3.2.4 Cell recognition and the immune system Flashcards
Non-specific - Phagocytosis (3),
- Phagosome/vesicle fuses with lysosome;
- (pathogen) destroyed by lysozymes/hydrolytic enzymes;
- Antigen (from pathogen) displayed on cell membrane (of phagocyte/antigen presenting c
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;
Describe how presentation of
a virus antigen leads to the secretion of
an antibody against this virus antigen.
- Helper T cell / TH cell binds to the antigen (on the antigen-presenting cell / phagocyte);
- This helper T / TH cell stimulates a specific B cell;
- B cell clones
OR
B cell divides by mitosis; - (Forms) plasma cells that release antibodies;
What is antigen? (2
- Foreign protein;
- (that) stimulates an immune response/production of antibody
What is antibody? (2)
- A protein/immunoglobulin specific to an antigen;
- Produced by B cells OR Secreted by plasma cells;
Explain Antibody specificity (4)
- Antibody has (specific) tertiary structure
- Has binding site/ variable region which only binds to one antigen
- Antigen is only found on this particular (pathogen/cell/tissue)
- so antibody (only) binds to / forms antigen/antibody complex with these (pathogen/cell/tissue) destroying them
Explain Antigen-Antibody
complex formation (4)
- Antibody has 4 polypeptide chains and has a quaternary structure
- Antibody has a variable region which has a specific amino acid sequence/primary structure
- Shape of the binding site is complementary to the antigen
- Forming an antigen-antibody complex
Explain the Humoral Response (6)
- Antigen on surface of bacterium binds to surface protein / surface receptor on a (specific/single) B cell;
- (Activated) B cell divides by mitosis / produces clone;
- (Division) stimulated by cytokines / by T cells;
- B cells/plasma cells release antibodies;
- (Some) B cells become memory cells;
- Memory cells produce plasma / antibodies faster;
Give two types of cell, other
than pathogens, that can stimulate an
immune response.(2)
- (Cells from) other organisms/transplants;
- Abnormal/cancer/tumour (cells);
- (Cells) infected by virus;
- Antigen presenting cells
Draw a labelled diagram of an
antibody (3)
- Y shape showing two long and two short (polypeptide) chains correctly positioned;
- binding site labelled on the end of the branches of the Y of the antibody;
Accept one or two being labelled, if two both must be correct. - Variable region labelled /Constant region labelled / Disulfide bridge/bond labelled;
Describe and explain the role
of antibodies in stimulating
phagocytosis.
Do not include details about the
process of phagocytosis.
- Bind to antigen
OR
Are markers;
Accept opsonin for ‘marker’
Accept form (antibody-antigen) complexes/are complementary to antigen - (Antibodies) cause clumping/agglutination
OR
Attract phagocytes;
Compare Active and
Passive Immunity (6)
- 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;
Compare Primary
and
Secondary Response (4)
- Before vaccination no antibody released because patients not yet encountered vaccine/antigen/virus;
- Primary response/after first dose) activation/clonal selection/expansion of B cells into plasma cells;
- Plasma cells release antibodies;
- Secondary response/after second dose) memory cells produce more antibodies/produce antibodies more
quickly;
How does a vaccine produces an immune response (7)
- 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/plasma cell secretes large amounts of antibody;
- B cell divides to form clone all secreting/producing same antibody;
Explain why giving children
more than one vaccination develops
good immunity (2)
- (Production of more) memory cells;
- (So) higher concentration of (circulating) antibodies in blood
OR
(So) rapid production of antibodies (on further infection)
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; - (They) could (then) identify potential antigens (to use in the vaccine);
Describe how B lymphocytes
would respond to vaccination
- B cell (antibody) binds to (viral) specific/complementary receptor/antigen;
Accept B cell forms antigen-antibody complex - B cell clones
OR
B cell divides by mitosis; - Plasma cells release/produce (monoclonal) antibodies (against the virus);
- (B/plasma cells produce/develop) memory cells;
Describe and explain HIV treatment with anti-retroviral
drug AZT (6)
- Person (infected with HIV) has HIV DNA (in their DNA);
- New HIV (particles) still made;
- (AZT) inhibits reverse transcriptase;
- (AZT) stops replication of HIV;
- Stops destruction of more / newly infected T cells;
- So immune system continues to work (and AIDS does not develop);
Describe how HIV is replicated (5)
- 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);
Explain how HIV affects the
production of antibodies when AIDS
develops in a person. (3)
- Less/no antibody produced;
- (Because HIV) destroys helper T cells;
Accept ‘reduces number’ for ‘destroys’ - (So) few/no B cells activated / stimulated
OR
(So) few/no B cells undergo mitosis/differentiate/form plasma cells;
Describe the structure of the
human immunodeficiency virus
(HIV).(4)
- RNA (as genetic material);
Reject nucleus/DNA/plasmids. - Reverse transcriptase;
- (Protein) capsomeres/capsid;
Reject capsule. - (Phospho)lipid (viral) envelope
OR
Envelope made of membrane;
Reject if HIV has a cell membrane or a cell wall. - Attachment proteins;
What is a monoclonal antibody?
(3)
- Antibody specific/complementary to one antigen only
- Antibodies all the same and from one original plasma cell
- Derived from a hybridoma cell/fused B lymphocyte and cancer cell
Suggest monoclonal antibodies
help scientists to identify target cells (4)
- antigen in cell-surface membrane;
- Antibody is complementary;
- (So) binds/attaches to the ZO-1/protein;
- (Cells identified with) dye/stain/fluorescent marker linked to antibody;
Suggest how one antibody can
bind two different molecules (2)
- have a similar shape/structure;
- Antibody is complementary to both
Explain why antibody will only bind to target cell
- antibody has a (specific) tertiary structure;
- Has binding site / variable region that only binds to / complementary to one antigen;
- Antigen to this antibody (only) found on these nerve cells;
- So, antibody (only) binds to / forms antigen-antibody complex with these cells
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;