B6.3 Flashcards
(119 cards)
1
Q
What is a disease?
A
- condition that impairs the normal functioning of an organism on - communicable = contagious
- non communicable = non-contagious
2
Q
What does health and fitness mean?
A
- healthy = being free from disease and functioning physically and mentally
- fitness = ability to carry out an activity
3
Q
What are the causes of disease?
A
- infected by pathogen
- mutation in the organism’s genes
- organism may be effected by environmental conditions (not enough light, poor diet, lack of exercise)
4
Q
What is a pathogen?
A
- type of microorganism (microbe) that causes disease
- bacteria, Protozoa, virus, fungi
- not all microorganisms cause disease = some used to make medicines
5
Q
What are communicable diseases?
A
- spread between organisms and caused by pathogens (disease causing microorganism)
- known as infectious disease
6
Q
Give examples of types of pathogen and what they cause
A
Bacteria - animal = tuberculosis, plants = crown gall disease
Virus- animal = influenza, plants = tobacco mosaic virus
Protists (in the kingdom of Protozoa)- animal = malaria ,plants = coffee phloem necrosis
Fungi - animal = athlete’s foot, plants = powdery mildew
7
Q
What are non- communicable diseases?
A
- can’t be passed from one organism to another
- last a long time and progress slowly
8
Q
How does HIV lead to tuberculosis?
A
- HIV causes AIDs as weakens the immune system (protects against diseases)
- bacteria that cause tuberculosis are normally destroyed by immune system before symptoms can work
- but if tuberculosis bacteria infected someone with HIV = bacteria are not destroyed by the immune system so disease progress rapidly so people with HIV = more likely to show symptoms of tuberculosis
- more difficult for people with HIV to recover from tuberculosis
9
Q
How can HPV lead to cervical cancer?
A
- HPV = virus that infects reproductive system and is transmitted by bodily fluids/sexual activity
- an infection by the virus doesn’t always cause symptoms and often clears up on its own within a couple of months
- however some HPV infections can cause cell changes resulting in certain types of cancer - nearly all cervical cancer cases result from HPV infections
10
Q
Give examples of non-communicable diseases
A
- poor diet (scurry = lack of vitamin D)
- obesity (CVD/diabetes)
- genetic disorder (CF)
- body processes not operating correctly (cancer)
11
Q
What are the 4 ways infections can occur in animals?
A
- digestive system
- respiratory system
- reproductive system
- cuts in the skin
12
Q
What are droplet infections?
A
- droplets of miscues from your mouth and nose may contain pathogens which if you inhale, you catch the disease
13
Q
Describe bacteria
A
- very small (1/100th size of body cells)
- reproduce rapidly by binary fission (mitosis) (exponential growth)
- make you feel ill by producing toxins (poisons) that damage your cells and tissues
14
Q
Describe viruses
A
- not cells
- very tiny - 1/100th size of a bacterium
- replicate them self inside infected organim’s cells
- burst and then release the virus
15
Q
How do viruses take over the host cell?
A
- virus attacks cell and inserts it’s genes
- virus tells nucleus to copy its genes
- new viruses are made
- cell hurts and release new virus and destroy your cell
16
Q
Describe protists
A
- eukaryotic
- single celled and vary in size
- the protists that cause diseases at often parasites
17
Q
Describe fungi
A
- some single celled but some have body made up of thread like structures called a hyphae
- hyphae can grow and penetrate human skin/surface of plants and causes disease and can also produce spores which can spread to other animals/plants
18
Q
What is the incubation period?
A
- time between infection and feeling ill
- the pathogens reproduce and either grow and damage cells or release toxins in this time
19
Q
How can communicable diseases be spread?
A
- waterborne
- airborne
- contact
- bodily fluids
- animal vectors
- soil
- food
20
Q
How can communicable diseases be spread through water and air?
A
- water= pathogens picked up from drinking/bathing in dirty water (e.g cholera which can cause dehydration and diarrhoea)
- air = pathogens are carried in air by fungal spores (e.g Erysiphe graminis = causes barley powder mildew and decreases the plants yields)
- airborne pathogens can be carried in droplets when you cough/sneeze so other people can breathe them in (influenza virus)
21
Q
How can communicable diseases be spread through contact?
