Germ theory
Learning Objective:
To be able to evaluate evidence for germ theory.
Lesson Outcomes
Vocabulary
Germ theory
Could be able to explain how each
discovery fed into a bigger picture
understanding of infectious
disease.
Should be able to describe the
discoveries each scientist
made.
Must be able to identify key
scientists involved in
developing our understanding
of ‘germ theory’
Skills being used in this lesson:
Listening
Presenting
Problem Solving
Creativity
Staying Positive
Aiming High
Leadership
Teamwork
Virtue linked to this lesson:
Good temper
Ignaz Semmelweiss
Semmelvweiss was investigating the cause of deaths
from childbed fever.
• He noticed that maternity wards that had more
midwives than doctors had lower death rates.
• He then noticed that the doctors would conduct
autopsies and then, without washing their hands,
would go to work on the maternity wards.
• The midwives did not conduct autopsies.
• He got all the staff to wash their hands with
chlorinated hand wash and the deaths
decreased.
https://www.youtube.com/watch?v=KSLCkT2ttXQ
Cholera and John Snow
After observing
Cholera outbreaks,
John Snow did not
believe the cause
of the disease was
miasma
Part 1: https://www.youtube.com/watch?v=TLpzHHbFrHY&t=6s
Part 2: https://www.youtube.com/watch?v=1jlsyucUwpo
Part 3: https://www.youtube.com/watch?v=9NVT6iZP2qg&t=25s
John Snow and Cholera
All residents who’s drinking water well is down hill of the sewage runoff down the street got ill
and most of those who’s well is uphill of the sewage run off were fine.
John Snow noticed that those who's water came from Southwark
and Vauxhall water company got ill, but those who got their
water from Lambeth were fine
Direction of river flow
Southwark and Vauxhall drew their drinking
water from downstream of a sewage outlet
Only 8 deaths
outside the area
closest to the Broad
st pump.
3 were children who
went to school near
Broad st
3 were workers who
also stopped at the
Broad st well
The workhouse was close to the
Broad st pump, but did not have
many deaths. John Snow found out
they had their own private water
pump from a safe water works
The Broad
street pump
There were few
deaths at the Brewery
close to the Broad st
pump, but, John
discovered that they
only drink beer
(alcohol kills bacteria)
Joseph Bazalgette’s Sewers
https://www.youtube.com/watch?v=cba7di0eL8I
Louis Pasteur
https://www.youtube.com/watch?v=OXdbQ1JkX7c
Joseph Lister
In 1861, Lister observed that 45
to 50 percent of amputation
patients died from sepsis.
In 1865, he learned of Louis
Pasteur's theory that
microorganisms cause infection.
Using phenol as an antiseptic,
he reduced the mortality rate in
his ward to 15 percent within four
years. https://www.youtube.com/watch?v=Vg1hqZanDa0
https://www.youtube.com/watch?v=4ZvaeugsRPU
Comparing healthcare then and now
1800s
Pain relief for
patients
Hand cleaning
Uniform
Cleanliness of
surgery
Cleanliness of
equipment
Death rate
2000s
Then and Now
• 1800s Surgery
–
–
–
–
–
–
–
No anaesthetic
No hand cleaning
No clean clothes
Sawdust on floor
No implement cleaning
No cleaning of table
High death rate from
disease
Then and Now
• 2000s Surgery
–
–
–
–
–
–
–
Sterile implements
Hand cleaning
Clean clothes
Face and hair masks
Sterile gloves
Sterile bed sheets
Clean room (no
sawdust)
Hypothesis
This investigation will look at the effect of disinfectant on
bacteria.
• Agar plates covered with bacteria can be used to test
substances to see if they have antiseptic properties.
The test substance can be placed in a hole in the agar
or paper discs soaked in the test substance can be
placed onto the bacteria-covered agar. If the substance
kills bacteria, they won’t grow in the area near paper
discs or the holes.
• You are going to test the hypothesis that:
The higher the concentration of an antiseptic, the better
it is at killing bacteria.
Equipment
Equipment
•
•
•
•
•
•
•
•
Mouthwash,
measuring cylinder,
beakers,
agar plate which contains
the bacteria and has six holes,
marker pen,
dropping pipette,
sticky tape,
distilled water
How will it be used to test the hypothesis?
