Biology topic 3

what are microorganisms

a group of tiny organisms including bacteria, viruses, protists and fungi.

do organisms cause problems

organisms don’t cause problems but a small group of them do and are called pathogens

what is a pathogen

microorganisms that enter the body and cause diseases. they cause communicable (infectious) diseases - diseases that can spread.

what are bacteria

• type of organism

• size

• what they do

• how they make you ill

single celled organisms

very small (1/100th) of body cells

they reproduce rapidly because of good food supply

make you feel ill by producing toxins (poisons) that can damage your cells and tissues

what are viruses

• type of cells

• size

• what they do

• how they make you feel ill

they are not cells and not living

they are tiny (1/100th of bacteria)

they reproduce rapidly inside your body

they live inside your cells and replicate themselves using cell machinery. the cell usually bursts releasing all new viruses that find new cells to take over. the cell damage is what makes you feel ill.

what are protists

• type of cell

• what parasites do

• what parasites are transferred by

all eukaryotes and most are single-celled

some protists are parasites

parisites live on or inside other organisms and cause them damage.

often transferred to the organism by a vector - which doesn’t get the disease itself

what is fungi

• type of cell

• what hyphae can do

some fungi are single celled others have body made up of hyphae (thread like structure)

hyphae grow and penetrare human skin and the surface of plants causing disease

hyphae produce spores which can be spread to other plants/animals

how can pathogens be spread - 3 ways

water/food - some pathogens can be picked up by drinking or bathing in dirty water

air - pathogens can be carried in the air and then breathed in

direct contact - some pathogens can be picked up by touching contaminated surfaces including skin

measles

• what type of disease is it

• how it is spread

• symptoms

• how you can be protected

spread by droplets when infected person coughs / sneezes

causes red rash across body, fever

can be serious/ fatal but rare

people vaccinated against it when young

HIV

• what type of disease is it

• how it is spread

• what it does

• symptoms

Human Immunodeficiency Virus

spread by sexual contact or y exchanging bodily fluids like blood

can happen when people share needles when taking drugs

infects and destroys cells that normally help to defend the body against disease - makes people with HIV more likely to get ill from infection by other pathogens

initially causes flu like symptoms

HIV - what happens if they are not treated against it

after initial flu like symptoms, the person doesn’t experience any symptoms for several years

throughout that time the virus is doing more damage to your body

immune system weakens and you start to catch unusual invection and could develop cancers

if immune system is badly damaged, it can’t cope with any other infections or cancers

now the virus is known as late stage HIV infection or AID’s

how can HIV be controlled

by antiretroviral drugs

these stop the virus replicating in the body

tobacco mosaic virus (TMV)

• what it affects

• what it causes

• symptoms

affects many species of plants (e.g. tobacco or tomato)

causes mosaic pattern on leaves of plants

parts of oeaves become discoloured

discolouration means plant can’t carry out photosynthesis affecting growth

hyphae

• what are they

• how they are spread

• what they do to skin

• what they produce

multi - cellular have long thread like structures

spread through the plants

penetrate skin (causes disease)

produces spores which spread and grow into new fungi

what are fungal disease

eukaryotic organisms - can be uni or multi-cellular

rose black spot

• type of disease

• what it causes

• how the leaves react

• how it spreads

causes purple or black spots to develop on the leaves of rose plants

leaves turn yellow and drop off

less photosynthesis can happen so the plant does not grow well

spreads in water or by wind

how can you treat rose black spots

use fungicides and strip the plant of affected leaves

leaves need to be destroyed so the fungus can’t spread to other rose plants

what is malaria

• cause

• transported how and by what

caused by parisitic protists - needs a host to survive

transported by mosquitoes

they suck up parasites hwen they feed on an infected animal

every time the mosquito feeds on another animal it infects it by inserting the protist in the animal blood vessel and protist spreads to new host

malaria

• symptoms

• how spread of malaria can be reduced

causes repeating episodes of fever

can be fatal

destroy breeding sites (they can breed in water so get rid of water source)

killing with insecticides

mosquito nets

mosquito repellent

salmonella food poisoning - bacterial disease

• how it can be caught

• symptoms & how they are cause

• example

caught by any food contaminated with the bacteria

people can suffer from fever, stomach cramps, vomiting, diarrhoea

symptoms caused by the toxins that the bacteria produce

passes by itself in a week

e.g. eating chicken that caught the disease when alive, eating food that has been contaminated by being prepared in hygienic conditions

gonorrhoea

• what it is

• how it is passed on

• symptoms

• avoid how

sexually transmitted disease (STD)

STD’s passed on by sexual contact e.g. unprotected sex

pain when urinating, thick yellow or green discharge from vagina or penis

avoid unsafe sex, use barrier methods of contraception (condoms)

gonorrhoea treatment and why it is not so good

penicillin - gonorrhoea strains (different types) become resistant to penicillin

rarer and more expensive antibiotics have been needed

people can be treated with other antibiotics

reducing and preventing spread of disease - 4 things

• being hygienic - washing hands or cleaning cooking items

• destroying vectors - by getting rid of these this prevents the disease from being passed on, also could use insecticides

