Cells part 2

Question 1

How does the skin act as a defence in the body

Answer 1

• acts as a protective barrier to pathogens. dead skin cells layer stops pathogens from piercing through
• oily sebum covers the skin. creates a slightly acidic layer that prevents growth of harmful bacteria
• harmless micros on skin surface, compete with pathogens for resources prevents their growth

Question 2

How are the breathing and digestive systems adapted to act as a defence ?

Answer 2

• lined with a mucous membrane which secretes mucous and traps microorganisms
• can then be destroyed by WBC called phagocytes
• mucus also contains lysozyme which destroys bacteria by breaking down cell wall ( also found in tears)

Question 3

How is the stomach adapted for defence against pathogens ?

Answer 3

• mucus in stomach contains hydrochloric acid, helps to kill pathogens in food or water

Question 4

What are expulsive reflexes ?

Answer 4

body tries to expel pathogen that has entered body ie through sneezing, coughing, blowing nose, vomiting etc

Question 5

What are the two main types of phagocytes ?

Answer 5

macrophages and neutrophils

Question 6

What are antigens

Answer 6

chemicals on the surface of cells which allow us to recognise them. foreign antigens are found on pathogens., so the body wouldn’t recognize these, and thus go for attack.

Question 7

What are opsonins ?

Answer 7

special molecules which recognise the foreign chemicals and stick to them. tag pathogen as foreign

Question 8

What are neutrophils

Answer 8

• phagocyte and granulocyte. involved in allergy response - release histamine

Question 9

What are macrophages

Answer 9

phagocytes and antigen-presenting cells which are derived from monocytes. Long-lived immune cells

Question 10

What is a granulocyte?

Answer 10

type of WBC which contains protein granules

Question 11

Phagocytes act as what

Answer 11

non specific defence in body

Question 12

Lymphocytes act as what

Answer 12

specific defence because they release antibodies and antitoxins which are complement to antigens found on pathogen surface

Question 13

Describe the role of phagocytes ( neutrophil) in breaking down pathogen

Answer 13

• phagocytes such as neutrophils attracted to molecules produced by pathogens. moves towards pathogen
• receptors on membrane attach to opsonins, phagocytes engulfs pathogen. pathogens now engulfed into phagosome
• lysosomes move towards phagosome and fuse with it to form lysophagosome.-
• lysosomal enzymes now break down the pathogen and destroy it.