Control variables
Autoclave: https://www.youtube.com/watch?v=NTUp_U22gNo
What will you keep
the same?
•
•
•
•
•
Distilled water
Agar nutrient Jelly
Antiseptic
Well size
Same species of
bacteria
• Same amount of
disinfectant solution
in each well
• Temperature
(incubation)
How will you keep it
the same?
Why will you keep it
the same?
Risks
What harm/ injury could happen
to you?
How can you prevent yourself/
others being harmed/ injured?
Overall plan
Method (overall plan)
1. Make up some different concentrations of mouthwash by
mixing mouthwash with water in the beakers. Carefully
label each beaker with the concentration that it contains.
2. Use the marker pen to write on the bottom of your agar
plate, which of the concentrations of mouthwash is to be
added to which hole.
3. Now add some drops of each mouthwash concentration
to the holes in the agar in the dishes.
4. Tape the lid onto your dish like this:
5. Give your plate to your teacher, who will put it in a warm
place for 24–48 hours.
6. Measure the diameters of the clear areas around the
holes in the agar plate. You could measure them at two
different times.
Results
Independent variable:
concentration of antiseptic
Units measured in? %
Dependent variable: diameter of
area with no bacteria
Units measured in? mm
Test 1 Test 2 Test 3 Average
0%
0
0
0
20%
5
6
4
40%
11
11
13
60%
19
23
24
80%
27
27
28
100%
31
29
30
Average Dependent variable (units)
Processing and presenting your results
Independent variable (units)
Secondary data
Dettol
Diameter of the area around the filter paper disc
disinfectant
without bacteria growth (mm)
concentration
1st
Generation
2nd
Generation
3rd
Generation
4th
Generation
25%
32
33
32
31
50%
37
38
35
37
75%
48
46
50
49
Pathogens
Learning Objective:
To be able to evaluate problems and diseases caused by pathogens.
Lesson Outcomes
Vocabulary
Pathogen
Could be able to explain how signs
of a disease can be used to
identify the pathogen.
Should be able to describe
some problems and diseases
caused by bacteria.
Must be able to describe
diseases caused by different
pathogens.
Skills being used in this lesson:
Listening
Presenting
Problem Solving
Creativity
Staying Positive
Aiming High
Leadership
Teamwork
Virtue linked to this lesson:
Good temper
Starter Activity
• Write down the names of any
diseases you know or must have
heard of.
• Is the disease infectious or not?
• What were they caused by?
A microorganism that
causes disease is called a
Pathogen.
Keywords:
Micro-organism, Microbe, Bacterium (bacteria), Virus (viruses), Pathogen , Infectious
Bacteria
• Are very small cells
• Reproduce rapidly in your
body
• Make you ill by- damaging
cells and producing toxins
Cell Wall
Cell
Membrane
Chromosome
Cytoplasm
NO true nucleus
Viruses
Protein Coat
• Viruses are not cells.
• They replicate
themselves by invading
your cells.
• The cells burst and
release the new virusesthis makes you feel ill!
Genetic Material
Tail
NO true nucleus, NO cytoplasm
Bacteria – The Key Points
•
•
•
•
•
-
Are living cells
Can multiply very rapidly
Up to 0.01mm long
Release toxins or poisons
that make us feel unwell
Examples include:
Food poisoning
Cholera
Gonorrhoea
KS3 CHECK: What are the
main components of a
bacterial cell?
Viruses – The Key Points
• Are NOT living cells – they have no
nucleus (RNA inside protein coat)
• Are even smaller than bacteria
• Can ONLY reproduce inside our cells
• The virus enters the cells, makes lots of
copies and then they burst out of the
cell into the bloodstream
• Examples include:
- Flu (Influenza)
- Colds
- AIDs
- Chicken Pox
SARS
Bacteria and Viruses
Tetanus
leprosy
Diabetes
Cold sore
Tuberculosis
Syphilis
Chickenpox
Influenza
Typhoid fever
Cholera
AIDS
HIV
Picture 2
Picture 1
Bacteria
Picture 3
Virus
Pathogen Attack
BACTERIA
VIRUS
Bacteria do their damage OUTSIDE
of the cell.
Viruses do their damage INSIDE of
the cell.