• isolating infected individuals - prevents isolated person from passing it on

• vaccination - can’t develop the infection and then pass it on

difference between communicable and non - communicable disease

communicable disease can be spread from person-person and non-communicable can’t

features human body has stopping pathogens from entering the body - physical barriers

• skin, kills pathogens

• hair, mucus in your nose trap particles that could contain pathogens

• trachea and cronchi lined with cilia - hair like structures that waft mucus up to back of throat where it can be swallowed

features human body has stopping pathogens from entering the body - chemical barriers

• stomach produces hydrochloric acid - kills pathogens that make it that far from mouth

what does the immune system do

if pathogens make it in your body the immune system kicks in to destroy them. most important type of immune system is white blood cells. they travel around your body and crawl in every part of you patrolling microbes.

1 way the white blood cells destroy pathogens - phagocytosis

tracking pathogens

binding to them

engulf foreign cells and digesting them

1 way the white blood cells destroy pathogens - antitoxins

pathogens produce toxins that can kill cells

antitoxins produce - counteract toxins produced by the invading bacteria

1 way the white blood cells destroy pathogens - antibodies

antigens - invading (foreign) pathogens have unique molecules on its surface

when you white blood cells come across a foreign antigen, they will start to produce proteins called antibodies to lock onto invading cells so they can be found and destroyed by other white blood cells

the antibodies produced are specific to that type of antigen - won’t lock on to others

antibodies are produced rapidly and carried arounf body to find silmilar bacteria or viruses

what happens if the person is infected with the same pathogen - white blood cells

white blood cells rapidly produce antibodies to kill pathogen

the person is naturally immune to that pathogen as they have already had it and won’t get ill

what do vaccinations involve

involve injecting small amounts of weakened, dead or inactive pathogens

they carry antigens which cause your white blood cells to produce antiodies to attack them - even though the are harmless

what do vaccines work on

bacteria or viruses

what happens if pathogens of the same type appear at a later date

white blood cells can rapidly mass produce antobodies to kill off the pathogen.

the vaccinated person is now immune to that pathogen and won’t get ill

vaccination pros

• protection from diseases

• controls common diseases (polio, measles, whooping cough)

• prevent outbreak (epidemics) - kills lots of people

• herd immunity, lots of people vaccinated even if 1 person gets disease the pathogen won’t spread to others easily

vaccination cons

• don’t always work - sometimes don’t give you immunity

• sometime have reaction to vaccine (fever) but bad reactions are rae (seizures)

balancing the risks

deciding whether to have a vaccination means balancing risks - risk of catching disease if you don’t have a vaccine against the risk of having a reaction if you do.

what are painkillers and what do they do

example - aspirin

drugs that relive pain

they don’t actually tackle the cause of the disease they just help reduce the symptoms

antibiotics what they do

example - penicillin

kill (or prevent growth of) the bacteria causing the problem without killing your own body cells

different antibiotics kill different bacteria so important to be treated with right one

what do antibiotics not destroy

they don’t destroy viruses (e.g. flu or cold)

viruses reproduce using their own body cells making it difficult to develop drugs that destroy just the virus without killing the body cells

even if antibiotics could fight viruses they wouldn’t be able to find them as viruses hide within our body cells making it impossible to kill them without killing our body cells to

how can bacteria become resistant

bacteria can mutate

sometimes the mutations cause them to be resistant (not killed by) an antibiotic

if you have an infection some of the bacteria may be resistant to antibiotics

when you treat the infection only the non-resistant strains of bacteria will be killed

the individual resistant bacteria will survive and reproduce and population of resistant strain will increase. this is e.g. of natural selection

the resistant strain could cause a serious infection that can’t be treated by antibiotics

slowing down the development of antibiotic resistance

to slow down the rate of development of resistant strains it is important doctors don’t overprescribe antibiotics

it is also important you finish the whole course of antibiotics and don’t just stop when your better

what is aspirin and how was it developed

used as a painkiller and to lower fever

developed from a chemical found in willow

what is digitalis and how was it developed

used to trat heart conditions

developed from a chemical found in foxgloves

how was penicillin discorvered

alexandra Flemming returned from a lab and noticed bacteria growing in a petri dish

he found the fungus produced a substance that was able to kill the bacteria

because the gene of the fungus is penillium it is called penicillin

how do you prepare the work area for the aseptic technique (procedure carried out to prevent the contamination of pure cultures of microorganisms) petri dish prac

1. clear the work space of all non- essential items

2. clean the workspace with disinfectant

• kills all unwanted bacteria and so decreases the chance of agar plate becoming contaminated

preparing the agar plates for growth of bacteria

glass petri dish and agar gel must be sterilised before use by using an autoclave or pre sterilised plastic petri dishes can be bought

