Specific Immune Cells And Proteins

Question 1

What is the immune system composed of?

Answer 1

A range of white blood cells, lymph and tissue fluid.

Question 2

What is a phagocyte?

Answer 2

It is a cell which kills pathogens through phagocytosis, making them an antigen presenting cell.

Question 3

Describe the steps involved in phagocytosis

Answer 3

Engulf:
- phagocyte moves towards pathogen up the toxin concentration gradient.
- extends the cell membrane and cytoplasm around the pathogen to engulf it.
- contains pathogen inside a membrane bound phagosome.
Digest:
- lysosome fuses with the phagosome, forming a phagolysosome.
- releases lysozymes which hydrolyses pathogen proteins/antigens.
- forms small antigen fragments.
Display:
- vesicles containing antigen fragments moves to cell membrane.
- antigen fragments are displayed on proteins on cell surface/membrane.
- antigen presenting cell is formed.

Question 4

What is a lymphocyte?

Answer 4

• includes T cells and B cells
• formed from stem cells in bone marrow
• B cells develop in bone marrow but T cells mature in the thymus gland.

Question 5

What is specific about a T lymphocyte?

Answer 5

Have specific receptor proteins on surface.
—> which have a specific tertiary structure, so the shape of the binding site is specific and only complementary antigens can bind.

Question 6

What is specific about a B lymphocyte?

Answer 6

Have antibodies on their surface
—> which have a specific tertiary structure, so the shape of the binding site is specific and only complementary antigens can bind and firm antibody / antigen complexes.

Question 7

What are the different types of T cells?

Answer 7

1. Helper T cells (TH cells)
   —> these coordinate an immune response
2. Cytotoxic T cells (TC cells)
   —> these kill cells

Question 8

What are the different types of B cells?

Answer 8

• Plasma cells which make and release antibodies.
• Memory B cells which remain after the primary immune response.

Question 9

What is an antibody?

Answer 9

Proteins with a quaternary structure which is specific to one antigen.

Question 10

Where can antibodies be found?

Answer 10

1. In the surface membrane of B cells
2. In body fluids
   —> eg. Blood, tissue fluid, breast milk

Question 11

Describe the structure and function of an antibody.

Answer 11

• made up of 4 polypeptide chains to form a Y shaped molecule
• has 2 binding sites that are complementary to 1 specific antigen
  —> the binding sites have a unique primary structure that folds to give a unique tertiary structure that gives a unique shape which only one antigen can fit into.
  —> forming antigen-antibody complexes

Question 12

What is agglutination?

Answer 12

The antibodies form antigen-antibody complexes with the antigens which prevents them from moving.
—> this causes clumps of pathogens to form which can then be engulfed by phagocytes during phagocytosis.