10 1 diseases and immunity

A pathogen is an organism that causes disease.

False. A transmissible disease is caused by a pathogen that can be passed from one host to another.

Pathogens can be transmitted directly by direct physical contact; this can involve the exchange of blood or other bodily fluids.

True. A pathogen can be transmitted indirectly via contact with contaminated surfaces, contaminated food, infected animals and infected droplets in the air.

Body defences against pathogens include:

True. Skin is a physical barrier to pathogens. If it is cut or grazed this provides an entrance method for pathogens.

Mucus is produced to trap pathogens. Trapped pathogens can then be removed from the airways by coughing, blowing the nose or swallowing.

Water can become contaminated with pathogens, which can infect people if the water is used to wash hands, for drinking or for cooking.

False. Good personal hygiene is necessary for the control of disease:

Methods for controlling the spread of disease include:

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.

Effective methods of hygienic food preparation incude:

Active immunity is a defence against a pathogen by antibody production in the body.

Active immunity can be induced by:

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.

The difference between an antigen and an antibody is:

Antibodies bind to antigens, leading to:

True. Specific antibodies have complementary shapes which fit specific antigens.

Vaccination introduces weakened pathogens or their antigens into the body in order to induce immunity.

True. Vaccination stimulates an immune response that results in active immunity.

The role of white blood cells in vaccination is:

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. 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.

Vaccination helps to control the spread of disease because:

Passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual.

Passive immunity can be gained as follows:

Breastfeeding provides passive immunity to infants when antibodies pass from mother to infant via breast milk.

False. Memory cells are not produced in passive immunity.

Cholera is a disease caused by a bacterium.

Cholera is transmitted in contaminated water.

False. Cholera bacteria secrete a toxin that causes secretion of chloride ions into the small intestine.

The toxin secreted by cholera bacteria causes:

The symptoms of a cholera infection are: