10. Diseases and Immunity

Question 1

What is a pathogen?

Answer 1

a disease-causing organism

Question 2

What is a transmissible disease?

Answer 2

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

Question 3

What are the main ways a pathogen can be transmitted?

Answer 3

direct contact
by air
by animal vector
by food
by blood/other body fluids

Question 4

How can we categorize the main two ways a pathogen can be transmitted?

Answer 4

direct contact: including through blood and other body fluids
indirectly: including from contaminated surfaces, food, animals and air

Question 5

State 5 body defences.

Answer 5

• skin
• hairs in the nose
• mucus
• stomach acid
• white blood cells

Question 6

What are 5 methods to control the spreading of disease?

Answer 6

• clean water supply
• hygienic food preparation
• good personal hygiene
• waste disposal
• sewage treatment

Question 7

Define ‘active immunity’.

Answer 7

defence against a pathogen by antibody production in the body

Question 8

What are antigens? Where are they found?

Answer 8

they are substances that can induce the body to produce an immune response
found in pathogens, each has their own antigens

Question 9

What is the shape of antigens?

Answer 9

the shape varies, but each pathogen has its own antigens

Question 10

What are antibodies?

Answer 10

proteins produced by lymphocytes that will help destroy (mark for destruction by phagocytes) or directly destroy a pathogen

Question 11

What are two ways that antibodies function?

Answer 11

• directly destroy pathogens
• mark pathogens so phagocytes can destroy them

Question 12

What is something a specific antibody must have in order to destroy a specific pathogen?

Answer 12

a complementary shape to fit the specific antigens

Question 13

Define ‘active immunity’.

Answer 13

person exposed to pathogen
person’s own lymphocytes produce antibodies + memory cells

Question 14

What are two methods of active immunity?

Answer 14

• infection by pathogen
• vaccination

Question 15

Outline the process of vaccination.

Answer 15

1. weakened pathogens/antigens are put into the body
2. antigens stimulate an immune response from lymphocytes
3. lymphocytes produce antibodies to destroy pathogen
4. memory cells are produced, causing long-term immunity

Question 16

Explain the role of vaccination in controlling the
spread of diseases.

Answer 16

when everyone is vaccinated and protected from a pathogen, disease spread is much more controlled

Question 17

Define ‘passive immunity’.

Answer 17

a short-term defence from a pathogen acquiring antibodies from another source

Question 18

What are two examples of passive immunity?

Answer 18

• across placenta
• breast milk

Question 19

What is an advantage of passive immunity?

Answer 19

protection occurs immediately

Question 20

What are two disadvantages of passive immunity?

Answer 20

protection is short-term
memory cells are not produced

Question 21

Why is breast-feeding important?

Answer 21

passive immunity is developed in infants and help babies be protected until they can take their first vaccines

Question 22

Describe the antibody response stages after vaccination.

Answer 22

1. person is vaccinated
2. primary immune response: slow production of antibodies by lymphocytes
3. primary production of memory cells
4. secondary immune response: person infected again, faster and stronger production of antibodies by memory cells
5. secondary production of memory cells: store antigen memory for longer

Question 23

What is cholera?

Answer 23

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

Question 24

What are symptoms of cholera?

Answer 24

diarrhoea
dehydration
vomiting
(loss of ions from blood)

Question 25

What does the cholera bacterium do?

Answer 25

produces a toxin which secretes chloride ions into small intestine
causes osmotic movement of water into the gut

Question 26

What is a vector?

Answer 26

an organism that transmits a pathogen from an infected to a non-infected person

Question 27

What are direct methods of transmission?

Answer 27

exchange of blood and body fluids

Question 28

What are indirect methods of transmission?

Answer 28

by air
by food/drink
by animal vector
by touching contaminated substances/surfaces/food

Question 29

What are the two types of barrier in the first line of defence?

Answer 29

mechanical barriers and chemical barriers

Question 30

What does the first line of defence do?

Answer 30

prevent pathogens getting into the body or damaging its surfaces

Question 31

What does the second line of defence do?

Answer 31

detects and destroys pathogens, once pathogen gains entry to the body

Question 32

What do mechanical barriers do?

Answer 32

block pathogens from entering the body

Question 33

What do chemical barriers do?

Answer 33

substances that trap or kill pathogens

Question 34

Examples mechanical barriers

Answer 34

• skin
• hairs in the nose

Question 35

Examples chemical barriers

Answer 35

• mucus
• stomach acid

Question 36

What are memory cells?

Answer 36

• cell formed from a lymphocyte as the immune system responds to an infection
• remains in bloodstream + can recognise pathogens that infect after a first infection
• then differentiates to form antibody-producing lymphocytes that mount a secondary response