They do not need to get into the
cells to cause damage.
They MUST get into the host cell to
cause damage.
How microbes make us feel ill
Bacteria
Viruses
1.
2.
T = toxin
3.
Comparing sizes...
You are the size of Europe
A fungus is the size of a
football pitch
A bacteria would be the
size of a bus
A virus would be the size of a football
COMMUNICABLE DISEASE
Virus lifecycle- the Lytic cycle
https://courses.lumenlearning.com/microbiology/chapter/the-viral-life-cycle/
Virus attached
to cell
membrane/
wall
Virus injects its
DNA inside cell
Cell copies the
virus DNA
More viruses
are made
Viruses ‘burst’
out of the cell
to begin the
cycle again.
Investigation – 10 min
Aim: We are going to take swabs of different
parts of the lab to see what microbes we
can find.
Apparatus
Sterile swabs
Agar dishes
Permanent pen to label
cellotape
Physical and chemical defences
Learning Objective:
To be able to explain how sexually transmitted infections (STIs) are
spread and how this spread can be reduced or prevented.
Lesson Outcomes
Vocabulary
Barrier
Could be able to explain how the
spread of the STIs Chlamydia and
HIV can be reduced or prevented.
Should be able to explain how
physical and chemical barriers
protect the body.
Must be able to provide
examples for physical and
chemical barriers.
Skills being used in this lesson:
Listening
Presenting
Problem Solving
Creativity
Staying Positive
Aiming High
Leadership
Teamwork
Virtue linked to this lesson:
Good temper
How does our body protect us?
• On your piece of paper draw
around a group member and label
all the places pathogens can enter
the body.
• Then write what that part of the
body does to try and prevent their
entry
• Try to give an explanation of how
each works
(5 minutes)
Physical
barriers
Chemical
barriers
Biological
barriers
•
•
•
•
•
Hair
Cilia
Mucus
Skin
Blood clotting
• Stomach acid
• Lysosomes and
acid secreted
through skin
• Saliva
• Urine
• White blood
cells
• Enzymes
• Gut flora
Eyes
Respiratory tract
Digestive tract
Stomach acidity
https://www.youtube.com/
watch?v=IWMJIMzsEMg
Starter:
Skin
Low pH
Anatomic barrier
Sweat, sebum
Antimicrobial
secretions
Genitourinary
tract
Washing by urine
Vaginal lactic acid
47
Respiratory tract
Mucus
Ciliated epithelium
Phagocytosis
Digestive tract
Mechanical flushing
Stomach acidity
Alkaline pH in the
colon and ileum
Bacteriocins (colon)
Proteinaceous toxins produced by bacteria to
inhibit the growth of similar or closely related
bacterial strain(s).
Eyes
Washing by tears
Lysozyme
Skin
Low pH
Anatomic barrier
Sweat, sebum
Antimicrobial
secretions
Genitourinary
tract
Washing by urine
Vaginal lactic acid
48
Immune system
Learning Objective:
To be able to explain the role of antibodies in the immune system.
Lesson Outcomes
Vocabulary
Lymphocyte
Could be able to explain how
immunization protects against
infection by a pathogen.
Should be able to explain the
role of antibodies in the
immune response.
Must be able to describe how
the immune system protects
the body by attacking
pathogens.
Skills being used in this lesson:
Listening
Presenting
Problem Solving
Creativity
Staying Positive
Aiming High
Leadership
Teamwork
Virtue linked to this lesson:
Good temper
Immune response
https://www.youtube.com/watch?v=jzFDGz-bjcM
Antibodies
Antigens
The cells in our body contain
antigens, these are your body’s way
of telling which cells are your own,
and which cells are unwanted
invaders.
Bacteria or viruses, have different
shaped antigens from yours, and your
body can tell that they don’t belong.
antigen
cell
red
blood
cell
Antibodies
• One type of white
blood cell is called
a lymphocyte –
these white blood
cells are
responsible for
killing bacteria by
producing
antibodies
Antibodies
Each different type of microorganism causes a different
type of antibody to be produced. Antibodies are Y shaped
proteins made by white blood cells.
An antibody can only bind to the micro-organism that
caused it to be produced. They are specific.
