Defense mechanisms and phagocytosis

Question 1

What is a phagocyte?

Answer 1

a type of white blood cell, which carries out phagocytosis and destroys pathogens

Question 2

Why is phagocytosis a non-specific defence mechanism?

Answer 2

as the phagocyte has multiple different receptors that can detect different pathogens. It does NOT have a single receptor that is only complementary to one pathogen.

Question 3

Outline the process of phagocytosis

Answer 3

1. Phagocyte is attracted to chemicals (toxins) released by the pathogen
2. Phagocyte binds to chemicals on the surface of the pathogen
3. The phagocyte engulfs the pathogen to form a phagosome
4. lysosomes fuse to the phagosome, and release lysozymes (hydrologic enzymes) that hydrolyse the pathogen

Question 4

What are 4 types of cell that can be recognised by the immune system?

Answer 4

• abnormal cells
• cells from a different organism of the same species
• toxins
• pathogens

Question 5

How is the body able to recognise self-cells?

Answer 5

In a fetus;
- many lymphocytes in the blood
- collide almost exclusively with self cells, as there is no infection due to protection from the placenta
- any lymphocytes which have receptors that fit the shape of self cells will be destroyed or suppressed
- this leaves lymphocytes that can almost exclusively recognise non-self cells

Question 6

Describe the roles of lysosomes in phagocytosis

Answer 6

fuse to phagosome and release lysozymes that hydrolyse the pathogen