3- infection and response

Question 1

what is a pathogen

Answer 1

microorganisms that enter the body and cause disease, they cause communicable diseases, both plants and animals can be infected by pathogens

Question 2

what is bacteria

Answer 2

very small cells(around 1/100th the size of your body cells) which can reproduce quickly in your body
they can make you feel ill by producing toxins (poisons) that damage your cells and tissues

Question 3

what are viruses

Answer 3

viruses ARE NOT CELLS
size is around 1/100th of a bacterium
they reproduce rapidly inside your body
they live inside your cells and replicate themselves using cells’ machinery to produce copies of themselves
cell will usually burst releasing all the new viruses
cell damage caused it what makes you feel ill

Question 4

what are protists

Answer 4

single celled eukaryotes
some protists are parasites , which live on or inside other organisms and can cause damage - they are often transferred to the organism by a vector which doesnt get the disease itself (e.g insect that carries the protist)

Question 5

what is fungi

Answer 5

fungi is single celled. others have a body which is made up of hyphae (thread like structures) hyphae can grow and penetrate human skin and the surface of plants causing disease , the hyphae can produce spores which can be spread to other plants and animals

Question 6

what are the ways pathogens can be spread

Answer 6

1- water: pathogens can be picked up by drinking/bathing in dirty water(e.g. cholera is bacterial infection spread by drinking water contaminated with diarrhoea of other sufferers)
2-air-can be carried in air and breathed in. airbourne pathogens carried in air in droplets, produced when you cough/sneeze(influenza virus causes flu to spread in this way)
3- direct contact- can be picked up by touching contaminated surface- including the skin(e.g. athletes foot is a fungus which makes skin itch and flake ) most commonly spread by touching the same things as an infected person (shower floors or towels)

Question 7

viral diseases
explain measles

Answer 7

viral disease- spread by droplets from an infected person’s sneeze or cough
-causes red skin rash
-signs of fever(high temp)
-can be very fatal if complications- it can lead to pnuemonia(lung infection) or brain infection(encephalitis)

most people vaccinated against measles when theyre young

Question 8

viral diseases- explain HIV

Answer 8

virus spread by sexual contact or exchange of bodily fluids such as blood. happens when people share needles when taking drugs

virus attacks immune cells, if body’s immune system is badly damaged it cant cope with other infections or cancers so virus becomes known as late stage hiv infection or aids

it initially causes flu like symptoms for a few weeks. usually person them does not experience any symptoms for several years ,

hiv can be controlled by antiretroviral drugs=stops virus replicating in body

Question 9

viral diseases- explain tobacco mosaic virus

Answer 9

virus affecting many species of plants (e.g.tomatoes )
causes a mosaic pattern on the leaves of plants -parts of leaves become discoloured
discolouration means plant cannot carry out photosynthesis well so virus affects growth

Question 10

explain the fungal disease- rose black spot

Answer 10

rose black spot is a fungus causing purple or black spots to develop on the leaves of rose plants= leaves can turn yellow and drop off

less photosynthesis occurs, plant doesnt grow well, spreads through environment in water or by wind

gardeners treat disease with fungicides, by stripping plant of its affected leaves, leaves need to be destroyed so fungus cant spread to other rose plants

Question 11

explain disease caused by protists- malaria

Answer 11

part of a malarial protist’s life cycle takes place inside mosquito. mosquitos are vectors -they pick up the malarial protist when they feed on an infected animal. everytime a mosquito feeds on another animal, it infects it by inserting the protist into animals blood vessel
malaria causes repeating episodes of fever-fatal
spread of malaria can be reduced by stopping the mosquitos from breeding.
people can be protected from mosquitos using insecticides and mosquito nets

Question 12

explain the bacterial disease- salmonella

Answer 12

type of bacteria that causes food poisoning. those infected suffer from fever, stomach cramps, vomiting, diarrohea

symptoms caused by toxins produced by bacteria -
you can get salmonella food poisoning by eating food thats been contaminated with salmonella bacteria (eating chicken thats caught diseas whilst alive/ eating contaminated food prepared in unhygienic conditions)

in uk, most poultry given vaccination against salmonella to control spread of disease

