This is in addition to your revision!

This is a big topicYou have been warned

Microorganisms are Very SmallBiggest Smallest

When millions of them grow in one place then you can see them

Colonies of Bacteria and Fungi growing in an agar plate.

Agar jelly is their food.

FUNGI VIRUSESBACTERIA

(On a needle)

Some microorganisms are PathogenicPathogenic means they cause diseases

• Athletes foot, Thrush Fungal• Smallpox , Flu Viral• Tuberculosis, Cholera Bacterial

If you are infected with one of these you will show symptoms:E.g. runny nose, high temp, spots, sneezing etc.

Some diseases are caused by the things we do: Over eating, cigarettes, alcohol, drugs

These are called LIFESTYLE diseases:Obesity, Heart disease, lung cancer.

Remember: YOU can change your lifestyle

How do bacteria Grow? Real Fast !!!

Rapid growth

Lots of food, water, warmth and space

Growth rate = death rate (running out of food or too much

excretory products)

More dying than growing

Just give them: WARMTH – FOOD – WATER (Not O2)

Getting used to their Petri dish food supply

1 cell – 2 – 4 – 8 – 16 – 32 – 64 – 128 – 256 – 512 - In just 3 Hrs

------------ And it looks like this -------------

Time

AntimicrobialsAny substance that inhibits (slows or stops) the growth of bacteria, fungi or bacteria,

Eg: antibiotics, vaccines, antiseptics

So why don’t we get ill all the time?

Skin, antiseptic tears, mucus in our nose and windpipe, stomach acid, hairs & earwax all stop them getting in to our body.

And if that doesn’t stop them – White Blood Cells from our

immune system will:

That’s me, the white one

Antibiotic Resistant Bacteria – Superbugs – MRSA

These are all the exactly the same thing, NASTY bacteria that cannot be killed by

Antibiotics

click for video

Final resistant population

Why are they so common?

People take AB’s for colds & flu People don’t finish the course

It’s just normal variation, natural selection & mutations

ALMOST FORGOT: Antibiotics don’t kill VIRUSES

The Immune System‘’ It’s me your friendly

neighbourhood white blood cell again. This is how we kill microbes’’

1. We find them, surround them and digest them, BURP! (phagocytosis)

2. Some of us make chemicals called antibodies that stick to microbes. Each microbe has antigens ( molecules on their surface). Antibodies recognise the shape of each different antigen & stick to them. Death follows

AND

Foreign blood cell being attacked

Arghhh

‘’OK, but what if I’m too sick and my immune system isn’t stopping them’’?

• If it’s a bacteria take a course of antibiotics – • And don’t stop just because you feel better• And you might experience side effects, even

death!!• And, they might kill all your good microbes.‘’SO WHAT, THE ONLY GOOD MICROBE IS A DEAD MICROBE’’

If a fungus is left it will have as much food, space and water as it wants. ‘’And what next’’?

GROWTH

-- Itch Itch Scratch Scratch --And this arrow is NOT pointing at your feet

Better get the bio yoghurt out

‘’Ahh, that’s better’’

‘’I’ve had chickenpox, why can’t I catch it again’’?

‘’Because your now immune to it silly’’How does that happen?

WBC make antibodies

Antibodies attach to nasty microbes & kill them

I think I’m dying!

Once killed, the WBC’s become MEMORY CELLS which remember the microbes antigens

1. First Infection

2. If there is a second similar Infection

Me again

Yeh and I remember

you ‘cos I’m a

memory cell Zap Bang

Wallop!The differences between 1 & 2 are:1. Antibodies are made slowly and you may feel ill before all the MO’s are all killed2. Antibodies are made really fast and you don’t get ill at all. You are IMMUNE

I’m dead!

This is what an Immune Response looks like

Antibody numbers

Second encounter with

pathogen

First encounter with pathogen

Memory cells become active Pathogen

rapidly destroyed

Memory cells created here

Vaccines & Vaccinations

• A vaccination make you immune from a disease

• A vaccine contains either:• A dead MO, parts of a MO, or a weakened MO

WHY?• They ALL contain the MO’s antigens/markers• They all lead to memory cells being made

Some Problem Microbes• Flu Virus – mutates rapidly (changes it’s antigens) • HIV virus – Attacks the immune system and also mutates rapidly…very NASTY

Original antigens New antigensMO MO

Testing Drugs• Drugs are tested for safety (side effects) and effectiveness (does it work?)• Testing involves 3 stages:• On human cells (relatively cheap & quick and may indicate how safe it is)• On animals (gives information on safety and effectiveness)• On people in a clinical trial (gives info on dosage, side effects)

Issues with Drug Tests

• Can take 10 years to get a new drug to market

• VERY expensive: staff & clinical trials, salaries,

looking after animals, hospital & lab costs, security

• Ethical issues with using live animals

• Ethical issues with testing it on humans,

especially if a placebo is involved.

• Must be approved & licensed by the government

Can you describe what's happening in the picture?When you have written your 5 descriptions, check

your answers on the next slide. No peeking!

1.

3

2

4

5. what about memory cells?

No Peeking until you have completed the first slide

1. Vaccine containing weakened,

dead pathogen or parts of it. Each of these has the pathogens antigens

(markers). All induce an immune response

2. Sometimes there are side

effects

5. Special White Blood Cells called memory cells are produced so when you come in contact with

the real pathogen they REMEMBER IT and produce antibodies SO FAST you don’t get sick; this is

immunity.

