Cell Recognition and the Immune System Flashcards
When a pathogen enters the body it may be destroyed by
phagocytosis. Describe how.
Phagocyte attracted by a substance /
recognises (foreign) antigen;
(Pathogen)engulfed / ingested;
Enclosed in vacuole / vesicle / phagosome;
(Vacuole) fuses / joins with lysosome;
Lysosome contains enzymes;
Pathogen digested / molecules hydrolysed;
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;
Explain the increase in specific plasma cells and
antibody in people infected with a particular virus.
- Antigen/glycoprotein on virus binds to/stimulates (a specific) B cell;
- (Binding causes) replication/cloning of B cell;
- Plasma cells/B cells release/produce antibodies;
Vaccines protect people against disease. Explain how.
- Vaccines contain antigens / antigens are injected;
- Dead pathogens / weakened pathogens;
- Memory cells made;
- On second exposure memory cells produce antibodies / become
active / recognise pathogens; - Rapidly produce antibodies / produces more antibodies;
- Antibodies destroy pathogens;
- Herd effect / fewer people to pass on disease;
Describe how vaccination can lead to protection against
bacterially caused diseases [6]
Antigen on the surface of bacteria binds
to surface receptor on a specific/single B
cell;
(Division) stimulated by cytokines / by T
cells;
(Activated) B cell divides by mitosis /
produces clone;
B plasma cells release antibodies;
(Some) B cells become memory cells;
Memory cells produce plasma /
antibodies faster;
Vaccines protect people against disease. Describe and explain how.
Vaccines contain antigens
Or dead pathogens / weakened pathogens;
The pathogen’s antigen binds to a surface receptor
on a specific/single B cell;
(Division) stimulated by cytokines / by T cells;
(Activated) B cell divides by mitosis / produces clone;
B plasma cells release antibodies;
(Some) B cells become memory cells;
On second exposure memory become active /
recognise pathogens;
Memory cells divide to make B plasma cells which
Rapidly produce antibodies / produces more
antibodies;
Antibodies destroy pathogens;
Herd effect / fewer people to pass on disease;
A vaccine can be used to produce immunity to diseases caused by
pathogens. Describe how memory cells are important in this process.
Memory cells produced/remain/stored (from
previous infection);
(When individual) comes into contact with
virus/antigen (again);
Rapid/secondary/greater response/many or more
antibodies produced;
Destroys virus/antigen before it can cause
harm/symptoms/ cancer;
Describe how B-lymphocytes respond when they are stimulated by
antigens.
divide by mitosis / form clones;
To produce plasma cells;
the plasma cells make antibodies;
The plasma cells produce memory cells
Describe how antibodies are produced in the body following a viral
infection.
virus contains antigen;
virus is engulfed by phagocyte;
The phagocyte presents the antigens to B-cell;
T-cells activate the B-cells
B cells divide by mitosis to form clones and
produce
plasma cells which produce antibodies;
The antibodies are specific to the virus’ antigen
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;
Specific helper T cell with complementary receptor binds to antigen;
The Helper T cell stimulates specific B cell;
The B-cell has antibody/receptor on its surface which is also
complementary to the pathogen’s antigen;
B cell divides by mitosis to make genetically identical B-plasma cells
B plasma cell all secrete large amounts of the same antibody;
Cells which have faulty receptor proteins can be destroyed by the immune system. Explain how.
Faulty protein recognised as an antigen/as a ‘foreign’ protein;
T cells will bind to faulty protein/to (this) ‘foreign’ protein;
(Sensitised) T cells will stimulate clonal selection of B cells;
(Resulting in) release of antibodies against faulty protein;
Explain why an antibody will only bind to a particular protein [2]
Antibody has a variable region with a specific tertiary structure;
Which is complementary to binding site on protein;
Describe the HIV lifecycle
The virus’s attachment proteins binds to the (CD4) receptor proteins on the surface of
T helper cells
The virus’s lipid envelope fuses with the cell membrane of the T helper cells
The protein capsid breaks down
RNA and enzymes (e.g. reverse transcriptase) of the virus are now released into the
cytoplasm of the T helper cell.
Reverse transcriptase converts the viral RNA to DNA.
The viral DNA is incorporated into the T helper cell’s DNA.
The viral DNA is transcribed into mRNA
Viral mRNA passes through the nuclear pore and attaches to a ribosome
Viral mRNA is translated into viral proteins that can be assembled into new HIV
particles.
HIV particles bud off the T helper cell (so that the Th cell’s membrane forms the lipid
envelope of the virus).
When HIV infects a human cell, the following events occur.
A single-stranded length of HIV DNA is made.
The human cell then makes a complementary strand to the HIV DNA
Describe how the complementary strand of HIV DNA Is made. [3]
Base pairing between Complementary nucleotides (A to T and C to G);
Nucleotides are joined together (to form new strand) so phosphodiester bonds form;
By DNA polymerase;
