Defences

Question 1

Examples of Human primary defences include …

Answer 1

The skin acts as a barrier
Blood clotting and skin repair
Mucous membranes
Coughing and sneezing
inflammation

Question 2

Examples of Plant passive defences include …

Answer 2

Cellulose barrier 
Lignin 
Waxy cuticle
Bark 
Callose blocking flow in sieve tubes

Question 3

Examples of Plant active defences include …

Answer 3

Deposit callose
Close stomata 
Add cellulose 
Induce cell necrosis 
Increase the number of oxidative bursts
Produce chemical defences

Question 4

Plant chemical defences - use of phenols

Answer 4

Antibiotic and antifungal proteins. One example is the tannins present in tree bark

Question 5

Plant chemical defences - use of Alkaloids

Answer 5

Compounds containing nitrogen (e.g. caffeine, nicotine, cocaine and morphine) are bitter to stop herbivores feeding on them and affect enzyme action

Question 6

Plant chemical defences - use of defensins

Answer 6

These cysteine-rich, defensive proteins have anti-microbial activity. They appear to affect the functioning of ion transport channels in the plasma membrane.

Question 7

Plant chemical defences - use of hydrolytic

enzymes

Answer 7

Present in the spaces between cells
Eg. Chitinases break down the chitin in fungal cell walls,
glucanases hydrolyse the glycosidic bonds in glucans,
lysozymes destroy bacterial cell walls.