M4 - Immunity - Lymphocytes, Phagocytes And Stuff

Question 1

What is phagocytosis

Answer 1

1. Detect presence of pathogen when receptors on its cell surface bind to antigens on the pathogen
2. Phagocyte then engulfs pathogen into an vesicle called PHAGOSOME
3. Lysosome will fuse with the phagosome to form a phagolysosome
4. Lysozymes will digest the pathogen and destroy it
5. Digested pathogen will be removed by exocytosis but will keep antigen to present on surface to alter other cells - now an antigen presenting cell

Question 2

Phagosome turns into what

Answer 2

Phagosome fuses with lysosome and turns into phagolysosome

Question 3

What is the T lymphocyte response

Answer 3

White blood cells which have different shaped receptors so they will each bind to a different antigen
When a T cell binds to an antigen it will become activated (clonal selection)
Once activated, clonal expansion takes place - divides by mitosis to produce clones

Question 4

What do t lymphocytes divide into

Answer 4

T helper cells - release interleukins to activate b lymphocytes
T killer cells - release perforin to perforate cell membrane to destroy it
T regulatory cells - suppress other immune cells and prevent them from attacking self cells
T memory cells - remain in bloodstream - if antigen detected again, it will divide into t helper, killer and regulatory cells

Question 5

How are B lymphocytes activated and what do they do

Answer 5

• Activated when t helper cells release cytokines or when antibodies on their surface bind to pathogens antigen
• When activated, b cells divide by mitosis and differentiate into two different cells - plasma or memory
• plasma cells produce antibodies complementary to antigen
• memory cells remain in bloodstream. If antigen detected again, it will divide into plasma cells

Question 6

Antibody structure

Answer 6

• quaternary structure of 4 polypeptide chains (two heavy and two light) - held by disulfide bridges
• variable region (different in different antibodies) - where antigen binding site is
• constant region is same for all antibodies - has binding site which allows binding to immune cells
• Hinge region provides antibody with flexibility

Question 7

What do antibodies do to destroy pathogens

Answer 7

• agglutination
• neutralising toxins
• blocking access to human cells

Question 8

What is agglutination

Answer 8

Antibodies have two binding sites which means they can bind to two antigens at once - this clumps them together
Phagocytes can then digest more at a time and more efficiently

Question 9

What are Neutralising toxins

Answer 9

Some Pathogens release toxins and antibodies can bind to these toxins and render them harmless
Antibody-toxin complex can then be destroyed by phagocytes

Question 10

What is blocking access to human cells

Answer 10

When antibodies bind to antigens they can’t fit on any receptor sites of our cells, meaning they can’t get in

Question 11

Primary immune response

Answer 11

Infected for first time and uses non specific and specific responses
It’s slow bc it takes time for correct b cell to be activated and divide into plasma cells
T and B Memory cells produced

Question 12

Secondary immune response

Answer 12

If reinfected with same pathogen, t and b memory cells will recognise the antigens and start dividing
T memory - t killer
B memory - plasma cells

Question 13

Active immunity

Answer 13

When body makes own antibodies after being stimulated by antigens

Question 14

Active Natural and artificial

Answer 14

Natural is when we catch a pathogen
Artificial is when a harmless pathogen is given to stimulate antibody production

Question 15

Passive immunity

Answer 15

Ready made antibodies produced but another organisms
Natural - babies receive antibodies from mother
Artificial - antibody injections given