue fluid

epithelial surfaces

if the pathogen is aggressive enough and replicates enough before clonal selection is completed

cytokines stimulate hypothallamus to raise body temperature

higher temperatures inhibits growth of pathogens

specific immune system works faster at higher temperatures

detects antigen on pathogen cell as non-self

the specific immune system takes longer

immunoglobulin

quaternary glycoproteins

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

the variable region on each antibody is made of different sequence amino acids so different shapes to bind to different antigens

2

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

antigen-antibody complex

bone marrow

bone marrow

thymus gland

1. T helper cells

2. T regulator cells

3. T killer cells

4. T memory cells

produce antibodies for a specific antigen to kill pathogens by phagocytosis

kill infected cells

stimulate B cells to produce more antibodies

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

kill pathogens with specific antigens

kill any infected cells

produce chemical perforin

makes holes in the cell membrane of the pathogen

regulate the immune system

stop the immune response once the pathogen is dealt with

prevent autoimmune diseases

immunological memory

rapidly divide when a known pathogen’s antigen is detected

form clones of T killer cells

1. plasma cells

2. B memory cells

produce antibodies for a particular antigen after clonal selection

immunological memory

remember specific antigen

trigger secondary immune response rapidly if antigen is encountered again

to kill infected cells

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

to deal with pathogens in the blood which have not infected cells yet

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

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

rheumatoid arthritis

lupus

type 1 diabetes

abnormal immune response against tissues normally in the body

immunosupressants

when the body makes antibodies to a pathogen on its own

when a fetus gets antibodies from the breast milk of the mother

when the immune system is stimulated to make antibodies by injecting it with a dead/inactive pathogen - vaccinesw

when antibodies for a pathogen are injected into the body - gives temporary immunity

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

plants, mould, fungi, venom of animals

selective toxicity

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

plasmodium