B3 - Infection and Response

What are the 4 types of pathogen?

bacteria, virus, protist, fungi

What are bacteria?

very small cells 100x smaller than body cells that rapidly reproduce

How does bacteria make you feel ill?

produce toxins that damage cells and tissues

Eg: bacterial infections

salmonella, gonorrhea

How is salmonella spread?

contaminated food

What are the symptoms of salmonella?

* fever
* vomiting
* diarrhoea

How is the spread of salmonella prevented?

* food hygiene standards
* vaccination of poultry

How is gonorrhea spread?

sexual contact

What are the symptoms of gonorrhea?

* pain when urinating
* thick yellow/green discharge from penis/vagina

How is gonorrhea treated?

antibiotics (e.g penicillin)

What is the problem with antibiotics?

some strains mutate and become resistant (e.g MRSA)

How is antibiotic resistance prevented?

not over subscribing antibiotics

How is gonorrhea prevented?

barrier methods of contraception

What is a virus?

a tiny infectious agent that use cells to replicate themselves

How does a virus make you feel ill?

cells containing reproducing viruses eventually burst, cell damage make you feel ill

Eg: viruses

measles, HIV, TMV

How is measles spread?

airborne droplets

What are the symptoms of measles?

red rash, fever

What are possible complications of measles?

pneumonia, encephalitis

How is measles prevented?

vaccination of children

How is HIV spread?

sexual contact

What are symptoms of HIV?

flu-like symptoms

How is HIV treated?

antiretroviral drugs

How does HIV make you feel ill?

attacks immune cells

What happens if HIV remains untreated?

* AIDS
* more susceptible to other disease

What is TMV?

Tobacco Mosaic Virus

What are the symptoms of TMV?

discoloured patches on leaves in mosaic pattern

How does TMV damage a plant?

decreases rate of photosynthesis → less growth

What is a protist?

all eukaryote, most single celled, some parasites

How do protists make you feel ill?

often carried by a vector and then live on/in other organisms causing damage

Def: vector

an organism that carries a protist without getting the disease itself

Eg: protist

Malaria

How is malaria spread?

* part of malarial protists’ life cycle is inside a mosquito
* mosquito pick them up and become vectors when feeding on an infected animal
* mosquito spread the protist when feeding on other animals

What are the symptoms for malaria?

repeating fever

How is malaria prevented?

* preventing mosquitos’ reproduction
* insecticides
* nets

What is fungi?

some single celled, some made up of hyphae

Def: hyphae

thread like structures

How does fungi make you feel ill?

spread by spores, penetrate human skin/plant surfaces causing disease

Eg: Fungal disease

rose black spot

What are the symptoms of rose black spot?

black/purple spots

How is rose black spot spread?

spore carried by water or wind

How does rose black spot damage rose plants?

decreases rate of photosynthesis → less growth

How is rose black spot treated?

* removal of infected leaves
* fungicides

How can pathogens be spread?

* contaminated water
* airborne droplets
* direct contact

How does the body prevent pathogens entering the body?

* skin
* tears
* mucus
* hair
* stomach acid = HCl

How do white blood cells attack pathogens?

* phagocytosis
* producing antibodies
* producing antitoxins

How does vaccination work?

* dead/inactive pathogens injected carrying antigens that cause body to produce antibodies to attack them
* when body encounters the same active pathogens, antibodies produced much quicker

What are the pros of vaccination?

control lots of communicable diseases → prevents epidemics

What are the cons of vaccination?

* don’t always work
* side effects

What drugs have come from plants?

* aspirin - willow
* digitalis - foxglove

How was penicillin discovered?

Alexander Fleming discovered area around mould on petri dishes did not grow bacteria due to production of a substance - penicillin

What are the 3 stages of drug testing?

* cells/tissues
* live animals
* clinical trials

Def: double blind trial

neither patient nor doctor know whether they are given the placebo

Def: monoclonal antibodies

copies of antibodies that target a specific antigen

How are monoclonal antibodies cloned on a larger scale?

fused with a tumour cell to divide rapidly

Why are monoclonal antibodies useful?

bind to a specific molecule

How are monoclonal antibodies used?

* pregnancy tests
* treat disease
* to find specific substances

How does a pregnancy test work?

urine containing HCG binds to pigment molecules that then bind with the results line to form positive line, if HCG not present, no line forms

How are monoclonal antibodies used to treat disease?

monoclonal antibodies can help deliver drugs to a specific part of the body e.g cancer cells by recognising its antigens

How can monoclonal antibodies help identify certain substances?

can bind with a dye to indicate presence of a substance

What is the problem with the use of monoclonal antibodies?

side effects e.g fever, low blood pressure

What physical defences do plants have?

* waxy cuticle
* cell walls
* outer layer of dead cells

What chemical defences do plants have?

* antibacterial chemicals (e.g mint)
* produce toxins (e.g deadly nightshade)

What mechanical defences do plants have?

* thorns
* hairs
* droop/curl when insect lands
* mimic other organisms