2.4 immune system EXAM questions Flashcards
Describe how HIV is replicated. (4)
- Attachment proteins attach to receptors on helper T cell/lymphocyte;
- Nucleic acid/RNA enters cell;
- Reverse transcriptase converts RNA to DNA;
- Viral protein/capsid/enzymes produced;
- Virus (particles) assembled and released (from cell);
Describe how the human immunodeficiency virus (HIV) is replicated once
inside helper T cells (TH cells). (4)
- RNA converted into DNA using reverse transcriptase;
Reject ‘messenger’ or ‘m’ before RNA - DNA incorporated/inserted into (helper T cell)
DNA/chromosome/genome/nucleus; - DNA transcribed into (HIV m)RNA;
Accept descriptions of transcription - (HIV mRNA) translated into (new) HIV/viral proteins (for
assembly into viral particles);
Describe how a phagocyte destroys a pathogen present in the blood. (3)
- Engulfs;
Accept endocytosis
OR
Description
Ignore ‘taken in’ - Forming vesicle/phagosome and fuses with lysosome;
- Enzymes digest/hydrolyse;
What is the role of the disulfide bridge in forming the quaternary structure
of an antibody? (1)
Joins two (different) polypeptides;
In Europe, viruses have infected a large number of frogs of different species. The
viruses are closely related and all belong to the Ranavirus group.
Previously, the viruses infected only one species of frog.
(a) Suggest and explain how the viruses became able to infect other species
of frog. (2)
- Mutation in the viral DNA/RNA/genome/genetic material;
Accept named examples mutations - Altered (tertiary structure of the) viral attachment protein;
- Allows it/attachment protein/virus to bind (to receptors of other
species);
Determining the genome of the viruses could allow scientists to develop a
vaccine.
Explain how (2)
(The scientists) could identify proteins (that derive from the genetic
code)
OR
(The scientists) could identify the proteome;
2. (They) could (then) identify potential antigens (to use in the vaccine);
What is a monoclonal antibody? (1)
(Antibodies with the) same tertiary structure
OR
(Antibody produced from) identical/cloned plasma cells/B cells/B
After a disease is diagnosed, monoclonal antibodies are used in some
medical treatments.
Give one example of using monoclonal antibodies in a medical treatment. (1)
Targets/binds/carries drug/medicine to specific cells/antigens/receptors
OR
Block antigens/receptors on cells;
Accept cancer/diseased cells (as a specific cell).
Ignore medical diagnosis/pregnancy/ PSA/ELISA test
Describe the role of antibodies in producing a positive result in an ELISA
test.
(4)
- (First) antibody binds/attaches /complementary (in shape) to antigen;
- (Second) antibody with enzyme attached is added;
- (Second) antibody attaches to antigen;
Accept (second) antibody attaches to (first) antibody
(indirect ELISA test). - (Substrate/solution added) and colour changes;
) When a person is bitten by a venomous snake, the snake injects a toxin
into the person. Antivenom is injected as treatment. Antivenom contains
antibodies against the snake toxin. This treatment is an example of passive
immunity.
Explain how the treatment with antivenom works and why it is essential to
use passive immunity, rather than active immunity (2)
- (Antivenom/Passive immunity) antibodies bind to the
toxin/venom/antigen and (causes) its destruction; - Active immunity would be too slow/slower;
Describe how phagocytosis of a virus leads to presentation of its antigens. (3)
- Phagosome / vesicle fuses with lysosome;
- (Virus) destroyed by lysozymes / hydrolytic enzymes;
- Peptides / antigen (from virus) are displayed on the cell
What is an antigen? (2)
- Foreign protein;
Accept glycoprotein / glycolipid / polysaccharide - (that) stimulates an immune response / production of antibody;
What is an antibody?
- A protein / immunoglobulin specific to an antigen;
- Produced by B cells
When a vaccine is given to a person, it leads to the production of
antibodies against a disease-causing organism. Describe how. (5)
) 1. Vaccine contains antigen from pathogen;
2. Macrophage presents antigen on its surface;
3. T cell with complementary receptor protein binds to antigen;
4. T cell stimulates B cell;
5. (With) complementary antibody on its surface;
6. B cell secretes large amounts of antibody;
7. B cell divides to form clone all secreting / producing same
antibody.
Describe the difference between active and passive immunity. (5)
- Active involves memory cells, passive does not;
- Active involves production of antibody by plasma cells /
memory cells; - Passive involves antibody introduced into body from outside /
named source; - Active long term, because antibody produced in response to
antigen; - Passive short term, because antibody (given) is broken down;
- Active (can) take time to develop / work, passive fast acting.