A
- pathogens can be picked up by touching contaminated surfaces (tobacco mosaic disease (caused by TMV) which makes it mottled so plants can’t photosynthesise and is spread when healthy leaves rub against infected ones)
- athletes foot = fungus which makes skin itch and flake off and spread by touching infected person (shower or towels)
22
Q
How can communicable diseases be spread through bodily fluids?
(HIV)
A
- pathogens are spread by blood (needles for drugs), breast milk and semen
- HIV = virus spread by exchanging bodily fluids, causes flu-like symptoms for a few weeks and no symptoms for several years, virus enters lymph nodes and attacks immune cells and it can’t cope with other infections/cancers = at this stage it’s known as AIDs/late HIV
23
Q
How can communicable diseases be spread through animal vectors?
A
- animals that spread diseases are called vectors
- malaria is caused by protist, and mosquitos at as vectors and they pick it up when they feed on infected animals, every time mosquito feeds = infects by inserting protists to animal’s blood vessels = malaria can cause repeating episodes of fever and can be fatal
24
Q
How can communicable diseases be spread through soil and food?
A
- pathogen live in soil =plants in contaminated soil = infected (Agrobacterium tumefaciens = causes crown gall disease are able to live freely in soil and roots of plants = galls can damage tissue and restrict flow of water through plant causing it to die)
- eating contaminated food (Salmonella = found in raw meat and if kept too long/not properly cooked = food poisoning)
25
How can we monitor disease?
- measure the incidence of a disease
- incidence = rate at which new cases occur in a population over a certain period of time
- incidence helps us see patterns (season, animal/plant vectors = better understating to come up with ways to prevent spread)
26
What is the incubation period of non communicable diseases?
- high (10yrs)
| - so give evidence of effectiveness of disease treatment/ prevention techniques
27
What factors effect communicable diseases?
- population
- poor diet
- limited healthcare
- education about the diseases
28
How can the spread of disease be reduced/prevented in humans?
- being hygienic = washing hands, covering your mouth when sneezing
- destroying vectors = kill the vectors (animal bites)
- isolating infected individuals = prevents it passing on
- vaccination or using protection = means they can’t develop it and pass it on (don’t share needles)
- clean food and drinks
29
How can the spread of disease be reduced/prevented in plants?
- plants diseases can reduce crop yields and biodiversity so important to control spread
- regulating movement of plant material = makes sure infected plants don’t come into contact with healthy plants
- destroying infected plants (burning them)= (stops source of infection
- crop rotation = many pathogens = specific to plant so changing stops pathogens becoming established
- chemical control - fungicides can be used to kill fungal pathogens or to coat bulbs before they’re planted
- biological control - dipping roots into bacterium (produces antibiotic) before planting in infected soils
30
What can a farmer do when he identifies a disease?
- burn the diseased plant to avoid spread
- treat animals with drugs or slaughter the herd
- restrict movement of livestock
- use chemical dips to kill pathogens on footwear
31
What are the causes, conditions, symptoms, spread and treatment of Athlete’s foot?
- causes = fungus (parasitic fungi called dermatophytes)
- ideal conditions = warm and humid
- symptoms = cracked, flaking and itching skin
- spread = direct/indirect contact
- treatment = anti-fungal cream
32
What are the causes, conditions, symptoms, spread and treatment of food poisoning?
- cause = bacteria creating toxins (Campylobacter (raw meat,), Salmonella (unwashed veg), E.coli (unpasteurised milk))
- ideal conditions = can survive freezing and refrigeration (killed through cooking)
- symptoms = stomach pain, diarrhoea, vomiting, fever (May lead to death)
- spread = poor food hygiene
- treatment = fluids
33
What are the causes, spread and protection of STIs?
- cause = a range of bacteria and viruses
- spread = person to person through sex or genetically contact and spreads by bloody fluids/ skin on skin (often asymptomatic) = high risk of spread
- protected = avoid sexual intercourse or use domdoms
34
What does asymptomatic mean?
- period of time where symptoms don’t show
35
What are the 4 types of STIs?
- Chlamydia
- Gonorrhoea
- Genital Herpes
- HIV
36
What are the causes, symptoms and treatment of chlamydia?