Question 13

explain bacterial diseases- gonorrohea

Answer 13

its an std
passed on bysexual contact(unprotected sex)
caused by bacteria
person will get pain when they urinate, thick yellow/green discharge from penis/vagina
-it was originally treated with an antibiotic penicillin= its become trickier now because strains of bacteria have become resistant to it
-to prevent spread- people can be treated with antibiotics and should use barrier methods of contraception like condoms

Question 14

how can the spread of disease be reduced or prevented

Answer 14

1- being hygienic-use hygiene measures to PREVENT spread of disease, wash your hands before preparing food/after youve sneezed to stop infecting others

2- destroying vectors- organisms that spread disease,you can PREVENT disease being passed on, vectors are insecs that can be killed using insecticides,destroy their habitat so they can no longer breed

3-isolating infected individuals, isolate someone with communicale disease PREVENTS them from passing it on to anyone else

4- VACCINATION- vaccinating people and animals against communicable disease means they cant develop infection and then pass it on to someone else

Question 15

explain features of your body which makes it a good defence system

Answer 15

1-skin acts as barrier to pathogens, secretes antimicrobial substances to kill pathogens
2-hairs&mucus in nose trap particles to contain pathogens
3-trachea and bronchi secretes mucus to trap pathogens
4-trachea and bronchi sealed with cilia=hair like structures which waft the mucus up to the back of the throat where its swallowed
5-stomach produces hcl=kills pathogens that make it to the stomach

Question 16

how does your immune system attack pathogens

Answer 16

-white blood cells that travel in your blood look for invading microbes
they can engulf foreign cells and digest them=phagocytosis
-producing antibodies:
invading pathogens have molecules called antigens on its surface
-when white blood cell comes across foreign antigen - they will produce proteins called antibodies to lock onto invading cells so they can be found and destroyed by other white blood cells =antibodies produced are specific to that type of antigen

antibodies produced rapidly , carried around body to find similar bacteria/virus
if person is infected by same pathogen=white blood cell will rapidly produce antibodies to kill it = person naturally immune to that pathogen wont get ill

-producing antitoxins=these counteract toxins produced by invading bacteria

Question 17

how does vaccination prevent against future infections

Answer 17

injects small amount of dead/inactive pathogen = these carry antigens which causes your body to produce antibodies to attack them even though pathogen is harmless
e.g. MMR vaccine contains weakened version of virus that causes meales,mumps,rubella(german measles)all in one vaccine
but if live pathogens of same type appear after that, then white blood cells can rapidly mass prodcue antibodies to kill of pathogens

Question 18

what are the advantages of vaccines

Answer 18

vaccines help control lots of communicable diseases that were once common in the uk(e.g. polio, measles, whopping cough, rubella,mumpls,tetanus)

small pox no longer occurs at all and polio infections have fallen by 99%

big outbreaks of disease(epidemics) can be prevented if a large % of the population is vaccinated. even those who arent vaccinated are unlikely to catch disease bc fewer people are passing it on.

(however if a significant amount of people arent vaccinated-disease can spread quickly through them,lots of people will be ill at the same time)

Question 19

disadvantages of vaccines

Answer 19

vaccines dont alwayswork -sometimes they dont give you immunity

you can sometimes have a bad reaction to a vaccine(swelling, fever or even seizures)=bad reactions are rare

Question 20

drugs that relieve symptoms= what do pain killers do

Answer 20

painkillers (e.g. aspirin) drugs that relieve pain-they dont actuall tackle cause of disease or kill pathogens=they just help reduce symptoms

Question 21

drugs that cure=what do antibiotics do

Answer 21

antibiotics(e.g. penicillin ) kill/ prevent growth of bacteria causing problem without killing your own body cells= different antibiotics kill different bacteria, they have greatly reduced the number of deaths from communicable disease caused by bacteria

Question 22

why cant antibiotics destroy viruses

Answer 22

viruses reproduce using your own body cells which makes it hard to develop drugs that destroy the virus without killing your body cells

