Module 2 - Cell recognition and the immune system Flashcards
5 marks
Describe difference between active and passive immunity
- 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
- 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, passive fast acting.
5 marks
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how
- Vaccine contains antigen from pathogen
- Macrophage presents antigen on its surface
- T cell with complementary receptor protein binds to antigen;
- T cell stimulates B cell
- (With) complementary antibody on its surface
- B cell secretes large amounts of antibody
- B cell divides to form clone all secreting / producing same antibody.
How does passive immunity work
Passive involves antibody introduced into body from external source
Adding the antibody would cause agglutination and increase efficiency of phagocytosis
State one role of a helper T cell.
Stimulating cytotoxic T cells
Stimulating B cells
Stimulating phagocytes;
The human papilloma virus contains a double-stranded DNA genome.
Which components are found in a human papilloma virus? Choose one
* Capsid and attachment protein
* Capsid, attachment protein and reverse transcriptase
* Capsule and attachment protein
* Cell-surface membrane and attachment protein
Capsid and attachment protein
2 marks
Explain why viruses are described as acellular and non-living.
- Accelular= not made up of cells
- Non living= no metabolic reactions/ need a host cell to replicate
Give one reason why antibiotics are not effective against viruses.
doesnt have a cell wall
Define pathogen
Microorganism that causes disease/ an immune response
3 marks
Describe how phagocytosis of a virus leads to presentation of its antigens
- Phagosome/ vesicle fuses with lysosome
- Virus destroyed by lysozymes/ hydrolytic enzymes
- Antigen from virus are displayed on the cell membrane
3 marks
Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen
- T helper cell receptor binds to antigen on the antigen- presenting cell
- T helper cell stimulates a specific B cell
- B cell divides by mitosis
- Forms plasma cells that release antibodies
3 marks
Describe viral replication
- Attachment proteins attach to receptors
- Viral nucleic acid enters cell
- Reverse transcriptase converts RNA to DNA
- Cell produces viral proteins
- Virus assembled and released from cell
1 mark
There is currently no effective vaccine available for HIV. Suggest one reason why.
- (High rate of) mutation
- (High) genetic diversity
- HIV in cells could (still) spread infection
- HIV (DNA) embeds/inserts itself in host DNA
- Lack of funding/money (for research/development)
- HIV causes fewer T cells, so immune response (to the vaccine) does not happen
1 mark
Explain how the stain allowed the doctor to count the white blood cells amongst all the red blood cells.
White cells have a nucleus that stains but red cells do not
2 marks
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. Suggest and explain how the viruses became able to infect other species of frog.
- Mutation in the genetic material
- Altered tertiary structure of the viral attachment protein
- Allows attachment protein to bind to receptors of other species
4 marks
Describe how the human immunodeficiency virus (HIV) is replicated once inside helper T cells (TH cells).
- RNA converted into DNA using reverse transcriptase
- DNA inserted into helper T cell nucleus
- DNA transcribed into HIV mRNA
- HIV mRNA translated into viral proteins for assembly into viral particles
2 marks
No organelles are visible in the cytoplasm of this red blood cell.
Suggest why
Cytoplasm of red blood cell filled with haemoglobin.
2 marks
What is a monoclonal antibody
- Antibody with the same tertiary structure
- B plasma and memory cells produce antibodies
2 marks
Explain why a test line in elisa test is important
- Prevents false negative results
- Shows antibody has moved up strip and hasnt bound to antigen
6 marks
Explain the process of the ELISA test
- Antibodies complementary to antigen and are bound to bottom of the beaker
- When patient sample is added, target antigens bind to antibody
- Sample is washed to remove unbound antibodies
- Secondary antibodies added with enzyme bound
- Wash sample to remove unbound antibodies
- Substrate is added (colourless) which reacts with enzyme
- If target antigen is present, a colour change takes place
1 mark
Define antigenic variability
Mutations in DNA cause a changes to tertiary structure of antigens. E.g. different Covid variants
Explain primary and secondary immune responses
Primary response – memory cells made. Secondary response – Memory cells convert to Plasma [increase in Golgi, RER, mitochondria]. Many Antibodies produced. Rapidly.
Give examples of active and passive immunity
Active – immune response to pathogen or vaccine
Passive – breast milk or injecting antibodies
Outline how the ELISA test works in for the ‘test’ line in a Lateral Flow Test
‘Capture’, stationary monoclonal antibody binds to antigen. Monoclonal antibody with label [enzyme] binds to antigen. Substrate changes to coloured product in the presence of enzyme.
How could you use the immune response of different animals to analysis evolutionary relationships? [The precipitate method]
Give Protein antigens from Species A to Host animal – antibodies made.
Test those antibodies with Species B, C, D. The greater amount of precipitate [Antigen/Antibody complexes] – the more similar the Species B,C or D proteins are to Species A – so closer evolutionary relationship.
