12.8 - Immunology

Question 1

IMMUNE RESPONSE

1) When the body is invaded by any pathogen, a series of responses ensure that the pathogen is..

ANTIGENS

2) An antigen is a molecule (usually a protein) that….

Answer 1

1) rapidly identified (as non self) and destroyed before too much damage is caused to the affected organism

2) stimulates an immune response that results in the production of a specific antibody.

Question 2

Give two types of cell, other than pathogens, that can stimulate an immune response. (3)

Answer 2

1) Cells from other organisms (transplants)
2) Abnormal / cancer / tumour cells
3) Cells infected by a virus

Question 3

PHAGOCYTOSIS

Describe the non-specific defence mechanisms that the body may launch against pathogens (5)

6) This process is _______ and works the same for any cell/pathogen that displays a non-self antigen. But it would take…

Describe how a phagocyte destroys a pathogen present in the blood. (3)

Answer 3

1) Pathogen is engulfed by the phagocyte
2) Engulfed pathogens enters the cytoplasm of the phagocyte in a vesicle (phagosome)
3) Lysosomes fuse with vesicle releasing digestive/hydrolytic enzymes
4) These break down/hydrolyse the pathogen
5) Waste materials are ejected from the cell by exocytosis.

[ also antigens are presented on the C.S.M and the phagocyte becomes an APC ]

6) far too long to destroy all invading pathogens in event of an infection, which may result in damage to tissue and organs. So we have more efficient systems which involve specific immunity.

1) Engulfs
2) Forming phagosome and fuses with lysosome
3) Enzymes hydrolyse pathogen

Question 4

Some white blood cells are phagocytic. Describe how these destroy bacteria. (5)

Answer 4

1) Phagocyte attracted to bacteria by chemicals / recognise antigens on bacteria as foreign
2) Engulf bacteria
3) Bacteria in vescile
4) Lysosome fuses with vesicle and empties enzymes into it
5) Bacteria is hydrolysed

Question 5

SPECIFIC CELLULAR RESPONSE - response of T cells - cell mediated immunity (primary response)

1) Specific TH cells can respond directly to a pathogen or its antigens or to APC that..
2) The TH cell with specific receptor molecule…
3) Once the TH cell binds, it…

NAME 5 ROLES OF TH CELLS

NAME 3 ROLES OF TC CELLS

Answer 5

1) presents the specifically complementary antigen to its receptors.
2) binds to presented antigen (on APC’s C.S.M)
3) is activated, then rapidly clones by mitosis to produce many TH cells with complementary receptors to the antigen.

1) Specific TH cell binds to APC
2) Release cytokines that attract phagocytes to area of infection
3) Release cytokines that activate cytotoxic killer t cells (Tc)
4) Activates a specifically complementary B cell
5) Forms memory TH cells

1) Locate and destroys infected body cells that present the correct antigen
2) Binds to APC
3) Releases perforin protein which creates holes in the CSM which destroys the APC

Question 6

Explain how the humoral response leads to immunity. (3)

Answer 6

1) B cells, specific to the antigen, reproduce by mitosis
2) B cells produce plasma and memory cells
3) Second infection produces antibodies in larger quantities and quicker.

Question 7

HUMORAL RESPONSE - B CELL ACTIVATION

1) A specific TH cell with the correct receptor binds to..
2) The specific TH releases..
3) The B cell then differentiates into: plasma cells and memory cells:

Answer 7

1) the presented antigen and then locates and activates a specifically complementary B cell
2) Cytokine chemicals that signal the specific B cell to clone by mitosis
3) Plasma - produce + secrete vast quantities of specific antibodies into blood plasma
Memory - remain in body to respond to pathogen rapidly and extensively should there be a future re-infection.

Question 8

ANTIBODIES

1) An antibody is a protein made in response to a….
2) They are complex proteins with a __________ structure made up of _____- polypeptide chains. The overall shape is_______
3) The main part of it that is the same in all antibodies is the..
4) The variable regions have a different…
5) The binding site is..

HOW DO ANTIBODIES ASSIST TO DESTRUCT PATHOGENS?

1) Agglutination: specific antibodies bind to..
2) Opsonisation: marking pathogens so that
3) Lysis: bind to antigens and lead to…
4) Anti-toxin and anti-venom: bind to toxins or venom to..
5) Prevent pathogen r..

Answer 8

1) foreign antigen - has binding sites which bind specifically to an antigen. A specific antibody is produced by a specific plasma cell.
2) quarternary, 4, Y-shaped
3) constant region
4) Primary + tertiary structure
5) specific which is different for each antibody.

1) the antigens on the pathogen and clump them together
2) phagocytes recognise them and destroy them more efficiently
3) destruction of pathogens membrane
4) Prevent these molecules from binding to their complementary target regions.
5) replication

Question 9

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Explain how. (7)

Answer 9

1) Vaccine contains antigen from pathogen
2) Macrophage presents antigen on surface
3) TH cell with complementary receptor binds to antigen
4) T cell stimulates B cell
5) With complementary antibody on its surface
6) B cell divides to form clones forming the same antibody
7) B cell secretes large amounts of antibody

Question 10

Describe and explain the role of antibodies in stimulating phagocytosis. (2)

Answer 10

1) Bind to antigen
2) Cause clumping / agglutination or attract phagocytes

Question 11

State why some antibodies are referred to as monoclonal (1)

Answer 11

1) They are produced from a single clone of B cells.

Question 12

What is the role of the disulphide bridge in forming the 4* structure of an antibody?

Answer 12

Joins two different polypeptides

Question 13

Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why. (3)

Answer 13

1) Specific 1*
2) Specific 3*
3) Only binds to one antigen

Question 14

Describe the difference between active and passive immunity (5)

Answer 14

1) Active involves production of antibody, passive involves antibody introduced by outside source
2) Active = involves memory cells, passive = doesn’t
3) Active long term because antibodies are produced in response, Passive short term, as antibody given is broken down
4) Active takes time to develop, passive is fast acting
5) Active = exposure to antigen, passive = no exposure

Question 15

Describe the structure of HIV. (5)

Answer 15

1) RNA (as genetic material)
2) Reverse transcriptase enzyme
3) Capsid (surrounds above ^)
4) Lipid envelope (the membrane)
5) Attachment proteins)

Question 16

Describe how the HIV is replicated once inside TH cells. (4)

Answer 16

1) RNA converted into DNA with reverse transcriptase
2) DNA inserted into TH genome
3) DNA transcribed into HIV mRNA
4) HIV mRNA translated into viral proteins

Question 17

Explain how HIV affects the production of antibodies when AIDS develops in a person. (3)

Answer 17

1) Less/no antibody produced
2) Because HIV destroys TH cells
3) So few/no B cells activated so few/no B cells undergo mitosis forming plasma cells.

Question 18

Describe how a person infected with HIV will develop AIDS and die of secondary infections. (4)

Answer 18

1) High viral load leads to increased destruction of TH cells
2) LEss activation of B cells
3) Less production of plasma cells / antibodies
4) Less able to destroy pathogens

Question 19

Describe the role of antibodies in producing a positive result in an ELISA test. (4)

Answer 19

1) First antibody attaches to antigen
2) Second antibody with enzyme attached is added
3) Second antibody attaches to antigen
4) Substrate added and colour changes.

Question 20

ANTIBIOTICS

Antibiotics work by preventing…

Answer 20

bacteria making a normal cell wall (murein/peptidoglycan) by targeting 70S ribosomes.

SO bacteria can’t resist osmotic pressure and burst by increase in water volume in cell by osmosis

Viruses have a capsid than a murein cell wall so antibiotics cant act on them.