Define the term pathogen.
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Define the term pathogen.
A pathogen is an organism that causes disease.
True or False?
Transmissible diseases are not caused by pathogens.
False.
A transmissible disease is caused by a pathogen that can be passed from one host to another.
How are pathogens transmitted directly?
Pathogens can be transmitted directly by direct physical contact; this can involve the exchange of blood or other bodily fluids.
True or False?
A pathogen can be transmitted indirectly via contaminated surfaces, food, animals and air.
True.
A pathogen can be transmitted indirectly via contact with contaminated surfaces, contaminated food, infected animals and infected droplets in the air.
What are the body's defences against pathogens?
Body defences against pathogens include:
skin
hairs in the nose
mucus
stomach acid
white blood cells
True or False?
Skin is a physical barrier to pathogens.
True.
Skin is a physical barrier to pathogens. If it is cut or grazed this provides an entrance method for pathogens.
Why do the nose and lining of the trachea produce mucus?
Mucus is produced to trap pathogens. Trapped pathogens can then be removed from the airways by coughing, blowing the nose or swallowing.
Why is a clean water supply important for controlling the spread of disease?
Water can become contaminated with pathogens, which can infect people if the water is used to wash hands, for drinking or for cooking.
True or False?
Good personal hygiene is not necessary for the control of disease.
False.
Good personal hygiene is necessary for the control of disease:
washing removes pathogens from the skin
the use of tissues when sneezing or coughing, instead of hands, means pathogens can be disposed of within the tissue
What are three methods required for controlling the spread of disease?
Methods for controlling the spread of disease include:
a clean water supply
hygienic food preparation
good personal hygiene
waste disposal
sewage treatment
What is the importance of sewage treatment in controlling the spread of disease?
Raw sewage should be treated to remove solid waste and kill pathogens before it is released into the environment. This prevents people from coming into contact with the pathogens in sewage.
What are two effective methods of hygienic food preparation?
Effective methods of hygienic food preparation incude:
keeping food cold to prevent pathogens from growing/reproducing
washing hands before preparing food
cleaning food preparation surfaces, utensils and equipment before preparing food
cooking/heating food to the correct temperatures to kill pathogens
covering food to prevent contamination from flies, which carry pathogens
Define the term active immunity. (Extended Tier Only)
Active immunity is a defence against a pathogen by antibody production in the body.
How can active immunity be induced in the body? (Extended Tier Only)
Active immunity can be induced by:
infection with a pathogen
vaccination
What is an antigen? (Extended Tier Only)
Antigens are molecules on the surface of cells. Each pathogen has its own antigens on its surface; the antigens of each pathogen have a specific shape.
What is the difference between an antigen and an antibody? (Extended Tier Only)
The difference between an antigen and an antibody is:
an antigen is a molecule found on the surface of a cell
an antibody is a protein that binds to specific antigens
What is the role of antibodies in the immune response? (Extended Tier Only)
Antibodies bind to antigens, leading to:
the direct destruction of pathogens
the marking of pathogens for destruction by phagocytes
True or False?
Antibodies have specific shapes which are complementary to specific antigens. (Extended Tier Only)
True.
Specific antibodies have complementary shapes which fit specific antigens.
What is vaccination? (Extended Tier Only)
Vaccination introduces weakened pathogens or their antigens into the body in order to induce immunity.
True or False?
Vaccination stimulates an immune response in the body. (Extended Tier Only)
True.
Vaccination stimulates an immune response that results in active immunity.
What role do white blood cells play in vaccination? (Extended Tier Only)
The role of white blood cells in vaccination is:
lymphocytes respond to the vaccine by producing antibodies
memory cells are produced
How does vaccination lead to long-term immunity? (Extended Tier Only)
Vaccination leads to long-term immunity because it results in the production of memory cells. When someone is infected again by the same pathogen the memory cells quickly produce the correct antibodies.
True or False?
Vaccines control the spread of disease. (Extended Tier Only)
True.
Vaccinating a large proportion of a population reduces the likelihood that a pathogen will spread; this is because most people in the population will be immune.
How does vaccination help control the spread of disease? (Extended Tier Only)
Vaccination helps to control the spread of disease because:
vaccinated people cannot spread the disease
the disease cannot spread to vaccinated people
levels of disease will be low enough in a vaccinated population to protect those who cannot be vaccinated
Define the term passive immunity. (Extended Tier Only)
Passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual.
How can passive immunity be gained? (Extended Tier Only)
Passive immunity can be gained as follows:
breast milk
across the placenta during pregnancy
by injection
How does breastfeeding enable passive immunity in an infant? (Extended Tier Only)
Breastfeeding provides passive immunity to infants when antibodies pass from mother to infant via breast milk.
True or False?
Memory cells are produced in passive immunity. (Extended Tier Only)
False.
Memory cells are not produced in passive immunity.
What is cholera? (Extended Tier Only)
Cholera is a disease caused by a bacterium.
How is cholera transmitted? (Extended Tier Only)
Cholera is transmitted in contaminated water.
True or False?
Cholera bacteria secrete chloride ions into the intestine. (Extended Tier Only)
False.
Cholera bacteria secrete a toxin that causes secretion of chloride ions into the small intestine.
What effect do cholera bacterial toxins have on the small intestine? (Extended Tier Only)
The toxin secreted by cholera bacteria causes:
secretion of chloride ions into the intestine
an increased solute concentration in the intestine, due to the presence of chloride ions
movement of water into the gut by osmosis
diarrhoea, due to the increased water content of the intestine
What are the symptoms of a cholera infection? (Extended Tier Only)
The symptoms of a cholera infection are:
diarrhoea
dehydration