• reason - kills any unwanted bacteria that are present in the solution or on petri dishes

pour agar into sterile petri dishes and allow to set fully

• reason - provides the selected bacterium with all the nutrients needed to grow

plating the bacteria (putting bacteria on agar gel) steps

1. everything should be done beside a blue bunsen flame

• reason - stop the agar getting contaminated with unwanted bacteria from air

2. swirl the bacteria to make sure the bacteria culture is well mixed

• reason - make sure the bacteria aren’t all at the bottom of the container

3. sterilise the inoculating loop by heating it in bunsen. or sterlise by putting it in alcohol for few seconds

• reason - kills any unwanted bacteria present in the loop

4. remove lid of bacteria bottle and put mouth of bottle in bunsen flame

• kill off any unwanted bacteria that could be on bottle

5. dip inoculation loop in micro organism solution and make streaks on surface of agar plate

• reason - allows bacteria to spread out to grow in individual colonies on agar plate

6. secure the lid with tape

• reason - lid stops additional unwanted bacteria from air contaminating the plate. don’t fully seal lid as will stop oxygen reaching bacterium

7. incubate at a max temp 25 degrees

• reduces chance of growing harmful pathogen that would grow at 37 degrees in human body

clearing up petri dish practical

1. all contaminated materials disposed

2. all work surfaces disinfected and ensure hands washed with soapy water

why is drug testing done

to make sure the drugs are safe and effective

stage 1 of preclinical testing

cells and tissues

drugs tested on human cells and tissues in the lab

you can’t use them to test drugs that affect whol organs or entire organisms

cheaply test lots of substances

stage 2 preclinical testing

live animals

test of live animals to test effiancy (whether drug works and produces affect looking for) and to find out about toxicity (how harmful) and to find best dosage (concentration that should be given and how often its given)

what does the law say about stage 2 preclinical testing

law in britain states any new drug must be tested on 2 different live mammals

what do some people think about testing on animals

people think it’s cruel to test on animals, but others believe this is the safest way to make sure a drug isn’t dangerous before it's given to humans. 

Other people think that animals are so different from humans that testing on animals is pointless 

stage 3 clincal trials

tested on human volunteers

first drug tested on healthy volunteers to make sure it doesn’t have any harmful side effect when the body is working normally

very low dose of drug is given and is slowly increased to find maximum dosage without side effects

what happens if the drug is good when tested on healthy volunteers

if the results are good the drug is tested on suffering people with the illness. the optimum dose is found - dose of drug that is most effective with few side effects

what is a placebo and why is it done

patients put in 2 group

1 drug given to 1 and other given a placebo - substance like the drug but does nothing

so the doctor can see the difference the drug makes - allws for the placebo effect (patient expects teatment to work so feels better even though treatment does nothing)

why are the results of drug testing and trial not published until they have been through peer review

prevents false claims

what are blind and double blind trials

clinical trials are blind - patient in study doesn’t know whether they are getting drug/placebo

often they are double blind - niether patient nor doctor know until results gathered

this is so the doctor monitering the patients and analysing the results aren’t subconciously influenced by their knowledge / biased

why is it important drugs are tested

make sure they are safe

what can plants catch diseases from

from microorganisms (fungi, viruses, bacteria) , larger organisms (insects) or deficiency diseases 

what is a deficiency disease

Plants need mineral ions from soil.

If there aren’t enough, plants suffer deficiency symptoms

Nitrates needed to make proteins and therefore for growth. Lack of nitrates causes stunted growth

Magnesium ions needed for making chlorophyll which is needed for photosynthesis.

Plants without enough magnesium suffer from chlorosis (not enough chlorophyll made) and have yellow leaves

what are diseases caused by pathogens

Infestation with pests - Plants can also be infested and damaged by insects.

Aphids are an insect that can cause damage to plants. Infestations of pests are easy to spot - you should be able to see them on plants

signs to detect plant diseases

Stunted growth

Spots on the leaves

Patches of decay (rot)

Abnormal growths, e.g. lumps

Malformed stems or leaves

Discolouration

what is crown gall

bacterial disease that causes growths on plants 

how can you identify plant diseases

• Looking up the signs in a gardening manual or on a gardening website

• Taking the infected plant to a lab and scientists can identify the pathogen

• Using testing kits that identify the pathogen using monoclonal antibodies

what defences do plants have

Plants have physical, chemical and mechanical defences against pests and pathogens 

what are physical plant defences

waxy cuticle, which provide a barrier to stop pathogens entering

cell walls made from cellulose, these form a physical barrier against pathogens that make it past the waxy cuticle

Plants have layers of dead cells around their stems, the outer part of bark on trees. These act as barriers to stop pathogens from entering

what are chemical plant defences

• antibacterial chemicals which kill bacteria, the mint plant and witch hazel 

• poisons which can deter herbivores (organisms that eat plants) e.g. tobacco plants, foxglove and deadly nightshade

what are mechanical plant defences

• thorns and hairs, these stop animals from touching and eating them 

• leaves that droop or curl when something touches them. This means that they can prevent themselves from being eaten by knocking insects off themselves and moving away from things

• mimic other organisms, the passion flower has bright yellow spots on its leaves which look like butterfly eggs. This stops other butterflies from laying their eggs there. Several species of plant in the ‘ice plant family’ in southern Africa look like stones and pebbles. This tricks other organisms into not eating them