Antibodies are specific to the microbe that
they destroy (like keys)
http://www.youtube.com/watch?v=lrYlZJiuf18&feature=related
These are molecules which are shaped
to fit onto invaders’ antigens. They stick
them together so they can’t move and
they can be engulfed by phagocytes
Task: Match up the antibody with its microbe.
Then explain how the white blood cell
recognises the microbe.
Antibodies
A small number of these white blood cells stay
in the blood after the first infection.
Phagocytosis
• One type of white
blood cell is called a
phagocyte – these
white blood cells are
responsible for
killing bacteria by
surrounding and
ingesting them.
• They DO NOT EAT
the pathogens
Digestion
1 mark for
correct steps
Step 1
Some of the cells around the wound
secrete chemicals that act as a signal
to tell the phagocyte it is need.
Step 2
The phagocyte detects the bacteria
and engulfs it.
Step 3
The lysosome found in the bacteria
fuses to the bacteria which contains
acidic enzymes and toxic chemicals.
The enzymes digest the bacteria and
absorb any useful products and
expels the rest.
Step 4
1. Pathogen infection enters
body
2. Lymphocyte white blood
cells work out which
antibodies to make
3. Antibodies immobilise
pathogen
4. Phagocyte white blood
cells digest the pathogen
5. Memory Lymphocytes
(white blood cells) stay in
the body remembering
how to fight the infection
quickly if it invades again.
How do we
develop our
immunity?
Pathogen
Draw a cartoon strip to
explain how our
immune system fights
infection
Keywords:
Micro-organism, Microbe, Bacterium (bacteria), Virus
(viruses), Pathogen , Infectious
Review: Put the stages of immunity in the right order
The immune
system
remembers how
to make the right
antibodies, and
the pathogen is
killed more
quickly.
The same
pathogen tries
to infect the
person again.
A pathogen
like chicken
pox virus
enters the
body.
The white blood
cells of the
immune system
create
antibodies,
antitoxins which
destroy the
pathogens.
The person is
now immune
to the
pathogen, and
is unlikely to
get the same
illness again.
The pathogen
secretes
toxins, which
make the
person feel ill.
Answers
1
A pathogen
like chicken
pox virus
enters the
body.
4
The same
pathogen tries
to infect the
person again.
2
3The white blood
The pathogen
secretes
toxins, which
make the
person feel ill.
cells of the
immune system
create
antibodies and
antitoxins which
destroy the
pathogens.
5 The immune
6The
system
remembers how
to make the right
antibodies, and
the pathogen is
killed more
quickly.
person is
now immune
to the
pathogen, and
is unlikely to
get the same
illness again.
Primary and Secondary Infection
• As part of your trainee doctor role
you have been monitoring a patients
blood over 90 days to understand
how the concentration of antibodies
change.
• Plot a graph to show what happens
to the concentration of antibodies in
the blood when a person is infected
twice by a MO
Days
0
5
10
15
20
25
30
35
40
45
Concentration of
antibodies
0
3
5
7
20
25
15
10
5
5
Days
50
55
60
65
70
75
80
85
90
Concentration of
antibodies
4
4
4
4
15
25
40
50
45
Plot this data in a graph to help
you analyse it accurately
Analysing the results
• The first infection occurred at day 0, the
second infection occurred at day 70.
• What do you notice about the number of
antibodies in the 2 separate infections?
• Can you think why this might be?
Describe what is happening at stages A – E, do this
on your graph.
6 MARKER PRACTICE
Diane has been to the doctor to try and find out why she
feels so unwell. The doctor has told her that she needs to
have some tests done to see what type of pathogen may be
causing the problem. The doctor says that in the mean time
her body will do a pretty good job of stopping her feeling ill
without any medicine.
Can you explain to Diane what the doctor means by
pathogens, and how her body is going to make her better.
Immunisation
Learning Objective:
To be able to explain how vaccinations create immunity to a particular
pathogen
Lesson Outcomes
Vocabulary
Vaccination
Could be able to evaluate claims
about controversial vaccines in the
media
Should be able to describe the
action of vaccinations and how
it leads to immunity.
Must be able to define the
term immunity
Skills being used in this lesson:
Listening
Presenting
Problem Solving
Creativity
Staying Positive
Aiming High
Leadership
Teamwork
Virtue linked to this lesson:
Good temper
Edward Jenner
https://www.youtube.com/watch?v=yqUFy-t4MlQ
What is a vaccine?