4. Antibodies attach to the pathogen’s antigens (markers). They neutralise the pathogen or attract phagocytotic WB Cells

3.White Blood cells produce antigens which match the pathogens antigens (markers)

Clinical or Human Trials

• Open label: Everyone knows who has the drug

• Blind: Only the doctors know who has the drug

• Double Blind: No one knows who has the drug

Increasingly more reliable results(less risk of bias)

Drug Safety• Taking any drug involves some risk & we all react

differently cos we are all genetically different• Side effects can be minor, severe or even cause death• Vaccinations have risks too, but the risk to the individual is

outweighed by the benefits to the rest of the population.

• If 95% of the public are vaccinated it stops a disease from spreading and can lead to its eradication (disappearance)

•Smallpox has been completely eradicated over the whole world

Why Do Arteries and Veins Look Different?

thin outer wall

thick layer of muscle and elastic fibres

thick outer layer

thin layer of muscle and elastic fibres

ARTERY

VEIN

Arteries carry blood at HIGH pressure, thick walls prevent them bursting, elastic fibres allow them to stretch and go back to their normal shape

Veins carry blood at LOW pressure so only thin walls are needed. They also have valves which prevent blood moving backwards

Capillaries, tiny blood vessels that carry oxygen & food to cells & remove carbon dioxide from cells

Running a Clinical Trial

• Trials have to be designed scientifically to be fair & reliable tests

• Participants put in to two groups

• Participants chosen randomly (increases reliability)

• One group gets the drug the other no drug, (the control group)

• A control group allows the groups/drugs effect to be compared

• If it’s a totally new drug the control group has a placebo

• A placebo looks exactly like the real drug but contains no drug

• Placebos raise ethical issues; if the new drug may cure a serious

disease and does work, people in the control group may die

The Circulatory System

• Veins carry blood into the heart

• Arteries carry blood away from the heart

• Coronary arteries supply heart cells with blood

• The heart is made of muscle cells.

• Every cell needs oxygen and glucose to make energy (respiration)

• The blood transports oxygen and glucose to every cell

• Blood leaves the heart under high pressure and returns under low pressure

An incubator has to control a babies temperature just like your body

This is the control system sequenceTemperature drops below 37oC Sensor detects drop & messages thermostat Thermostat messages heater to switch onTemperature rises to 37oC

Temperature rises above 37oCSensor detects the rise & messages thermostatThermostat messages heater to switch offTemperature dropsAnd the cycle continues

Thermostat Set at 37oC

Temperature sensor

Heater

37oC

A typical homeostasis graph

Bad Lifestyle = Increased Risk of a Heart Attack

• Risk factors: Smoking, lack of exercise, high salt/fat diet & family history

A heart attack animation

4. Cells now starved of oxygen

1. Bad lifestyle

2. Build up of fat in artery

5. Heart muscle cells begin to die

3. Blood flow is now reduced to the heart muscle cells

6. Heart attack takes place

heart attack - simple version

Water Control

Remember Water IN = Water OUT

IN: drinks, food, respirationOUT: Urine, faeces, breathing, sweating(exercise is dehydrating)

All of these effect the amount of water in the blood plasma and the kidney controls

it.

Homeostasis & Control Systems

• Your body needs to keep conditions inside your body the same - otherwise you will feel ill & be ill

THIS IS CALLED HOMEOSTASISREMEMBER IT!

• What needs to be kept under control?

• Levels of: glucose, water, salt, urea, CO2 & O2

• -Also: temperature, pH & blood pressure

• The underlined ones are in this syllabus

Control System Terms/Sequence

• Stimulus – A factor that changes (e.g. Temp rises)• Receptor (sensor) - Detects the change• Processing Centre – Decides the action to be

taken• Effector – Produces the response• Response - The change produced (e.g. Temp

drops)• Negative Feedback – Part of a control system that

reverses changes to bring them back to normal. Allows a quicker response & keeps the value closer to the normal value

• You should be able to recognise these in an incubator and in the kidney/water control system

ADH, the Kidney& Water Control

Stimulus

Stimulus

Detected by water receptors

in the processing

centre (brain)

PituitaryGland Effector (brings about the response)

Response: Less pee,

blood water increases

Response: More pee,

blood water decreases

Detected by water receptors in the processing

centre (brain)

PituitaryGland Effector (brings about the response)

Learn all the key words and understand how the flow chart works

Drugs and ADHLearn This

• Alcohol makes people pee a lot of dilute urine by lowering ADH production

• They become dehydrated

• Ecstasy does the opposite• Increases ADH production• Therefore, stops you peeing• So, ecstasy users should not drink too

much water, they will dilute their blood too much and pass out. OR WORSE!!

ANDDon’t forget to do as many past

papers as you can. Check your answers using the

mark schemes And if you’re aiming for an A* or B

go through each line of the syllabus/specification (find it on the OCR

web site)

Good Luck

Not Yet or not fully covered in this resource

• Epidemiological Studies (disease causes and their transmission)

• Correlations• The scientific method• Risks and benefits (to individuals and society)• Ethics

AND FINALLY, THE LAST SLIDE