Single-celled living organisms
Very small cells - (1/100th the size of body cells)
Can reproduce very rapidly inside your body
Make you fell ill by:
- damaging your cells
- producing toxins (poisons)
Some cause disease
But some are harmless and useful. E.g:
- make food (yogurt and cheese)
- to treat sewage
- to make medicines
Are not cells
Tiny - 1/100 the size of bacterium
Replicate by invading your cells and using the cells' machinery to produce many copies of themselves.
The cells will usually then burst, releasing all the new viruses
The cell damage is what makes you feel ill
Usually have regular shapes
Can cause disease in every type of living organism from people to bacteria.
Defense Mechanisms - Skin
Covers the body and acts as a barrier
Prevents pathogens reaching the tissues beneath
Which can become infected.
Defense Mechanisms - Blood Clots
If you cut your skin you bleed,
Your blood quickly forms a clot.
The clot drys to become a scab.
The scab forms a seal over the cut, stopping pathogens from getting in through the wound.
Defense Mechanisms - Breathing System
You draw in air full of pathogens inside your body everytime you breathe.
You produce a sticky liquid, called mucus.
Mucus covers the lining of your lungs and tubes
It traps pathogens.
The mucus is then moved out of your body or swollowed down into your gut.
Then the acid in your stomach destroys the microorganisms.
The stomach acid destroys the microorganisms.
The stomach acid destroys most of the pathogens you take in through your mouth.
White Blood Cells
1. Ingesting Microbes
Can engulf foreign cells or pathogens and idgest/destroy them so they cannot make you feel ill.
2. Producing Antitoxins
Antitoxins counteract the toxins released by invading bacteria
White Blood Cells (2)
3. Producing Antibodies
Every invading cells has unique proteins (called antigens) on it's surface.
Whne your white blood cells come across a foreign antigen they will start to produce proteins called antibodies.
The antibodies lock onto and kill the invading cells.
The antibodies produced are specific to that type of antigen.
Antibodies are then produced rapidly and carried around the body to kill all similar bacteria or viruses.
If a person is infected with the same pathogen again the white blood cell will rapidly produce the antibodies to kill it.
The person is naturally immune to that pathogen and will not get ill.
Antibiotic Resistant Bacteria
Bacteria can mutate.
Sometimes the mutations cause them to be resistant to an antibiotic.
If you have an infection, some of the bacteria might be restistant to antibiotics.
So when you treat the infection, only the non-resistant strains of the bacteria will be killed.
The individual resistant bacteria will survive and reproduce - the population of the strain will increase, example of natral selection.
The resistant strain could cause a serious infection - can't be treated with antibiotics
E.g. MRSA resistant to the antibiotic methicillin.
To slow down the rate of development of resistant strains: doctors should avoid over-prescribing antibiotics.
Advantages of Vaccination
1. They have helped control lots of infectious diseases that were once common in the UK (e.g polio, measles , whooping cough, rubella, mumps, tetanus etc.)
Small pox no longer occuers at all, polio has fallen by 99%
2. Big outbreaks of disease (epidemics) can be prevented if a large percentage of the poulation is vaccinated.
So even people who are not vaccinated are unlikely to catch the disease
There are fewer people able to pass it on.
If a significant number of peopole aren't vaccinated, the disease can spread quickly and lots of people will be ill at the same time.
Disadvantages of Vaccination
1. Vaccines don't always work - they dont give you immunity
2. You can have a bad reaction to a vaccine - but they are very rare.
Swelling, fever, seizures
When you are first infected with a new microorganisms, it takes your white blood cells a few days to learn how to produce the right antibodies
By the time they produce the right antibodies you can become prety ill.
For a vaccination you inject a small amount of dead or inactive microoganisms.
They carry antigens which stimualte the white blood cells to produce the anitbodies to attack them
Even though the microorganisms are harmless
If the live microorganisms of the same type appear after that, the white blood cells can rapidly mass-produce antibodies to kill off the pathogens so quckily you won't even feel ill.
Some vaccinations "wear off" after time so booster injections are needed to increase levels of antbodies again.
MMR Vaccine - protects viruses that cause measles, mumps and rubella.
Drugs - Painkillers
Drugs that relieve pain
They don't actually cure the disease
They just relieve symptoms.
Other drugs do the same thing - reduce the symptoms without tackeling the cause
Cold remedies don't actually cure the colds
You can test the action of antibiotics or disinfectants by grwoing cultures of micoorganisms