10. Disease and immunity

Question 1

Describe a pathogen

Answer 1

A disease-causing organism

Question 2

Describe a transmissible disease

Answer 2

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

Question 3

how is a pathogen transmitted

Answer 3

(a) direct contact- through blood contact, breast feeding, blood transfusion, sharing needles, sexual contact

(b) indirectly- from contaminated surfaces, food, animals and air

Question 4

Describe the body defences,

Answer 4

P barrier- skin, hairs in the nose, mucus

C barrier- stomach acid and white blood cells

Question 5

Importance of controlling the spread of disease

Answer 5

(a) a clean water supply
(b) hygienic food preparation
(c) good personal hygiene
(d) waste disposal
(e) sewage treatment

Question 6

Describe and state differences between Active and Passive immunity

Answer 6

A long-term defence against a pathogen by antibody production in the body. (gained after an infection by a pathogen or by vaccination).

a short-term defence against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk.

antibody produced- acquired
memory cell produced- not produced
long-term immunity- ST immunity
delayed response- immediate response

Question 7

Describe antibodies

Answer 7

proteins that bind to antigens leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes.

Question 8

Vaccination and lock and key mechanism

Answer 8

each pathogen has its own antigens,
which have specific shapes

specific antibodies have
complementary shapes which fit specific antigens

(a) weakened pathogens or their antigens are put into the body
(b) the antigens stimulate an immune response by lymphocytes which produce antibodies
(c) memory cells are produced that give long-term immunity

Question 9

Process of phagocytosis

Answer 9

A phagocyte moves towards a group of bacteria, and flows around them.

the phagocyte’s cell membrane fuses together, enclosing the bacteria in a vacuole

Enzymes are secreted into the vacuole and digest the bacteria

Soluble substances diffuse from the vacuole into the phagocytes cytoplasm

Question 10

Describe cholera and its consequences

Answer 10

a disease caused by a bacterium which is transmitted in contaminated water.

It produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of ions from the blood.