Topic 2 - Immunology and disease

Question 1

What is a pathogen?

Answer 1

A microorganism that causes (communicable) disease.

Question 2

What are the four types of pathogen?

Answer 2

Bacteria Fungi Viruses Protoctista

Question 3

What is the structure of a virus.

Answer 3

*Acellular - non living
*20-300nm (smaller than bacteria)
*Contain nucleic acids (DNA/RNA) in protein called capsid
*Has either a lipid envelope (HIV) or attachment proteins.

Question 4

Why does a high mutation rate make it difficult to develop a vaccine?

Answer 4

*mutation leads to antigens change.
*vaccine contains specific antigen.
*antibodies not complementary to antigen.

Question 5

What is the immune response to a virus that leads to antibody production?

Answer 5

*The virus antigen presented on surface of B cell/lymphocytes.
*Th Cell binds + stimulates B cell/lymphocytes to make clones - plasma cells.
*Plasma cells secrete antibodies that are complementary to virus antigen so bind to it - leading to it’s destruction.
*Memory cells produced.

Question 6

How is a pathogen destroyed by phagocytosis.

Answer 6

*Phagocyte recognises foreign antigens.
*Pathogen is engulfed and enclosed in phagosome.
*Vacuole fuses with lysosome - lysozymes released.
*Pathogen hydrolysed.
*Virus antigens presented on phagocytes surface.

Question 7

Why are antibodies only effective against a specific pathogen?

Answer 7

Antigens specific shape/tertiary structure. Antigen will only bind to antibody it’s complementary to. Antigen-antibody complex forms.

Question 8

What is an antigen?

Answer 8

A glycoprotein molecule on the surface of an organism recognised as non-self by the immune system. So stimulates an immune response.

Question 9

What is an antibody?

Answer 9

Proteins secreted by plasma cells that have binding sites that are specific to a specific antigen - which they then form an antigen-antibody complex with.

Question 10

Why do whole cell vaccines produce a greater range of antibodies in organisms?

Answer 10

Because they contain a greater range of antigens - and each antigen stimulates its own immune response.

Question 11

Two ways in which a pathogen may cause disease once it has entered the body:

Answer 11

*Produce Toxins
*Damage Cells

Question 12

Use knowledge of protein structure to explain why tests using monoclonal antibodies are specific:

Answer 12

*Specific order of AA (amino acids).
*Specific tertiary structure.
*Only complementary and binds to one antigen.

Question 13

What is a monoclonal antibody?

Answer 13

Antibodies with the same tertiary structure from the same plasma cell.

Question 14

How does the ELISA Test work to show a positive result?

Answer 14

*Antibody binds to complementary antigen.
*2nd antibody with enzyme attached added.
*2nd antibody attaches to antigen/first antibody.
*Substrate added and binds to enzyme resulting in colour change. (if positive)

Question 15

How is HIV replicated?

Answer 15

*attachment proteins on the HIV bind to receptors on T-cell.
*Virus RNA enters host T cell.
*reverse transcriptase converts RNA to DNA.
*Viral proteins produced (after DNA is transcribed into HIV mRNA) and assembled to produce viral particles.
*lyse out of cell

Question 16

Two types of cell other than pathogens which can stimulate an immune response.

Answer 16

*Cells from transplants
*abnormal cells eg cancer

Question 17

How were viruses able to infect other species?

Answer 17

Mutation in viral DNA
-> altered tertiary structure of viral attachment protein

Question 18

How could determining genome of viruses allow scientists to develop a vaccine?

Answer 18

They could identify proteins derived from genetic code.
Identify potential antigens to use in vaccine.

Question 19

What is the structure of HIV (Exam Q)

Answer 19

RNA as genetic material and reverser transcriptase RNA enclosed within a protein capsid. Has a phospholipid viral envelope.

Question 20

Describe how HIV is replicated:

Answer 20

• HIV’s attachment proteins bind to receptor proteins on the surface of T lymphocytes.
• HIV injects it’s RNA into host cell’s genome.
• Reverse transcriptase converts RNA to DNA
• DNA transcribed into HIV mRNA.
• mRNA translated into viral proteins and enzymes which are then produced.
• Then virus particles are assembled and released from the cell ( lyses out of the cell).

