phagocytosis 5.2

If physical barriers fail, what is the next line of defence in an organism?

Phagocytosis

- What are the two types of white blood cells?

1) Phagocytes (including neutrophils and macrophages).

2) Lymphocytes (including T & B lymphocytes and Memory Cells)

- Why is phagocytosis necessary?

At the end of phagocytosis, phagocytes present antigens on their cell surface membrane. These foreign antigens are recognised by T-cells and initiate the specific immune response.

Process 8)

1)The phagocyte recognizes a foreign antigen on a pathogen.

2)There are many receptors binding points on the surface of phagocytes, which will attach to antigen.

3)The phagocyte changes shape to move around)The phagocyte surrounds the pathogen engulfing it.


4)The pathogen is encased in a vesicle. Known as a phagosome.


5)Lysosomes fuse with the vesicle
releasing digestive enzymes known as lysozymes into the vesicle., this lytic enzyme hydrolyses the pathogen


6)The pathogen is destroyed.


7)The phagocyte then places the pathogens antigens on its surface, becoming an antigen-presenting cell.

8)the soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte.

Lysosomes and the

Lysosomes contain lysozymes; hydrolytic
enzymes.

These enzymes are digestive enzymes that
break down the pathogen into smaller and
smaller molecules.

The soluble, useful products are absorbed
into the cytoplasm and used by the cell.