- causes = bacteria
- symptoms = pain when urinating and discharge from penis/vagina
- treatment = antibiotics
37
What are the causes, symptoms and treatment of gonorrhea?
- cause = bacteria
- symptoms = burning pain when urinating and vaginal discharge
- treatment = antibiotics
38
What are the causes, symptoms and treatment of genital herpes?
- cause = virus
- symptoms = painful blisters or sores
- treatment = no cure
39
What are the causes, symptoms and treatment of HIV?
- cause = virus
- symptoms = weakened immune system which often results in AIDs (Acquired Immune Deficiency syndrome)
- treatment = no cure but symptoms are controlled by antiretroviral drugs for life
40
How does HIV weaken the immune system?
- Human Immunodeficiency Virus
- invades the white blood cells and reproduces inside them = prevent WBC from producing antibodies
- makes the patient more susceptible to common infections
- AIDS = final stage of HIV infection where the body can no longer fight life threatening infections
41
What are the causes, effects and prevention of spread of TMV?
- plant disease caused by tobacco mosaic virus (viral disease)
- effects = mottled/Discoloured leaves as a result of virus preventing the chloroplasts from forming and if less chloroplasts = less sun energy = less photosynthesis can happen = less yields and stunted plant growth
- prevent spread= remove the inflected plant, wash hands and equipment between plantings and plant TMV resistant plant the next yr
42
What are the causes, effects and prevention of spread of crown gall disease?
- It’s a plant disease caused by agrobacterium tumefaciens (bacterial disease)
- effects = enters through wound in the plant and integrates plasmid into the plant genome = plant produces more growth chem = produces lumps called ‘galls’ and if encircles the whole stem/trunk = cuts off flow of sap = stunted growth and maybe death
- preventing spread = destroy infected plant and avoid planting susceptible plants there for 2 yrs
43
What are the causes, effects, spread and prevention of spread of powdery mildew ?
- it’s a plant disease caused by a range on fungi (fungal disease)
- effect = white powdery spots on leaves and stems = less growth and leaves drop early to less yield
- spread = more humid and moderate temp and favourable and survives on plant residues between seasons and releases spores which can be spread by winds to other plants
- preventing spread = spread with fungicide (chem to kill fungi)
44
What two types of barriers do plants have against diseases?
- physical = physical barriers preventing the microorganisms from entering (waxy cuticles, cell wall, callose)
- chemical = substances secreted by the plant to kill microorganisms (antimicrobial chemicals, resistance genes)
45
How do waxy cuticles protect a plant against pathogens?
- a waxy substance that covers the epidermal of most parts of the plant
- prevents water loss and pathogens becoming in direct contract with the epidermal cells = chance of infection by pathogens transferred in water is reduced
- hydrophobic = prevents water from collecting on the surface and fungal spores from germinating
46
How do cell walls protect a plant against pathogens?
- made from cellulose fibres (strong and flexible)
- defence against bacterial and fungal pathogens as it forms good structural barrier
- plant cell has primary cell wall for structural support as cellulose fibres are cross linked with other substances (pectin) which forms a gel to cement neighbouring cells together
- many calls have 2nd cell wall which develops inside primary
47
What happens when pathogens get past waxy cuticle and cell wall?
- triggers the cell wall to produce callose
| - it gets deposited between cell walls and membrane and reinforces the cell wall
48
What are the chemical defences of plants?
- produce antimicrobial chemicals or kill pathogens/ inhibit their growth (antibacterial chemicals)
- antimicrobials are chemicals that act against microbes
- produce saponins (destroys cell membrane of fungi/other pathogens)
49
What do the chemical defences citronella and pine resin do?
- act as insect repellents
50
What does the chemical defences pyrethrins do?
- insecticides (kill insects that come into contact)
51
What do the chemical defences phenols and defensins do?
- phenols disrupts the cell wall
- defensins disrupt cell membrane
- both act as antibacterial compounds
52
What do the chemical defences chitinases and caffeine do ?
- chitinases = break down chitin in fungal cell walls
- caffeine = toxic to fungi and insects
- both anti-fungal compounds
53
What does the chemical defences cyanide do ?
- toxic to all living things that come into contact (including humans)
54
What are the chemical produced by plant defences used for?
