Cell recognition and Immunity practise questions Flashcards
(18 cards)
Explain why antibodies are only effective against a specific pathogen (2 marks)
- Antigens on the pathogen are a specific shape/Have a specific tertiary structure
- Antigen-antibody complex forms
Describe the process of phagocytosis (4 marks but 6 possible points)
- Phagocyte attracted by a substance/ recognised foreign antigen
- Pathogen engulfed
- Enclosed in a vesicle/Phagosome
- Phagosome fuses with lysosome
- Lysosome contains hydrolytic enzymes
- Pathogen digested/hydrolysed
Scientists use an antibody to detect an antigen on teh bacterium that cuases stomach ulcers.
Explain why the antibody will only detect this antigen? (3 Marks)
- Antibody/Variable region has specific amino acid sequence/primary structure
- The shape/ tertiary structure on the binding iste is complementary to the antigen
- Antigen-Antibody complex forms
Antigens are proteins. Explain why a knowledge of antigens can show that animals are genetically similar
- Protein/Antigen production is determined by alleles/genes on DNA
- The more similar the proteins the more similar the alleles/more genetically similar
Give one reason why you should have straight lines plotted from point to point in data
Because it is impossible to predict values between points
Give two reasons why an increase in antibody production in mice will not neccesarily mean humans can have resistence to disease
- They only tested on mice-not represnetive of humans
- Not all diseases cured by antibodies
Some of the antigens found on the surface of tumour cells are also found
on the surface of healthy human cells.
Use this information to explain why treatment with an ADC often causes
side effects.
- ADC will bind to non-tumour/healthy cells;
Reject reference to active site - Cause death/damage of non-tumour/healthy cells
Describe how the human immunodeficiency virus (HIV) is replicated once
inside helper T cells (TH cells).
- 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);
Suggest and explain two further investigations that should be done before
this ADC is tested on human breast cancer patients.
- Tested on other mammals to check for safety/side effects;
Accept named mammal, eg rat - Tested on (healthy) humans to check for safety/side effects;
Accept: Tested on (healthy) human tissue/cells to
check for no side-effects - See if repeat doses stop the tumours regrowing (in Group J);
- Investigate different concentrations of ADC to find suitable/safe
dosage;
A disulfide bridge is labelled in the diagram above.
What is the role of the disulfide bridge in forming the quaternary structure
of an antibody?
Joins two (different) polypeptides;
6.
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.
) 1. Mutation in the viral DNA/RNA/genome/genetic material;
Accept named examples mutations
2. Altered (tertiary structure of the) viral attachment protein;
Accept ‘antigen’ for ‘attachment protein’
3. 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.
- (The scientists) could identify proteins (that derive from the genetic
code)
OR
(The scientists) could identify the proteome; - (They) could (then) identify potential antigens (to use in the vaccine);
Give one example of using monoclonal antibodies in a medical treatment.
Targets/binds/carries drug/medicine to specific cells/antigens/receptors
OR
Block antigens/receptors on cells;
Describe the role of antibodies in producing a positive result in an ELISA
test.
- (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;
Only award if enzyme mentioned.
Describe and explain the role of antibodies in stimulating phagocytosis.
Do not include details about the process of phagocytosis.
- Bind to antigen
- (Antibodies) cause clumping/agglutination
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.
(Antivenom/Passive immunity) antibodies bind to the
toxin/venom/antigen and (causes) its destruction;
2. Active immunity would be too slow/slower;
A mixture of venoms from several snakes of the same species is used.
Suggest why.
- May be different form of antigen/toxin (within one species)
OR
Snakes (within one species) may have different mutations/alleles; - Different antibodies (needed in the antivenom)
OR
(Several) antibodies complementary (to several antigens);
During the procedure shown in the chart the animals are under ongoing
observation by a vet.
Suggest one reason why
- (So) the animal does not suffer from the venom/vaccine/toxin;
- (So) the animal does not suffer anaemia/does not suffer as a result of
blood collection; - (So) the animal does not have pathogen that could be transferred to
humans;