Vaccines create immunity without making you
sick
Vaccines contains
• dead pathogens, or
• live but weakened pathogens, or
• parts of the pathogen
The white blood cells respond to the vaccine as if it
were a disease by creating antibodies.
Quick questions:
1. Why do we need different vaccines for different
diseases?
2. New flu vaccines must be made every year. Why?
How do vaccines work?
https://www.youtube.com/watch?v=SduMbjW2V9A
A small number of these antibodies
remain in the blood after the vaccination.
1
2
3
6
5
4
Apply your knowledge
• Thinking back to your immunity graph – can
you now explain how a vaccine works?
Herd immunity
What do you know about MMR or HPV? What
do you know about vaccines?
Vaccines and Autism
• In 1985, a doctor found a link
between children getting
vaccines and being diagnosed
with autism
• Afterwards, it was found that he
was paid to falsify the results
• Since then, thousands of studies
have found NO link
The MMR Debate
There is a link between the MMR vaccination and
autism.
Proof: This graph shows that autism rates grew in
California after the MMR vaccination was introduced.
The MMR Debate
Result: Less children were vaccinated.
The MMR Debate
Lets look at that data again….
It appears to show more cases of autism being diagnosed each year. In
fact, it shows all people registered as having autism in a single year, 1991,
plotted by year of birth. It does not account for the rise in California’s
population, changes in how autism was diagnosed and a trend to diagnose
children at an earlier age, which might explain the apparent rise in cases.
The MMR Debate
In 2007 it was proved that there is no link between MMR
and autism. All the studies that were used as proof were
flawed.
One, carried out by a British Doctor was based on 12
autistic children who he paid to take blood from at his son’s
birthday party. He was also being paid for advising
solicitors on legal action by parents who believed their
children had been harmed by MMR. Hardly an unbiased
study!
Think-Pair-Share
• In your group discuss the advantages
and disadvantages of vaccines
• Produce a rough table in your book of
your ideas
Advantages
Disadvantages
Vaccinations
Advantages
• Help control
infections
• Big outbreaks of
diseases can be
prevented if a large
number of
population is
vaccinated
Disadvantages
• Don’t always give
you long term
immunity/ cover all
strains
• Sometimes they can
cause a bad
reaction (Although
this is very rare)
“I am worried about having my child
vaccinated, I have heard there is a link
between vaccination and autism. I am
also worried he may have an allergic
reaction…” Mrs. B Smith
Your task… write a response to Mrs. Smiths letter, and
explain to her the pros and cons of having her child
vaccinated.
Extension: Explain why the number of cases of MMR
rose after 1985?
Antibiotics
Learning Objective:
To be able to explain how Antibiotics are used in the treatment of
infections
Lesson Outcomes
Vocabulary
Antibiotic
Could be able to explain why each
stage of the development of a new
medicine is needed.
Should be able to explain why
antibiotics cannot be used to
treat infections by pathogens
other than bacteria.
Must be able to explain why
antibiotics are useful for
treating bacterial infections
Skills being used in this lesson:
Listening
Presenting
Problem Solving
Creativity
Staying Positive
Aiming High
Leadership
Teamwork
Virtue linked to this lesson:
Good temper
Antiseptics
https://www.youtube.com/watch?v=Lk2v8BvIeTM
(35:00)
Alexander Fleming
https://www.youtube.com/watch?v=N2-7UQWrYPY
Fleming
Starter
What do the following key words do:
1. Antibacterial
2. Antiviral
3. Antifungal
4. Antibiotic
5. Antiseptic
Painkillers
• Medicines contain useful drugs.
• Often, medicines don’t affect the microbe
making you feel ill, they soothe the
symptoms.
– E.g. throat sweets,
– E.g. painkillers (aspirin, ibuprofen)
Medicines relieve symptoms but do not
kill pathogens!
• Some medicines do target the microbe…
Antibiotics
• Antibiotics damage bacteria and
eventually kill them e.g. penicillin
• Different antibiotics kill different types of
bacteria.
• Each type of antibiotic interferes with the
bacteria’s life processes, e.g making a cell
wall.
• They do not kill viruses, protozoa or fungi.