- basis for modern medicine and drugs are synthesised by chemists in labs but the process starts with a chemical extracted from a plant
- genes responsible for some of these chemicals are used for genetic engineering of insect and disease resistance crops
55
What are the 2 field techniques to diagnose plant diseases?
- observation
| - microscopy
56
How can observation be used to identify plant diseases?
- look for visual symptoms
- growths (crown gall disease)
- mottling (tobacco mosaic disease)
- rotting
- deposits
- maybe touch or smell
57
How can microscopy be used to identify plant diseases?
- used to identify smaller features such as the pathogen
| - most cases might microscope is sufficient but for more accurate diagnosis = use electron microscope
58
What is the disadvantage of field techniques?
- plant disease can only be identified in the field one symptoms are apparent and the infection has already taken hold
59
What are the 2 lab techniques to find pathogens of plant diseases?
- DNA analysis (PCR)
| - Antigen identification (ELISA test)
60
How can DNA analysis / PCR be used to identify pathogens of plant diseases?
- all living things have a unique genome
- use DNA fingerprinting to identify the pathogen we have based on the DNA present
- parts of the DNA complementary to the pathogen are used as primers (template) and any dna that matches is copied over and over again and if the pathogen is present lots of its dna will be made and it will show up on images
- match the bands from bottom up for known viruses and unknown pathogens
61
How can antigen identification be used to identify pathogens of plant diseases?
- antigens are protein spikes on the surface of a microorganism
- specific pathogens have specific antigens
- antigens can be identified using chemical analysis
62
What is a ELISA test?
- antigens are unique molecules on cell’s surface and can be detected using antibodies (proteins that bind to specific antigen)
- antigens from pathogen = present if infected by it
- in ELISA = antibodies for the pathogen’s antigens are used as they have enzymes on them which react with substrate = colour change
- antibodies are added to sample tested and watched, but if bind to antigen, stay in sample so colour change when substrate is added = antigen (and so the pathogen) is present
63
What is the advantage of lab techniques?
- lab tests allow for the identification of a pathogen before significant damage has been created
64
What are scabs?
- platelets change fibrinogen into fibrin to form a network of fibres
- red blood cells get trapped in fibres forming a clot = clot hardens to make a scab
65
What are the defence mechanisms of the human body?
- skin
- stomach acid
- Cilicia and muscus
- airways (respiratory tract)
- nasal hairs
- tears
- platelets
66
How does the skin act like a defence mechanism?
- it acts as a physical barrier
- dry dead cells make it hard for the microbes to penetrate
- sweat glands produce oils that help kill microorganisms
67
How does stomach acid act as a defence mechanism?
- kills pathogens present in contaminated food and drink
| - produced HCl
68
How does the respiratory tract act as a defence mechanism?
- nasal passage - keeps out dust and microorganisms
- Cilicia and muscus - muscus trans microorganisms before the cilia waft the muscus up to the top of the throat, where it’s swallowed
69
How do the eyes act like a defence mechanism?
- produce tears
| - in tears you have enzyme lysozyme which breaks bacteria down on the surface of the eye
70
How do the blood vessels like a defence mechanism?
- platelets in the blood clump together to plug the damaged area = blood clotting (stops you from losing blood and prevents microorganisms entering)
- platelets = tiny fragments of cells that have proteins on the surface to help them stick together to the side of the wound
71
What are the 2 types of white blood cells?
- phagocytes - carry out phagocytosis = engulf and divest organisms (multiple nucleus)
- lymphocytes - produce antibodies/anti toxins (larger single nucleus)
72
What is there on the surface of a pathogen?
- protein spikes called antigens
| - correspond to antibodies on lymphocytes
73
How do wbc consume pathogens?
- phagocytes have a flexible membrane and have lots of enzymes
- enables them to engulf foreign cells and digest them-
- phagocytosis
74
How do wbc produce antibodies?
