immunity Flashcards
student used sterilised pipette to transfer E.coli into each culture, suggest why number of E.coli cells in each culture might have been lower if student had not used a sterilised pipette (2)
- unknown bacteria introduced
- these bacteria use food and space
explain how a fetus is protected against pathogens that infect it’s mother during pregnancy (3)
- antibodies from mother are complementary
- to pathogens crossing the placenta
- giving passive immunity in fetus
suggest why there has been a recent increase in number of children catching measles (1)
reduced vaccination in children
explain why giving children more than one tetanus vaccination develops good immunity against tetanus (2)
- more memory cells
- higher concentration of antibodies
define immunity
the ability of an organism to resist infection
give the 2 types of white blood cells and state if they are specific/non-specific
phagocytes- non-specific
lymphocytes- specific
define self-cell and non-self cell
self- the body’s own cells and molecules
non-self- foreign cells
give the 2 types of lymphocytes and where they mature and what they are involved in
B lymphocytes- mature in bone marrow, involved in humoral immunity
T lymphocytes- mature in thymus gland, involved in cell mediated response
what is an antigen presenting cell and give 2 examples
a cell that presents a non-self antigen on it’s surface
e.g. infected body cell, transplanted organ cell
what is the cell mediated response
T cells respond to antigens on the surface of cells
how many polypeptides in an antibody and what bonds link them
4
disulfide bridges
what is a monoclonal antibody (1)
Antibodies with the same tertiary structure
OR
Antibody produced from cloned plasma cells/B cells
what is vaccination
introduction of disease antigens into the body
what is a vaccine
small amount of weakened/dead pathogen or antigen introduced in mouth or by injection
what is herd immunity
if a large proportion of population is vaccinated, it is difficult for pathogen to spread
describe antigen variability
pathogen’s DNA can mutate frequently, antigen shape changes, memory cells store memory of old antigen shape so not effective anymore
give 3 features of HIV
- lipid envelope
- reverse transcriptase
- RNA
explain how HIV replicates (4)
- Attachment proteins attach to receptors on helper T cell
- RNA enters cell;
- Reverse transcriptase converts RNA to DNA;
- Viral proteins produced;
- Virus particles assembled and released from cell;
Describe how the human immunodeficiency virus (HIV) is replicated once
inside helper T cells (4)
- RNA converted into DNA using reverse transcriptase;
- DNA inserted into helper T cell’s DNA
- DNA transcribed into HIV mRNA;
- HIV mRNA translated into new HIV proteins for
assembly into viral particles
Describe how a phagocyte destroys a pathogen present in the blood (3)
- phagocyte engulfs pathogen;
- Forms phagosome and fuses with lysosome;
- lysozomes hydrolyse pathogen;
Give two types of cell, other than pathogens, that can stimulate an immune
response (2)
- Cells from transplants;
2.Abnormal/cancer cells;
- Cells infected by virus;
give the role of the disulfide bridge in forming the quaternary structure
of an antibody (1)
Joins two different polypeptides;
Explain how HIV affects the production of antibodies when AIDS develops
in a person (3)
- less antibody produced;
- Because HIV destroys helper T cells;
- less B cells activated
viruses have infected a large number of frogs of different species. Previously, the viruses infected only 1 species of frog.
Suggest and explain how the viruses became able to infect other species
of frogs (3)
- Mutation in the viral DNA/RNA/genome/genetic material;
- Altered tertiary structure of viral attachment protein;
- Attachment protein can bind to receptors of other
species
Determining the genome of the viruses could allow scientists to develop a
vaccine.
Explain how (2)
- they could identify proteins that derive from the genetic code
- They could then identify antigens to use in the vaccine
Describe how the B lymphocytes of a frog would respond to vaccination
against the virus. (3)
- B cell antibody binds to viral complementary
antigen; - B cell clones
- Plasma cells
produce monoclonal antibodies against the
virus - plasma cells produce memory cells;
Give one example of using monoclonal antibodies in a medical treatment (1)
targets specific cells e.g. cancer cells
OR
Block antigens on cells;
Describe the role of antibodies in producing a positive result in an ELISA
test (4)
- First antibody binds to complementary antigen;
- Second antibody with enzyme attached is added;
- Second antibody attaches to antigen;
- Substrate added and colour changes;
Describe and explain the role of antibodies in stimulating phagocytosis (2)
- bind to antigen
- cause agglutination
Antivenom contains
antibodies against snake toxin.Explain how treatment with antivenom works and why its essential to
use passive immunity, not active immunity. (2)
- Antivenom antibodies bind to the
antigen and destroy it - Active immunity would be too slow
During vaccination, animal initially injected with small volume of
venom. 2 weeks later, its injected with larger volume of venom.
Use knowledge of humoral immune response to explain this
vaccination programme. (3)
- B cells specific to the venom reproduce by mitosis;
- B cells produce plasma cells and memory cells;
- second dose produces antibodies in higher concentration and quickly
Describe how phagocytosis of a virus leads to presentation of its antigens (3)
- Phagosome fuses with lysosome;
- Virus destroyed by lysozymes
- antigen from virus are displayed on the cell
membrane;
Describe how presentation of a virus antigen leads to the secretion of an
antibody against this virus antigen (3)
- Helper T cell binds to antigen on the antigen-presenting cell
- This helper T cell stimulates a specific B cell;
- B cell clones/ divides by mitosis
- Forms plasma cells that release antibodies
define antigen (2)
- Foreign protein;
- that stimulates an immune response
define antibody (2)
- A protein 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)
- 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 producing same
antibody.
Bacterial meningitis is a fatal disease affecting membranes around
the brain. Neisseria meningitidis (Nm) is a leading cause of it.
children are vaccinated against this disease. Describe how
vaccination can lead to protection against bacterial meningitis.
(6)
- Antigen on surface of Nm bacterium binds to surface receptor on a specific B cell.
- Activated B cell divides by mitosis
- Division stimulated by by T cells;
- B cells / plasma cells release antibodies;
- Some B cells become memory cells;
- Memory cells produce plasma cells / antibodies faster
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 source
- Active is long term, because antibody produced in response to
antigen; - Passive is short term, because antibody given is broken down;
- Active takes time to work, passive is fast acting.
vaccines protect people against disease. explain how (5)
1.vaccines contain antigens/ weakened pathogens
- memory cells made
- on second exposure memory cells recognise pathogens
- they rapidly produce antibodies
- antibodies destroy pathogens
some white blood cells are phagocytic. describe how these destroy bacteria (4)
- phagocyte attracted to bacteria by chemicals
- engulf bacteria
- bacteria in vesicle
- lysosome fuses with vesicle
- bacteria hydrolysed