• However, they don’t affect human cells
Antibiotics have no effect on viruses
either.
Antiseptic
Antiseptics/Disinfectants
kill bacteria outside body
but are too poisonous to use
inside body.
Quick Review
What’s the difference between
painkillers and antibiotics?
Painkillers (e.g. aspirin) are drugs that relieve pain.
However, they don’t actually kill the pathogen, they just
help reduce the symptoms.
Antibiotics (e.g. penicillin, amoxicillin) actually kill (or
prevent the growth of) the bacteria causing the problem,
without killing your own body cells.
Different types of antibiotic kill different types of bacteria.
But, antibiotics don’t kill viruses!
Type of
medicine
Painkillers
Antibiotics
What do they do in
the body? (How do
they help you?)
Any problems?
Give some
examples
(Outside the body/ on inorganic objects such
as tables).
Antibiotic efficiency
Which one of
these antibiotics
is the most
effective?
How can you
tell?
Antibiotic efficiency
Antibiotics diffuse into the
agar and kill the bacteria
• Not all antibiotics
are effective
against every type
of bacteria.
• That is why it is
important to use a
specific antibiotic
for a specific type
of bacteria.
Investigating effectiveness
Agar plates covered with bacteria can be used to
test substances to see if they have antiseptic or
antibiotic properties. A paper disc can be soaked
in the test substance and placed on the agar. If
the substance kills bacteria, they won’t grow in
the area near paper discs or the holes.
Results
Independent variable:
plant extract
Garlic
Ethanol
Penicillin
Graph
Conclusion
Dependent variable: diameter of
area with no bacteria
Units measured in? mm
Test 1 Test 2 Test 3 Average
Antibiotic Resistance
Bella’s doctor
prescribed her
antibiotics for an
infected wound.
Just like us, the microbes
in Bella’s wound showed
a lot of variation.
The darkest ones were
hardest to kill.
When Bella took
antibiotics she felt better
straight away ...
... because most of the
bacteria died.
A day later the pus was
gone from
her wound.
After three days her wound
began to heal.
Most of the bacteria were
gone.
Taking more antibiotics
seemed pointless, so Bella
threw them away.
That was two weeks ago.
Bella is back in hospital and her leg
is worse than before ...
... but now the
antibiotic won’t help.
The genes that made one
microbe harder to kill have
been passed to all its offspring,
so they are resistant to the antibiotic.
Antibiotic Resistance
• If a bacteria cannot be
killed by a certain
antibiotic then we say
that it is resistant to
that type of antibiotic.
• For example, MRSA
stands for methicillin
resistant Staphylococcus
aureus and it is called
as such because it is
resistant to methicillin.
Resistance to Antibiotics
• Antibiotics discovered in 1940s – thought to be the
end of people dying from bacteria induced diseases
• But the bacteria started to become resistant to the
antibiotics
Exam-Style Question
Peer Assessment
In the population of bacteria, some bacteria
may have a mutation in their DNA which
makes them resistant to the antibiotic. The
antibiotic kills the normal bacteria, but the
bacteria with the mutation survive because
they are resistant.
Give your partner
a mark out of 3
Peer Assessment
mutate - sometimes the mutations cause them to be resistant
Bacteria can
to (not killed by) an antibiotic
.
2.
If you have an infection
, some of the bacteria might be resistant
to
antibiotics.
3.
This means that when you treat
the infection, only the non-resistant
strains of bacteria will be killed
.
4.
The individual resistant bacteria will survive
and reproduce
, and the
population of the resistant strain will increase
.
This is an example of
.
natural selection
infection
5.
This resistant strain could cause a serious
that can’t
be treated
by antibiotics. E.g. MRSA (methicillin-resistant Staphylococcus aureus) causes serious
wound infections and is resistant to the powerful antibiotic methicillin .
6.
To decrease
the rate of development of resistant strains, it is important for
doctors to avoid over-prescribing antibiotics. Therefore, you will only get them
for more serious illnesses and infections.
• Word Bank:
Resistant, increase, treat, survive, infection, methicillin, over-prescribing, mutate, infection,
decrease, antibiotic, can’t, killed, resistant, non-resistant, reproduce, natural selection, MRSA
1.
https://www.youtube.com/watch?v=tMPY-zf8X94
https://www.youtube.com/watch?v=znnp-Ivj2ek
Hospitals have introduced programmes to reduce MRSA infections in patients
because antibiotics have become less effective.