- done by B-lymphocytes
- every invading pathogen has unique antigens on its surface
- wbc comes across foreign antigen = produce proteins called antibodies to lock onto the invading cells
- antibodies are specific to that type of antigen
- antibodies are produced rapidly and carried around the body to lock on to similar pathogens
- antibodies help the phagocytes find pathogens so they can engulf them
- some wbc are called memory cells - stay around in the blood after pathogen is gone so if the person is infected with the same pathogen again = the white blood cells rapidly produce the antibodies to destroy it - naturally immune to that pathogen
75
What is immunity
- if the same pathogen infects you a 2nd time, your body responds faster and can eliminate the pathogen
76
How does the wbc produce antitoxins?
- counteract toxins are produced invading bacteria
77
What are monoclonal antibodies?
- produced from lots of clones of a single white blood cell = identical and will only target one specific protein antigen
- produced in the lab by using hybridomas (fusion of lymphocyte and tumour cell)
78
Why are hybridomas used?
- fusion of myetomas (cancer cells) and lymphocytes
- cloned to get lots of identical cells which can all divide to produce the same antibodies (monoclonal antibodies)
- can be collected and purified
79
Why are monoclonal antibodies useful?
- they can bind to anything you want
- e.g an antigen found on only one type of cell so will only bind to that target molecule
- so can target specific cell/chemical and kill/ prevent it
80
How are monoclonal antibodies produced?
- genetically modified mice injected with chosen antigen
- body produces antibodies to specific antigen (using lymphocytes)
- lymphocytes collected and fused with myeloma cells to make hybridoma (can’t survive out of body)
- myeloma cells reproduce indefinitely
- as hybridoma cells reproduce = form clones
- each clone will produce required antibody which is harvested = monoclonal antibodies
81
How can monoclonal antibodies be used in pregnancy tests?
- HCG = produced 2 weeks after conception
- monoclonal antibodies that bind to hcg in urine have been produced causing a colour change
- where you wee= blue bead has antibodies attached
- if pregnant = hormone bind to antibodies on the blue beads and urine moves up the stick, carrying hormone and beads up and beads and hormone bind to antibody on strip and blue beads get stuck = turning it blue
- if not, using move up but no colour change as no blue beads
82
How can diseases be detected with monoclonal antibodies?
- cancer cells antigens are called tumour markers and you can make monoclonal antibodies that bind to it to confirm presence
- allow early diagnosis of disease (prostate cancer)
83
How can cancer be diagnosed with monoclonal antibodies?
- Prostate cancer
- antibodies are labelled with radioactive element
- labelled antibodies are given to patient through a drip (go into blood and are carried around body)
- when antibodies come into contact with cancer cells, they bind to the tumour markers
- picture of the patient’s body is taken using a special camera that detects radioactivity (cancer cells = bright spot)
- doctors can see where, what size and spread of cancer (if it’s beyond prostrate gland)
84
How can cancer be treated with monoclonal antibodies?
- monoclonal antibodies target specific cells which result in death/prevention so:
- anti-cancer drug is attached to it (might be radioactive substance or toxic drug which stops cancer cells growing and dividing)
- antibodies target specific cells as only bind to tumour markers
- drug kills the cancer but not the normal body cells
85
Why is treating cancer with monoclonal antibodies better than other treatments?
- radiotherapy and chemotherapy can affect normal body cells as well as killing cancer cells
- radiotherapy = firing high - energy beams (X-rays) at tumour
- chemotherapy = using chemicals to destroy tumour
- side effects of an antibody based drug are lower than radio/chemotherapy
86
Why do we get vaccinated against diseases?
- when you’re infected with a new pathogen, it can take your wbc a while to produce the antibodies needed to deal with it
- in that time you can get very ill or die
87
How do vaccinations work?
- they involve injecting dead, inactive or weakened pathogens into the body
- they carry antigens so even though they are harmless, they still trigger an immune response
- the wbc (lymphocytes) produce antibodies to attack them
- some of theses wbc remain in the blood as memory cells so if live pathogens of the same type ever appear, the antibiotics help destroy them will be produced immediately before symptoms show = immunity
88
How can epidemics be prevented?
- if a large percentage of the population is vaccinated
- so even people who aren’t vaccinated are unlikely to catch the disease as fewer people to pass it on
- but if significant number aren’t then the disease can spread quickly through them and lots of people will be ill at the same time
89
What diseases should you be immunised against up to 1 yr old, 3-5 yrs, 10-14 yrs, 12 - 13 yrs and 13-18 yrs?
