Defence Against Patnogens

Question 1

Animal Defences

Answer 1

1) The skin: acts as a physical barrier, Produces antimicrobal substances
2) Mucous membranes: protect body openings that r exposed to the environment, EG mouth, nose, ears. Mucus traps pathogens.
3) Blood clotting: mesh of protein fibres. Blood clots plug wounds to prevent pathogen entry and blood loss.

Formed when platelets are exposed to damaged blood vessels.

Question 2

Animal defences

Answer 2

4) Inflammation: EG, swelling, pain,redness,heat.
- Inflammation is triggered by tissue damage
- The damaged tissue releases molecules that make blood vessels more permeable, so they start to leak fluid
- Causing swelling
- vasodilation ( widening of blood vessels)- Increases blood flow, making the area hot, bringing white blood cells to the area to fight off any pathogens.

Question 3

Animal defences

Answer 3

5) wound repair- skin can repair itself after an injury.

Surface is repaired by the outer layer of a skin cells, dividing

Tissue below the wound contracts bringing the edges of the wound together.

6) Expulsive reflexes- attempt to expel foreign objects EG sneezing. HAPPENS automatically

Question 4

Plant defences

Answer 4

Physical plant defences:

• waxy cuticle acts as a physical barrier against pathogen entry
• callose is deposited by plants in

times of stress, callose makes it harder for pathogens to enter cells

Question 5

How might the spread of viruses be limited between cells

Answer 5

By callose deposition at the plasmodesmata

Question 6

Chemical plant defences

Answer 6

• Produce antimicrobal chemicals
• Which kill pathogens or inhibit growth

EG saponins are chemicals that destroy cell membranes.

EG IN PLANTS: plants produce chemicals called phytoalexins, which inhibit growth of other pathogens