Question 23

how can bacteria become resistant to antibiotics

Answer 23

1-bacteria can mutate(mutations may cause them to become resistant to antibiotic)
2-if you infection, some bacteria might be resistant to antibiotic
3-when treating infection,only nonresistant strains of bacteria is killed
4- individidual resistant bacteria survives and reproduces, population of resistant strain increases
5-resistant strain can cause serious infection that cant be treated by antibiotics(e.g.MRSA= causes serious wound infections and is resistant to antibiotic meticillin)
6-to slow down rate of development of resistant strains, important for doctors to not over prescribing antibioticcs(you wouldnt get it for a sore throat)

important to finish whole course of antibiotic and not stop when you just feel better

Question 24

how did drugs originially come from plants

examples

Answer 24

plants produce variety of chemicals to defend themselves against pests and pathogens =some chemicals used as drugs to treat humans and relieve symptoms

aspirin=painkiller to lower fever=developed from a chemical from willow
digitalis= treats heart conditions=developed from foxgloves

Question 25

explain how drugs extracted from microorganisms worked

Answer 25

-alexander flemming-penicillin(mould,area around mould free of bacteria=mould was producing substabce to kill bacteria=penicillin)

now it is made on a large scale in pharmaceutical industry,synthesised by chemists in labs

Question 26

explain the 3 main stages in drug testing

Answer 26

preclinical testing
drugs tested on human cells &tissues in lab
-but to test drugs that affect whole body systems- must be done on whole animal because it has an intact circulatory system

-next step in preclinical testing-
test drug on like animals
test for efficacy, toxicity, dosage

law in britain states you should test on two live animals -some believe its cruel to test on animals but others believe this is safer to make sure it isnt dangerous for humans

Question 27

what are the 3 things to test for in preclinical testing

Answer 27

efficacy-whether the drug works and produces the effect youre looking for
dosage- the concentration that should be given,how often it should be given
toxicity- how harmful it is

Question 28

what happens if the drug passes the animal testing (double blind trial)

Answer 28

=tested on human volunteers in a clinical trial
1- Drug is tested on healthy volunteers=to make sure it doesnt have any harmful side effects when body is working normally , at start of trial -low dose of drug is given then gradually increased

2- if results on healthy volunteers is good, drugs can be tested on people suffering from illness - optimum dose is found- this dose of drug is most effective, few side effects

3- to test how well drug is works, patients randomly put into 2 groups. one is given new drug, other is given placebo (substance like drug but no effect) =allows doctor to see actual difference drug makes=allows for placebo effect(pbc patient expects treatement to work so feels better even though it does nothing)

Question 29

why are double clinical blind trials known for being blind

Answer 29

the patient in study doesnt know whether theyre getting drug or placebo- neither patient nor doctor knows until all results gathered = so doctors monitoring patients and analysing results arent subconsciously influenced by their knowledge

Question 30

what happens to the results gathered from the trials

Answer 30

results of drug testing and drug trials arent published until theyve been through peer review = helps prevent false claims

Question 31

how are monoclonal antbodies made

Answer 31

anti bodies are produced by b lymphocytes =
monoclonal antibodies are produced from lots of clones of a single white blood cell -all antibodeis are identical and targets 1 specific protein antigen
lymphocytes dont divide easily so you cant grow more

tumour cells dont produce antibodies but divide a lot= can be grown easily = fusing mouse B lymphocyte with tumour cell to create a cell called hybridoma

hybridoma cells cloned to get identical cells=produce same antibodies which are collected and purifed

monoclonal antibodies bind to anything you want, they will only bind to target-you can use them to target a specific cell or chemical in the body

Question 32

explain how monoclonal antibodies are made from a mouse’s b lymphocytes

Answer 32

1-mouse injected with chosen antigen
-b lymphocytes taken from mouse

2-fast dividing tumour cells from lab, b lymphocyte fused with tumour cell

=creates a hybridoma which divides quickly to produce lots of clones that produce the monoclonal antibodies

