diseases and immunity - key terms

Question 1

Define pathogen

Answer 1

a disease-causing organism.

Question 2

Define transmissible disease

Answer 2

a disease in which the pathogen can be passed from one host to another.

Question 3

Define direct contract

Answer 3

the pathogen is passed directly from one host to another through blood, body fluids, semen, etc.

Question 4

Define indirect contract

Answer 4

the pathogen leaves the host and is carried in some way to another e.g., contaminated surfaces/food, from animals, from air

Question 5

Define examples of mechanical barries

Answer 5

-Nostrils contain hairs that help trap dust
-The skin has a thick outer layer of dead cells

Question 6

Define examples of chemical barriers

Answer 6

-Sticky mucus which can trap pathogens
-In the stomach, hydrochloric acid is secreted, which kills many of the bacteria in food

Question 7

Define cells

Answer 7

Pathogens that manage to get through all these defences are destroyed by white blood cells.

Question 8

Define antibody

Answer 8

proteins that bind to antigens, directly destroying or marking pathogens for destruction by phagocytes.

Question 9

Define active immunity

Answer 9

defence against a pathogen by antibody production in the body.

Question 10

Define passive immunity

Answer 10

short-term defences against a pathogen by antibodies acquired from another individual.

Question 11

Define diarrhoea

Answer 11

loss of watery faeces

Question 12

Define cholera/vibrio cholerae

Answer 12

Cholera is a disease caused by a bacterium transmitted in contaminated water.
The cholera bacterium produces a toxin that causes the secretion of chloride ions into the small intestine, causing lower osmotic water movement into the gut, causing diarrhoea, dehydration and loss of salts from the blood.