Up to 1 = polio, tetanus, laugh, diphtheria, meningitis, mumps, rubella
3 - 5 = MMR, polio, diphtheria, whooping cough
10 - 14 = tuberculosis,Isis /p(TB)
12 - 13= HOV (girls only)
13 - 18= polio, diphtheria, tetanus
90
What are drugs?
- substances which alter the way the body works (some medically used - penicillin and some dangerous if misused)
- this is why some can’t be bought over the counter and only on prescription
91
What are antibiotics?
- drugs that kill bacteria without killing your own body cells (diff types for each range of bacteria)
- many produced naturally by fungi or other microbes (penicillin = mould)
- grown at large scale and useful for clearing up bacterial infections but don’t kill viruses (not all microbes are harmful)
- some bacteria are naturally resistant to antibiotics so misuse has increased the rate of development of resistant strains and MRSA is the best-known antibiotic resistant strain
92
How can the bacteria be identified?
- using blood/stool samples sent to labs
| - cultures are grown on an agar plate and then antibiotic discs are used to identify which drug would work best
93
What is the zone of inhibition
- region where bacterial growth is prevented around the disc of antibiotic
- large zone = antibiotic has a greater effect on killing the bacteria
- area of circle = pi x r squared
- radius = half x diameter of circle
94
What are antivirals?
- drugs that destroy viruses (specific so act on 1 type of virus) and most stop them from reproducing
- might kill virus by = blocking virus from entering host cell, prevent virus from releasing its genetic material and prevent virus from inserting its genetic material in to host DNA
- difficult to produce as virus use the host cell to replicate so hard to target virus without damaging cell
95
What are antiseptics?
- chemicals that destroy microorganisms or stop them from growing and don’t harm human tissue (alcohol and iodine) = diff antiseptics for diff microorganisms
- used in external living surface (to kill/ neutralise any type of pathogen) to help clean wounds and surfaces (prevent infection rather than treat it) and kills pathogens on non-living surfaces =disinfectant (household products)
- used in hospitals and surgeries to try to prevent the spread of infections like MRSA
96
What are aseptic techniques?
- prevents foreign microorganisms from being introduced to a test sample
- ensures that the apparatus and environment stay sterile
- contamination can affect the results and potentially result in growth of pathogens
97
What should you do with the workspace where you’re working?
- wash working areas with alcohol before and after work which ensures that no microorganisms are present within the area
- do it regularly but it can be dangerous as alcohol is flammable
98
What should you do if you’re working with pathogens?
- wear gloves so it prevents no microorganisms passing from sample to skin
99
What should you do when working with glassware and apparatus?
- sterilise all glassware/ apparatus (foreceps) before and after use
- in autoclave (a machine which steams equipment at high pressure)
- prepared agar jelly should also be put through the autoclave
100
Why should you work near a Bunsen burner?
- it prevents microorganisms falling into an open sample
| - this is as hot air rises, microbes in the air are drawn away from the culture
101
What should you do to the glass container of bacteria after it’s opened?
- briefly flame the neck of the glass container of bacteria just after its opened and just before its closed
- this causes air to move out of the container, preventing unwanted microbes from falling in
102
Why and how should you sterilise a wire loop?
- before using wire loop to transfer microorganisms from one medium to another it needs to be sterilised
- heat in the Bunsen flame until red and then cool it close to the flame, away from the bench
103
How can identify bacterial colonies?
- sterilise loop and take a sample
- make 4 to 5 steaks across one edge
- flame and cool loop to kill off anything still on there
- turn plate and make 4 to 5 new streaks
- repeat 3 and 4 twice more and don’t join the lines together
- incubate the plate
- bacteria can be identified by looking at the colony shape, edge, colour, surface appearance and elevation and further chemical tests can be carried out to identify the colony
104
How can we investigate antimicrobials? (Testing the action of antibiotics)
- pour hot sterilised agar jelly into a sterile Perti dish
- when jelly cooled = inoculating (wire) loops can be used to transfer microorganism into culture medium or a sterile dropping pipette and spreader to get an even covering of bacteria
- take 3 discs of filter paper and soak one is antibiotic A, second in B and C is a control and should be soaked in sterile water
- place discs on jelly using sterile forceps and tape lid into dish to prevent contamination by microbes = antibiotic will diffuse (soak) into agar jelly
- leave space b/w discs and label them and leave dish for 48 hrs at 25 C and the bacteria will multiply and grown into a lawn covering the jelly
- anywhere bacteria can’t grow = clear zone so more effective the antibiotic is against the bacteria = large the clear zone around paper disc
105
Why should you use a control disc?
