Infection & Response
C5 - Communicable Disease:
5.1 - Health & Disease:
Communicable diseases are cause by pathogens such as bacteria that can be passes from one person
to another e.g. flu. Non-communicable cannot be transmitted from one person to another e.g. heart
disease. Other factors like diet (diabetes), stress and life situations such as financial status.
5.2 - Pathogens & Disease:
Bacteria are single-celled organisms that are much smaller than animals cells and is used to make
food like cheese and yogurt. There is 1-2kg bacteria in their guts. Viruses are even smaller than
bacteria, have regular shape and cause disease in each organism.
Pathogens cause disease by bacteria rapidly dividing (binary fusion) and produce toxins that make
you ill. Viruses take over cells of your body and live and reproduce inside them, this damages and
destroys the cell. Common disease symptoms include feverish temperatures. Headaches and rashes.
Pathogens are spread through the air (bacteria, virus, fungus) and droplet infection is common in
humans. Also, direct contact in plant diseases and STD’s or dirty needles. Moreover, Animals can be
vectors and water as fungal spores are in water. Humans also eat undercooked food and drink
contaminated water.
• Bacteria are single celled organisms which reproduce rapidly in your body and produce
antitoxins.
• Viruses aren’t cells but invade your cells and replicate rapidly. The cell bursts when viruses
replicate too much.
5.3 - Growing Bacteria in the Lab:
To cultivate microorganisms they need gel containing nutrients (culture medium), they also need
oxygen and warmth. Agar gel is used. You must be careful to not contaminate the petri dish and
cause a mutation. In schools incubations can only go up to 25°C as bacteria at 37°C can harm
humans. In hospitals, they can go higher than 25°C.
• Gel containing nutrients (culture medium) which also has oxygen and warmth
• Inoculate the sterile agar with microorganisms.
• After, seal the petri dishes and keep them in an incubator.
• Store them upside down so no condensation falls onto agar surface.
, • To sterilise the inoculating loop heat it the let it cool and use it to get the bacteria.
5.4 - Preventing Bacterial Growth:
Bacterial growth is affected by temperature, nutrients, oxygen, and pH, changing these can affect
population growth. Bacteria growth = Bacteria growth at start x 2 to power of number of divisions.
E.g. mean division is 30 minutes and 8 hours. 1 x 2 to power of 16 as there was only 1 bacteria at the
start.
To prevent bacteria growth you can change temperature, use chemicals, or an antiseptic which is a
disinfectant which is safe to use on human skin. Antibiotics are chemicals that can be used inside our
bodies which kill bacteria and prevent them from growing. You can see growth by finding radius and
using pi x radius to power of 2.
5.5 - Preventing infections:
Ignaz Semmelweis discovered that women died from giving birth as doctors did not wash their hands
before delivering babies. After insisting on washing hands, less women died.
There are many ways of preventing the spread of communicable diseases. One being hygiene such
as washing hands, using disinfectants, keeping raw meat away, sneezing into a tissue, and cleaning
agricultural machinery.
If someone is infected they should isolate to prevent passing on pathogens to other. This is also true
for plants. Also, you can destroy or control vectors like aphids, houseflies, and rats.
Vaccination is where a dose of the pathogen is injected in a harmless or dead form. The white blood
cells produce antibodies and memory cells. If injected with the live pathogen the White blood cells
produce substantial amounts of antibodies very quickly. It does not protect plants.
5.6 -Viral Diseases:
Measles symptoms are fever, and a red skin rash. It is spread through inhalation of droplets from
coughs. It could lead to brain damage and blindness. Most children in the UK are vaccinated against
it and have good living conditions.
AIDS is contracted through sexual contact or exchange of body fluids. Initial symptom is a flu-like
illness which attacks the immune system. No cure for AIDS but there is an antiretroviral drug which
stops the virus replicating as quickly.
Tobacco mosaic virus is a plant pathogen that creates a mosaic pattern on the leaves as the virus
destroys the cells. This slows down photosynthesis which slows down the growth of the plant. This
reduces the yield of the crop. Good field hygiene and vector + pest control prevent its spread.
