3.2.5 The Defensive Functions of Mammalian Blood Flashcards Preview

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Flashcards in 3.2.5 The Defensive Functions of Mammalian Blood Deck (55)
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1

 What is an antigen?

Molecules (usually proteins) that stimulates an immune response when detected by body

2

Describe how lymphocytes recognise self from non-self

  1. Each lymphocyte recognises a different chemical shape
  2. They collide with body’s own material (self)
  3. Some lymphocytes have receptors that fit body’s cells
    1. These either die or are suppressed
    2. Remaining fit only foreign material

3

Name the 4 main stages of immune response

  1. Phagocytosis
  2. Phagocytes Activate T-cells
  3. T-cells Activate B-cells, which divide into Plasma cells
  4. Plasma cells make more Antibodies to a Specific Antigen

4

Where are phagocytes found?

In blood and tissues

5

Describe phagocytosis (5)

  1. Phagocyte recognises (foreign) antigen
  2. Phagocyte engulfs pathogen
  3. Enclosed in vacuole/phagosome
  4. (Vacuole) fuses with lysosome
  5. Lysosome contains enzymes (lysozymes) that hydrolyse pathogen

6

Why does phagocytes moves towards pathogens?

∵ they're attracted to pathogen's chemical products

7

Phagocytes engulf pathogens by _____

endocytosis

8

Waste products removed by _____

exocytosis

9

How do lysozymes break down bacteria?

Hydrolyse the cell walls of bacteria

10

What do phagocytes do at the end of phagocytosis?

Phagocyte presents pathogen's antigens on its surface to activate other immune system cells

11

What do T-cells only respond to?

Antigen-presenting cells

12

Where do T-cells (aka T-lymphocyte) mature?

In thymus gland 

13

Describe what T-cells do

  1. Respond to antigens on foreign and infected cells
  2. Specific receptors on helper T cells bind to specific antigen presented by phagocytes (antigen-presenting cell)
  3. This activates T-cell: Binding triggers rapid mitosis = T cells are cloned

14

Name 4 things that the cloned helper T-cells do

  • Activate cytotoxic T cells 
  • Activate B-cells to divide and secrete their antibodies
  • Develop into memory cells 
  • Release chemical signals that activate and stimulate phagocytes

15

Describe how cytotoxic T-cells kill infected cells

  1. Produce protein called perforin that makes holes in cell-surface membrane
  2. Holes means cell membrane becomes freely permeable
  3. Control of substances no longer controls and cell dies

16

Why is the action of T-cells most effective against viruses?

∵ they replicate inside cells, sacrificing these body cells prevents viruses from multiplying and infecting more cells

17

What is the role of macrophages in stimulating B lymphocytes?

  • Antigen in membrane presented to lymphocytes
  • Produce cytokinins

18

What are B-cells (B-lymphocytes)?

White blood cell that's covered with antibodies

19

What are antibodies?

  • Proteins that bind antigens to form antigen-antibody complex
    • Stimulate immune response

20

Describe how T-cells activate B-cells, which divide into plasma cells

  1. When antibody on surface of B-cells meets complementary shaped antigen = binds to it
  2. This, together with chemicals released from helper T-cells, activates B-cell = divides by mitosis
  3. Clonal selection: form clones/produce plasma cells
  4. Make antibodies 
  5. Plasma cells produce memory cells

21

What do plasma cells do?

Secrete loads of antibodies specific to antigen

callled monoclonal antibodies

22

Describe what antibodies do to destroy pathogens

  1. Antibody has 2 binding sites = can bind 2 pathogens at same time
  2. Means pathogens & antibodies become clumped together = called agglutination
  3. Phagocytes bind to antibodies and phagocytose many pathogens at once
  4. Process leads to destruction of pathogens carrying this antigen in body

23

All antibodies have same _____ region

All antibodies have same constant region

24

What does the constant region allow antibodies to do?

To bind to receptors on B-cells

25

What does the hinge region allow antibodies to do?

Allows flexibility so molecules can group more than one antigens

26

Why are antibodies specific to one antigen? (3)

  • Variable region has specific primary structure
  • Tertiary structure of binding site is complementary to bind with these antigens
  • Forms complex between antigen and antibody

27

What is the primary response?

When antigen enters body for 1st time & activates immune system

28

Why is the primary response slow?

∵ there aren't many B-cells that can make antibody needed to bind to pathogen

29

Primary Immune Response

After being exposed to antigens, T- and B-cells produce ____ ___

memory cells

30

Memory cells remain in body for ____ time

long

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