Question 21

Describe how a drug used to treat tumour cells (by binding to it’s surface receptors) causing the tumour cell’s destruction often causes side effects.

Answer 21

• because the drug will also bind to surface cell membranes on healthy cells
• then leading to the destruction of the healthy cell

Question 22

Suggest two investigations that should be made before the drug to treat tumour cells is used on human breast cancer patients.

Answer 22

• trials on healthy human volunteers -> to determine side effects
• investigate diff cons of drug to find a safe and suitable dosage

Question 23

How to evaluate use of certain treatments for HIV.

Answer 23

• may only work for certain type of HIV
• does it work in the long term -> have they tested
• are other forms of treatment still needed -> eg. chemotherapy + radiotherapy

Question 24

Give two types of cell other than pathogens which can stimulate an immune response:

Answer 24

• foreign cells
• tumour cells

Question 25

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

Answer 25

Connect the diff polypeptide strands together.

Question 26

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

Answer 26

- HIV attacks T-cells -> AIDS develops when low levels of T-cells become critical. - T-cells stimulate B lymphocytes to divide to produce antibodies. - So antibodies not produced if person has AIDS.

Question 27

Give one example of using monoclonal antibodies in a medical treatment:

Answer 27

Carries drugs to specific cell.

Question 28

Describe and explain the role of antibodies in stimulating phagocytosis.

Answer 28

- Antibodies form antigen-antibody complexes - act as a marker that attracts phagocytes - cause agglutination (of the cell w antigen on it)

Question 29

Looking at effectiveness of injections for vaccine on immune responses in named organism.

Answer 29

- Later ones usually more effective - mean antibody levels above protective antibody conc. - mean antibody conc usually inc with each simultaneous vaccine - first usually protects some organisms - later usually protects all organisms - does antibody dec rapidly after 3rd injection?

Question 30

Suggest a practical methods scientists could use to test if organisms in experiment had formed memory B cells after a certain number of vaccines?

Answer 30

- inject vaccine again - memory cells/lymphocytes present if faster immune response

Question 31

How does treatment with antivenom work and why is it essential to use passive immunity rather than active immunity?

Answer 31

- passive immunity has much faster response - antibodies bind to antigen on venom and cause its destruction

Question 32

Why is a mixture of venoms from several snakes of the same species used to make antivenom?

Answer 32

- cover a range of diff antibodies - bc diff antibodies contained in diff snakes

Question 33

Animals can be used to produce antivenom. Why do animals undergo observation by vets during this procedure?

Answer 33

- to ensure no negative effects on animals - and so that can check animal does not have pathogen that can be transferred to humans

Question 34

In a vaccination program why are animals initially injected with a small amount of antigen and then later injected with a larger volume of antigen?

Answer 34

- first injection will initiate smaller immune response - B lymphocytes specific to antigen replicate by mitosis and some form memory cells. - larger and faster immune response will occur after 2nd injection

Question 35

Suggest how a treatment drug for AIDS can slow development of AIDS without destroying HIV.

Answer 35

- person has HIV DNA in their DNA - New HIV particles still made - drug may inhibit reverse transcriptase (or other named process) - so stop new HIV particles making HIV DNA

Question 36

Suggest and explain two advantages of using HAART ( highly active antiretroviral therapy)

Answer 36

- slows AIDS development as HIV resistant to other named treatment is destroyed - no new HIV particles made -> therefore HAART may interfere with viral protein synthesis

Question 37

Suggest how the immune response to a viral protein (that is very similar to a human protein) can lead to destruction of the human protein.

Answer 37

- antibodies complementary to virus antigen - also bind to human protein bc similar - leading to their destruction

Question 38

Describe how vaccination can protect against infections and disease etc.

Answer 38

- Macrophage presents antigens on it's surface - foreign antigen binds to surface receptor on specific B lymphocyte - B lymphocyte stimulated to divide by TH cells ( that have complementary receptor to bind to antigen) by mitosis - Form plasma cells which secrete antibodies - some B lymphocytes become memory cells - memory cells can produce antibodies faster and at larger quantities protecting against future infection

Question 39

What are the differences between active and passive immunity?

Answer 39

Active - immune systems own response - slower response - longer term due to memory cells Passive - injecting antibodies - quick response - only short term response