C5 - Communicable Disease:
5.1 - Health & Disease:
Communicable diseases are cause by pathogens such as bacteria that can be passes from one person
to another e.g. flu. Non-communicable cannot be transmitted from one person to another e.g. heart
disease. Other factors like diet (diabetes), stress and life situations such as financial status.
5.2 - Pathogens & Disease:
Bacteria are single-celled organisms that are much smaller than animals cells and is used to make
food like cheese and yogurt. There is 1-2kg bacteria in their guts. Viruses are even smaller than
bacteria, have regular shape and cause disease in each organism.
Pathogens cause disease by bacteria rapidly dividing (binary fusion) and produce toxins that make
you ill. Viruses take over cells of your body and live and reproduce inside them, this damages and
destroys the cell. Common disease symptoms include feverish temperatures. Headaches and rashes.
Pathogens are spread through the air (bacteria, virus, fungus) and droplet infection is common in
humans. Also, direct contact in plant diseases and STD’s or dirty needles. Moreover, Animals can be
vectors and water as fungal spores are in water. Humans also eat undercooked food and drink
contaminated water.
• Bacteria are single celled organisms which reproduce rapidly in your body and produce
antitoxins.
• Viruses aren’t cells but invade your cells and replicate rapidly. The cell bursts when viruses
replicate too much.
5.3 - Growing Bacteria in the Lab:
To cultivate microorganisms they need gel containing nutrients (culture medium), they also need
oxygen and warmth. Agar gel is used. You must be careful to not contaminate the petri dish and
cause a mutation. In schools incubations can only go up to 25°C as bacteria at 37°C can harm
humans. In hospitals, they can go higher than 25°C.
• Gel containing nutrients (culture medium) which also has oxygen and warmth
• Inoculate the sterile agar with microorganisms.
• After, seal the petri dishes and keep them in an incubator.
• Store them upside down so no condensation falls onto agar surface.
, • To sterilise the inoculating loop heat it the let it cool and use it to get the bacteria.
5.4 - Preventing Bacterial Growth:
Bacterial growth is affected by temperature, nutrients, oxygen, and pH, changing these can affect
population growth. Bacteria growth = Bacteria growth at start x 2 to power of number of divisions.
E.g. mean division is 30 minutes and 8 hours. 1 x 2 to power of 16 as there was only 1 bacteria at the
start.
To prevent bacteria growth you can change temperature, use chemicals, or an antiseptic which is a
disinfectant which is safe to use on human skin. Antibiotics are chemicals that can be used inside our
bodies which kill bacteria and prevent them from growing. You can see growth by finding radius and
using pi x radius to power of 2.
5.5 - Preventing infections:
Ignaz Semmelweis discovered that women died from giving birth as doctors did not wash their hands
before delivering babies. After insisting on washing hands, less women died.
There are many ways of preventing the spread of communicable diseases. One being hygiene such
as washing hands, using disinfectants, keeping raw meat away, sneezing into a tissue, and cleaning
agricultural machinery.
If someone is infected they should isolate to prevent passing on pathogens to other. This is also true
for plants. Also, you can destroy or control vectors like aphids, houseflies, and rats.
Vaccination is where a dose of the pathogen is injected in a harmless or dead form. The white blood
cells produce antibodies and memory cells. If injected with the live pathogen the White blood cells
produce substantial amounts of antibodies very quickly. It does not protect plants.
5.6 -Viral Diseases:
Measles symptoms are fever, and a red skin rash. It is spread through inhalation of droplets from
coughs. It could lead to brain damage and blindness. Most children in the UK are vaccinated against
it and have good living conditions.
AIDS is contracted through sexual contact or exchange of body fluids. Initial symptom is a flu-like
illness which attacks the immune system. No cure for AIDS but there is an antiretroviral drug which
stops the virus replicating as quickly.
Tobacco mosaic virus is a plant pathogen that creates a mosaic pattern on the leaves as the virus
destroys the cells. This slows down photosynthesis which slows down the growth of the plant. This
reduces the yield of the crop. Good field hygiene and vector + pest control prevent its spread.
