Immune System

Question 1

Name the 5 chemical/ physical barriers to keep pathogens out

Answer 1

1. skin
2. Mucous membrane
3. Lysozyme
4. Stomach acid
5. Gut flora

Question 2

Describe the skin as a barrier

Answer 2

1. Outer layer of dead cells (in epidermis) contain tough protein keratin
2. Skin flora outcompeted for nutrients
3. Cut skin is quickly sealed by blood clotting

Question 3

Describe the mucous membrane as a barrier

Answer 3

Openings in the skin lined with mucous membrane to keep moist. Mucous and cilla reduce risk of infection

Question 4

Deceive lysosome as a barrier

Answer 4

1. Secretions in eyes and mouth contain this enzyme

2. Hydrolysis’s peptidoglycan cell wall of bacteria

Question 5

Describe stomach acid as a barrier

Answer 5

pH of about 2 which kills most pathogens

Question 6

Describe gut flora as a barrier

Answer 6

1. Aid digestion

2. Outcompete pathogenic bacteria

Question 7

Describe the structure of a virus

Answer 7

Protein coat called capsid

Question 8

Define a pathogen

Answer 8

Any organism that causes disease

Question 9

What are the 4 mains routes a pathogen can enter the body

Answer 9

1. Cuts in skin
2. Digestive system (in food)
3. Respiratory system (inhaled)
4. Mucosal surfaces

Question 10

What are the body’s 2 types of immune response

Answer 10

1. Non specific

2. Specific

Question 11

What are 3 characteristics of a non-specific immune response

Answer 11

1) a response effective against a wide range of pathogens
2) no recognition of pathogens
3) no reaction to specific antigens

Question 12

Define an antigen

Answer 12

1) they are a molecule that are recognised as foreign that activate cells in the immune system
2) found on surface of cell
3) proteins or polysaccharide

Question 13

Describe inflation

Answer 13

1) damaged WBC and mast cells release histamine
2) this causes arterioles to dilate, increasing blood flow to damaged area
3) also increases permeability of capillary walls, so more immune cells leak
4) increases sensitivity of nerve endings

Question 14

How does inflammation help defend against pathogens

Answer 14

1) plasma carrying antibodies and WBCs leak out of capillaries
2) these can now attach pathogens

Question 15

Explain the 4 characteristics of inflammation

Answer 15

1) redness: increases blood flow
2) painful: increases sensitivity of nerves
3) swelling: oedema (excess tissue fluid)
4: hot to touch: increased metabolic activity

Question 16

Describe lysozyme action in non-specific response

Answer 16

Hydrolysis of peptidoglycan bacteria cell wall

Question 17

Describe interferon

Answer 17

1) provides non-specific defence against viruses
2) viral infected cells produce interferon
3) diffuses to surrounding cells
4) inhibits viral protein synthesis

Question 18

Define phagocytosis

Answer 18

Engulfment of pathogens

Question 19

Define a phagocyte (e.g macrophage)

Answer 19

Type of WBC that carries out phagocytosis

Question 20

Describe how phagocytosis works

Answer 20

1) phagocyte recognises antigen on pathogen
2) engulfs pathogen
3) lysosome bonds with phagosome, releasing digestive enzymes
4) phagocyte then presents pathogens antigens in surface to active other immune cells
5) now and APC

Question 21

Name 2 digestive enzymes in lysosome action

Answer 21

1. Lysozyme

2. Protease

Question 22

Explain how macrophages present antigens to T helper cells

Answer 22

CD4 receptor on T helper cell bonds to MHC on macrophage

Question 23

What is MHC

Answer 23

Major histocompatibility complex (binding receptor on phagocyte)