10: Diseases and immunity

Question 1

Define pathogen

Answer 1

disease-causing organism

Question 2

Define Transmissible disease

Answer 2

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

Question 3

Define active immunity

Answer 3

defence against a pathogen by antibody production in the body

Question 4

What is a host?

Answer 4

organisms that harbour pathogens

Question 5

How can pathogen for a transmissible disease may be transmitted?

Answer 5

through

• direct contact - blood, body fluids or
• indirectly - contaminated surfaces or food, from animals, or from the air

Question 6

Defences against infection (3) + examples

Answer 6

1. Mechanical barrier - skin and nasal hair
2. Chemical barrier - mucus and stomach acid
3. Phagocytosis and antibody production by white blood cells - can be enhanced by vaccination

Question 7

Antibodies and antigens (4)

Answer 7

• White blood cells detect pathogen
• specific ANTIBODIES (produced by lymphocytes) bind to
• specific and complementary ANTIGEN (protein found on cell membrane of pathogens)
• antibody-antigen complex

Question 8

4 methods of controlling the spread of disease

Answer 8

• hygienic food preparation
• good personal hygiene
• waste disposal
• sewage removal and taking precautions to ensure it does not contaminate drinking water

Question 9

Autoimmune disease

What is it? Give one example.

Answer 9

A disease caused by the immune system targeting and destroying body cells (itself)

Type 1 diabetes - in pancreas - insulin cannot be produced = unable to regulate blood glucose levels

Question 10

Active immunity definition

long or short term immunity?

Answer 10

long-term defence against a pathogen by antibody production in the body

Question 11

How can active immunity be obtained? (2)

Answer 11

gained after

• an infection by a pathogen, or
• by vaccination

Question 12

How are memory cells produced?

Answer 12

After pathogen is killed, some LYMPHOCYTES REMAIN as MEMORY CELLS.
if same pathogen enters again - lymphocytes would recognise the antigen and be able to produce new antibodies quicker.

Question 13

Passive immunity
long or short term?
are memory cells produced?

Answer 13

SHORT-TERM defence against a pathogen by antibodies acquired from another individual, e.g. mother to infant

• no memory cells produced

Question 14

Explain why is it important for newborn babies to have antibodies. [3]

Answer 14

• provides (passive) immunity;
• protects against infection/disease/pathogen(s);
• immune system of babies not yet developed;
• any one function of antibodies;
• reference to disease(s) mother has had;

Question 15

Process of vaccination (3)

Answer 15

– harmless (dead/attenuated version) pathogen given which has antigens
– antigens trigger an immune response by lymphocytes which produce antibodies
– memory cells are produced that give long-term immunity

Question 16

What is the role of vaccination in controlling the spread of diseases ?

Answer 16

Vaccinations - give protection against specific disease, boost body’s defence against an infection.

Can be used to control the spread of disease by providing herd immunity.

Question 17

Lymphocytes respond to infection by making and releasing special protein molecules
called antibodies.
Describe how antibodies provide protection from diseases caused by viruses and
bacteria. [3]

Answer 17

- antibodies attach to antigens: 
prevent movement around the body, 
prevent entry into cells ;
stop division ;
combine with / neutralise, toxins ;

• clump, bacteria / viruses, together ;
• help phagocytes engulf virus / bacteria ;

Question 18

Explain what is meant by the term antibiotic [2]

Answer 18

Drug/ medicine that

kills/ stops the growth of bacteria/ microbes

Question 19

State 2 ways in which the structure of a bacterium differs from the structure of a virus. [2]

Answer 19

bacteria have: cell wall, cell membrane, cytoplasm, ribosome(s), flagellum

virus structure is simply genetic material (RNA or DNA) inside a protein coat

Question 20

Functions of antibodies (7)

Answer 20

• stop pathogens spreading in the body
• stop pathogens entering cels ;
• stop division/reproduction of pathogens ;
• neutralise toxins
• cause pathogens to clump/agglutinate
• immobilise bacteria
• make it easier for phagocytes to ingest pathogens.

Question 21

Some mothers bottle-feed their newborn babies with formula milk rather than breast-feed.
Describe 4 advantages of breast-feeding, other than providing antibodies. [4]

Answer 21

• it’s free
• sterile/ no risk of infection
• provides most suitable/balanced nutrients
• composition of breast milk changes to match development
• reduce risk of allergies
• no preparation/easily available