Slides in this set
1. Microorganisms and disease
· Microorganisms: Microorganisms are things like bacteria, viruses and some fungi which
cannot be seen by the naked eye.
· Pathogens: Pathogens are microorganisms that cause disease and illness.
· White Blood Cells: These are highly specialised cells which fight pathogenic MOs by engulfing
them or producing antibodies (which will be further explained).
Symptoms of an illness can be caused by cell damage or toxins. Effects on the body such as a fever
(raised body temperature) and rash are known as symptoms. Different MOs cause different
symptoms to be shown. However, they all harm the body in some way and this damage is done to
the body's cells. A few MOs harm cells directly and some harm cells indirectly. For example
malaria parasites invade red blood cells and multiply inside them which eventually makes the cell
burst open. This causes flu-like symptoms. Most infectious MOs release toxins which damage
cells. Some bacteria produce proteins which damage the material that holds cells together which
helps them invade the body more deeply. Viruses and the smallest MO, bacteria are in the middle
and fungi are the largest. Other MOs produce toxins which poison cells causing fever or
inflammation which is painful swelling. The reason why we have a fever because enzymes in the
MOs work at an optimum temperature which is near our own (37°C). Our body temperature rises
in order to denature the enzymes. MOs reproduce quickly in the human body because there are
the right conditions for them to live in (moist and warm = intestines). Bacteria reproduce by
simply dividing and viruses use parts of other cells to reproduce. Our body has the right
conditions for the chemical reactions in MOs to take place.…read more
You can work out the growth of an MO population in the following way:
Revisium Biologicus is a bacterium that reproduces once every 20 minutes at 38°C. If 10 R.
Biologicus bacteria are left to reproduce for 2 hours. How may bacteria will there be?
Step 1: Convert the time to minutes
2 hours = 120 minutes
Step 2: Divide the time by the time to get the amount of reproduction periods
120 ÷ 20 = 6 reproduction periods
Step 3: Multiply the original amount by 2 in order to get the amount of bacteria after the 1st
10 × 2 = 20 = 1st reproduction period
Step 4: Continue to do this until you have the amount for the sixth and final reproduction period
20 × 2 = 40 = 2nd reproduction period
40 × 2 = 80 = 3rd reproduction period
80 × 2 = 160 = 4th reproduction period
160 × 2 = 320 = 5th reproduction period
320 × 2 = 640 = 6th reproduction period
Answer: 640 Revisium Biologicus Bacteria…read more
2. The Immune system
· Antigens: These are substances that trigger immune responses. They are usually proteins on
the surface of a MO.
· Antibodies: These recognise foreign MOs. They are released by some WBC.
· Passive immunity: These are external safety precautions including tears and sweat making sure
that MOs do not enter the body.
· Active immunity: These are internal safety precautions which includes white blood cells and
antibodies these neutralise any foreign bodies that enter the body.
The role of the immune system is to fight off any invading microbes and deal with any infectious
MO. Immune responses always involves WBC. There are two types of WBC one type is called
phagocytes and they ingest or engulf MO. The second are called lymphocytes and they produce
antibodies. Phagocytes have a very flexible membrane so they can travel quickly around the body
and lymphocytes have a large nucleus in order to produce the genetic material for antibodies.
WBC have receptors that recognise particular antigens. Antibodies latch on to invading MOs and
do one of three things:  They mark the MO so other WBC can engulf and digest it.  They bind
to and neutralise viruses or toxins  Some can attach to bacteria and kill them directly. Once the
right WBC recognises an antigen it can divide to make more identical cells. Some WBC stay around
in the blood afterwards which are called memory cells. Memory cells can reproduce very quickly if
the same antigen enters the body for a second time. They produce loads of antibodies and kill off
the MOs before you become ill- this is known as immunity. This is how a virus invades the body: A
virus enters the blood stream and wants to get into a cell. It approaches the nucleus and uses its
genetic information to reproduce. The cell burst because it's replicated too much. The virus then
moves into neighbouring cells and invades the body. This makes a person ill.…read more
· Vaccinations: Vaccinations use a safe version of a dangerous MO. They help your immune
system fight disease.
· Epidemics: Big outbreaks of disease.
When your are infected with a new MO it takes your WBC a few days to get their numbers up and
produce the right antibodies to help them fight it. Immunisation through vaccinations involves
injecting dead or inactive MO which still carry the same antigens. This means that that your body
produces antibodies to attack them even though it is harmless. The body also produces memory
cells which will recognise the antigen of the MO should it appear again. The body then has the blue
print of the pathogen. This process means your body can fight the disease before you get sick.
Epidemics can be prevented by vaccinating the majority of the population because even those who
have not been vaccinated will not get it. This is because there are less people to pass it on to.
Vaccines and drugs have different effects on different people. This can be due to genetic
differences. Vaccines and drugs can never be completely safe for everyone because everyone is
different. 1 in 4 children who have the meningitis vaccine develop a painful swelling at the site of
the injection. Vaccinations in early childhood can offer protection against many serious diseases.
Sometimes more than one vaccine is given at once such as the MMR vaccine (measles, mumps and
rubella). Sometimes boosters are needed because the immune response to `memory' weakens.
Vaccines for viral diseases such as colds need to be researched and recreated every year as the
strain mutates. Edward Jenner invented vaccines. He noticed that milkmaids never got small pox
because they recovered from cow pox. He squeezed the pus from cow pox buboes onto a small
boy. The boy never got small pox. Cow pox is a very mild disease and small pox was a fatal disease.
Many people think this method was unethical because Jenner didn't obtain parental consent and
the boy could have died.…read more
· Antimicrobials: Antimicrobials can inhibit or kill bacteria, fungi and viruses.
· Superbugs: These are MOs that are resistant to most known antimicrobials.
Antimicrobials are chemicals that inhibit the growth or kill MOs without seriously damaging your
own body. Antibiotics are a type of antimicrobial that acts on bacteria. Antibiotics don't kill viruses
or fungi. Antibiotics were discovered by Alexander Fleming by accident. Was growing some
bacteria in a petri dish when a naturally occurring penicillin started growing in it also. The bacteria
didn't grow around the penicillin. MO can evolve and become resistant to antimicrobials. This is
due to random mutations in their DNA which leads to a change in their characteristics. This ability
to resist and antimicrobial is a huge advantage for the MO. It is better able to survive. The resistant
allele is then passed on to the offspring meaning future generations have this resistance. It then
spreads and becomes more common in a population of MO. Sometimes drug companies can come
up with more effective antimicrobials but it is just a matter of time before it becomes useless. The
more often antibiotics are used the greater the problem of antibiotic resistance becomes.
Antibiotics do not cause resistance but they create a situation in which naturally resistant bacteria
have an advantage and increase in numbers. If antibiotics are not helping you recover it is
pointless to take them and cause problems for everyone else. Lots of people stop taking their
antibiotics when they feel better but this can increase the risk of antibiotic bacteria emerging. This
is why you should always finish your course of antibiotics as prescribed by your doctor.…read more