- so you can be sure that the different between the growth of the bacteria around the control disc and antibiotic discs is due to affect of the antibiotic alone (and not something weird in paper etc)
- need to also control temperature (don’t leave near radiator etc), disc size
106
What temperature is culture of microorganisms are kept at?
- about 25 C because harmful pathogens aren’t likely to grow at this temp
- in industrial = cultures are incubated at higher temp so they can grow a lot faster (no pt too high or enzymes in microorganisms could be denatured)
107
What does no clear zone mean?
| What is the jelly?
- that bacteria is resistant to it
- jelly is a culture medium as it contains carbohydrates, minerals, proteins and vitamins that microorganisms need to grow
108
How can you compare antimicrobials?
- can compare effectiveness on bacteria by looking at relative size of clear zones
- large the clear zone = more effective
- can check by eye or for more accurate= calculate area using their diameter (include the area of the disc and don’t open Petri dish to measure clear zone as it should be visible through bottom of dish)
- use area = pi x r (diameter/2) squared (diameter with ruler)
109
How are new drugs discovered?
- drugs may come from plant extracts
- first need to go through pre-clinical trials, which usually involve computer simulations, testing on human cells and tissue and then animals
110
What software is used to develop possible drugs?
- computer modelling can be used to develop possible drugs
- they can produce list of compounds that target certain condition
- a computer software stimulates a human’s response to a drug so you don’t need to test on live animals at this stage
- not as accurate as testing the affect on a live organism
111
What happens once a potential drug is identified?
- drugs are developed further by preclinical tests in the lab to see how it behaves
- preclinical tests = test on live cells, bacteria and tissue culture
- but you can’t use human tissue to test drugs that affect whole/ multiple body systems
- e.g testing drug for blood pressure must be done with a whole animal (one with intact circulatory system)
- many fail as this stage as may damage cells or not work
112
What happens after clinical trials?
- Animal testing =must pass with 2 species before human trials (some think it’s cruel and others think it’s the safest way)
- 3 Rs principal:
- reduction = use small number of animals present
- refinement = improve experiments to avoid unnecessary suffering and improve animal care
- replacement = replace animals with other techniques (e.g cell cultures)
113
What happens after animal testing?
- clinical trials
- so drugs are tested on humans
- first = tested for safety on healthy volunteers so it doesn’t have any harmful side affects as sick people are more vulnerable to the damage it could do
- second = small sample (few 100) volunteers with the condition (used to test effectiveness)
- third = large number of volunteers (several 1000) with condition (used to test safety and effectiveness)
114
Why do human trials take so long?
- in some cases, the drug takes a while to have the effect it was designed for (e.g treating cancer)
- it’s also important to find out if drug has any side effects which may appear after a long time
115
What happens if the drug passes the human trials?
- approved by MHRA (medicine and healthcare products regulatory agency)
- after approval, the drug is monitored in case of any side effects when mass produced
116
What are the two types of groups of patients in a clinical trial?
- one is given new drug and other is given a placebo (substance that looks like the real drug but doesn’t do anything)
- this is done so scientists can see actual difference the drug makes, allowing the placebo effect
- they are double blind trials so the patient and scientist/ doctor don’t know if they’re getting the drug or the placebo until the all the results have been gathered
117
Why is the double blind trial used?
- so doctors monitoring the patients and analysing the results aren’t subconsciously influenced by their knowledge
- to allow for the placebo effect in patients (where people start to feel better just because they expect the treatment to work even though the treatment isn’t doing anything)
118
When are placebos not used?
- if the patients are seriously ill as it’s unethical not to allow all patients to get the potential benefits of the new drug
119
What do scientists sometimes compare results of drugs to (except placebos)?
- sometimes compare results with the best existing treatment rather than a placebo
- this tells them how the drug compares to what we already have