Question 33

how are monoclonal antibodies used in pregnancy tests

Answer 33

hormone HCG found in urine of women when pregnant
pregnancy test detect this hormone
1- part where it is urinated on has blue beads attahced
2-test strip (part of stick that goes blue when pregnant) has antibodies to the hormone stuck on to it so it doesnt move
3-if pregnant and you urinate on stick=
hormone binds to antibodies on blue bead
urine moves up stick carrying hormones and bead
bead and hormones bind to antibodies on strip
blue beads get stuck on to strip turning it blue

if not pregnant= urine moves up stick carrying blue beads, nothing to stick to blue beads so test strip doesnt go blue

Question 34

how can monoclonal antibodies be used to treat diseases

Answer 34

different cells in body have different antigens on cell surfce = you can make monoclonal antibodies that will bind to specific cells in body (e.g. just liver cells)

cancer cells have antigens on cell membrane that arent found on normal body cells(tumour markers)

in lab you can make monoclonal antibodies that will bind to tumour markers

anticancer drug can be attached to monoclonal antibodies(may be radioactive substance=toxic drug/ chemical stops cancer cells growing/diving)

antibodies given to patient through drip

antibodies target specific cells (cancer cells)
they only bind to tumour markers- side effects of antibody based drug is lower than chemo/radiotherapy side effects

drug kils cancer cells/ doesnt kill any normal body cells near the tumour

Question 35

how can monoclonal antibodies be used in labratories and research to find specific substances

Answer 35

• binds to hormones and other chemicals in blood to measure their levels
• test blood samples in labratories for certain pathogens
  -locate specific molecules on a cell or in a tissue

1- monoclonal antibodies made that will bind to specific molecules youre looking for
2-antibodies are then bound to a flourescent dye
3- molecules are present in sample being analysed then monoclonal antibodies will attach to them= they can be detected through dye

Question 36

what are problems with monoclonal antibodies

Answer 36

causes more side effects that originally expected
can cause fever, vomiting , low blood pressure so they arent as widely used as treatments by scientists

Question 37

why plants need mineral ions. what are these mineral ions

Answer 37

if there arent enough ions they suffer defiency symptoms

nitrate ions - needed to make proteins and therefore fror growth- lack of nitrates causes stunted growth

magnesium ions
needed to mak chlorophyll for photosynthesis- if there isnt enough , plant suffers from chlorosis and have yellow leaves

Question 38

how can plants get diseases

Answer 38

=can be infected by viral,bacterial,fungal pathogens, can be infested and damaged by insects, e.g. aphids are insects that can cause huge damage to plants

Question 39

what are the signs that a plant may be suffering from disease

Answer 39

stunted growth
abnormal growths (lumps)
spots on the leaves
malformed stems or leaves
patches of decay
discolouration
infestations of pests

Question 40

how can different plant disases have different signs - they can be identified by

Answer 40

1-looking up signs on gardening manual/gardening website
2- taking infected plant to labratory to identify pathogen w scientist
3- use test kits to identify pathogen with monoclonal antibody

Question 41

chemical defences that plants have

Answer 41

some produce antibacterial chemicals which kill bacteria (like mint plant or witch hazel)
otherplants produce poisons which deter herbivores(organisms that eat plants)like tobacco plants, fox gloves, deadly nightshade

Question 42

physical defences that plants have

Answer 42

-plant leaves and stem have waxy cuticle which provides barrier to stop pathogens entering
- plant cells surrounded by cell walls made from cellulose-forms physical barrier against pathogens that make it past waxy cuticle

Question 43

mechanical defences that plants have

Answer 43

thorns and hairs= stops animals from touching and eating them
-some plants have leaves that droop/curl when something touches them=they can prevent themselves from beig eaten by knocking insects off themselves and moving away from things
-some plants mimic other organisms (passion flower has bright yellow spots onleaves that look like butterfly eggs) stops other butterflies laying eggs there -several species of plant in ice plant family in southern africa look like stones and pebbles=tricks other organisms into not eating them