Non - specific Defences Against Pathogens

Question 1

What are the 4 non specific defences to keep pathogens out

Answer 1

• skin
• inflammation response
• mucus/ mucous membranes
• expulsion reflexes

Question 2

What mechanisms does the skin use to keep pathogens out

Answer 2

• covers the body (physical barrier)
• has a flora of healthy microorganisms that outcompete pathogens for space on the body
• sebum, an oily substance that inhibits growth of pathogens

Question 3

What mechanisms does mucus and mucous membranes use to keep pathogens out

Answer 3

• mucous membranes secrete mucus
• covers the body tracts and airways
• traps micro organisms and contain coenzymes they destroy bacterial and fungi cell walls
• contains phagocytes, which remove remaining pathogens

Question 4

How do expulsion reflexes keep pathogens out

Answer 4

• coughs and sneezes - eject pathogen laden with mucus from gas exchange system
• vomiting and diarrhoea - expell gut contest and any infective pathogens

Question 5

How does blood clotting and wound repair keep out pathogens

Answer 5

Add in here!!!

Question 6

How does the inflammatory response keep out pathogens

Answer 6

Put answer here

Question 7

What are opsonins?

Answer 7

• Chemicals that bind to pathogens and ‘tag’ them so they can be more easily recognised by pathogens
• phagocytes have receptors on their cell surface membrane that bind to common opsonins, so the phagocyte can then engulf the pathogen.

Question 8

What are cytokines

Answer 8

• act as cell signalling molecules that inform other phagocytes that the body is under attack and stimulating them to move to the site of infection or inflammation
• they can also increase body temperature and stimulate the specific immune system

Question 9

What are the two key phagocytes that are involve3d in the innate non-specific secondary defences

Answer 9

Neutrophils

Macrophages

Question 10

What is a neutrophil

Answer 10

• 60% of all leukocytes (white blood cells)
• release large numbers during infection
• travel in blood, squeeze through capillary walls in the tissue
• short lived

Question 11

What are macrophages

Answer 11

• larger than neutrophils
• found in organs
• leave bone marrow as immature monocytes
• Monocytes develop into macrophages as they settle in organs
• Long lived

Question 12

Explain the 6 stages of phagocytosis

Answer 12

1 - the phagocyte is attracted by chemicals produced by the pathogen
2 - phagocyte recognises the pathogen as non-self and binds to it
3 - phagocyte engulfs the pathogen and engulfs it in a vacuole called a phagosome
4- the pagosome combines with a lysosome to make a phagolysosome
4 - in the phagolysosome enzymes break down the pathogen
5 - the digested pathogen absorbed by the phagocyte’s antigens combine with MHC in the cytoplasm
6- MHC/antigen complex is displayed on phagocyte membrane , making an antigen presenting cell.

Question 13

What are the physical defences plants have against pathogens

Answer 13

• lignin is added - makes a mechanical barrier to invasion that is thicker and stronger
• blocking sieve plates - callose blocks sieve plates into the phloem, sealing off the infected part and preventing the spread of pathogens
• callose in th plasmodesmata- callose is deposited in the pasmodesmata between infected cells and helping to prevent pathogens spreading

Question 14

What are the chemical defences plants have against pathogens

Answer 14

• insect repellants
• insecticides
• antibacterial compounds
• plant proteins that disrupt bacterial and fungal membranes
  - anti fungal compounds - chitinase - an enzyme that breaks down chitin in fungal cell walls
  - anti oomycetes - break polymers found in the walls of oomycetes
  - general toxins -some plants make chemicals tha can be broken sown from cyanide compounds when plant cell is attacked

Question 15

2 what are cytokines

Answer 15

• act as cell signalling molecules, that inform other phagocytes that the body is under attack and stimulating them to move to the site of infection or inflammation