The graph shows the number of males infected with MRSA during their stay in
hospital.
A programme of intensive use of antiseptics in hospitals has been used since 2005.
Use the information given and your own scientific knowledge to explain the
trends shown in the graph.
(6)
Developing new drugs
Safety
Effectiveness
Dosage
This is important as some drugs are toxic, and have other side effects that
might be harmful to people.
This is also known as efficacy, and checks how well the drug cures the
disease, or improves symptoms.
This varies, and has to closely controlled, as too high a concentration might
be toxic.
Drug trial failure examples:
• Thalidomide past the drug trials at the time, but cause sever birth defects.
• Penicillin was not effective when tested on animals and almost never made it
to human trials.
• Zelmid an antidepressant that passed animal trials, but caused severe
neurological problems in humans.
• Flosint an arthritis drug that passed animal trials, but, caused deaths in
humans.
• Nomifensine another antidepressant, was linked to kidney and liver failure,
anaemia, and death in humans.
Developing new drugs
Three stages of testing drugs
There are three main stages of testing:
• Preclinical drug trials - The drugs are tested using computer models and
human cells grown in the laboratory. This allows the efficacy and possible
side effects to be tested. Many substances fail this test because they
damage cells or do not seem to work.
• Animal trials - Drugs that pass the first stage are tested on animals. In the
UK, new medicines have to undergo these tests. But it is illegal to test
cosmetics and tobacco products on animals. A typical test involves giving a
known amount of the substance to the animals, then monitoring them
carefully for any side-effects.
• Human clinical trials - Drugs that have passed animal tests are used in
clinical trials. They are tested on healthy volunteers to check that they are
safe. The substances are then tested on people with the illness to ensure
that they are safe and that they work. Low doses of the drug are used
initially, and if this is safe the dosage increases until the optimum dosage is
identified.
Developing new drugs
Developing new drugs
Title: Plant defences
Date:
LO
Describe how plants respond to pathogen infections.
SC
Silver - Describe some physical barriers of plants to pests and
pathogens.
Gold – Describe some chemical defences of plants to pests and
pathogens.
Platinum- Describe how plant protective chemicals are used to
treat human diseases or symptoms.
https://www.youtube.com/watch?v=HIll-_blL5c Ash die back (Chalara)
https://www.youtube.com/watch?v=Hja0SLs2kus Plant defences
https://www.youtube.com/watch?v=zVbponLWnK8 the very dead hungry caterpillar
Plant barriers to infection
Physical
Chemical
Hairs
Waxy cuticle
Epidermis
Guard cells
Bark
Thorns
Suberins
Toxins
Bitter tasting chemicals
Pungent smells
Wind, water, insects and chemotaxis
help pathogens reach their hosts
Once they reach their host they need to get inside
the plant to cause disease .. that’s not so easy.
Pathogens must
overcome formidable
plant defences: physical
and chemical barriers
Let’s start with the physical …
Waxes cover many plant surfaces providing
the first physical barrier to pathogen entry.
This Scanning Electron
Microscope (SEM)
image shows waxes
around the only ‘weak
spot’ in a leaf’s physical
barrier – the stomata.
Some pathogens head
specifically for this
opening.
The pathogen must gain entry through wax
layers, the plant cuticle and the cell wall.
Tough bark and/or thorns will deter a
herbivore
In some case, xylem vessels maybe blocked by
the formation of tyloses preventing pathogen
spread.
SEM of xylem vessels
Papillae (P) may form on the inner side of cell walls.
This structure can trap invading pathogens.
Papilla
Fungal Infection
Peg
Fungal spore
This SEM image of
powdery mildew
attacking barley, shows
a ‘failed’ papilla (red),
and the haustorium
(fungal feeding
structure) in a barley
cell.
Plants actively defend themselves
against pathogens
Plants resist pathogens
through active processes that
include recognition of the
pathogen and defence
responses to fight it
Inside the Plant the battle continues
Mint
Witch hazel
Chemical Barriers
Anti-microbial compounds inside roots
of oat
Many chemical reactions occur inside
plant cells in response to the invading
pathogen