Section 2 - Unit 5: Cell Recognition and the Immune System Flashcards
Describe how giving vaccines lead to the production of antibodies against viruses (4 marks)
4 from:
- Vaccine contains antigen
- Displayed on antigen-presenting cells
- Specific helper T cell detect antigen and stimulate specific B cell
- B cell divides through mitosis to form clones to give plasma cells
- B cell/plasma cell produces antibodies against the virus
Explain the increase in specific plasma cells and antibodies in people infected with a virus (2 marks)
- Antigen stimulates B cell to replicate
- B cells produce antibodies
Explain how a blood transfusion from a patient recently recovered from a virus may be an effective treatment for a person that has recently caught the virus (3 marks)
3 from:
- Recovered patient would have many antibodies
- The transfusion would contain antibodies
- That can bind to the virus antigen
- So the virus will be destroyed
Explain why a high mutation rate makes it difficult to develop a vaccine (3 marks)
- High mutation leads to the antigens changing
- The vaccine would only contain a specific antigen
- And so the antibodies won’t be complementary to the changed antigens
Describe the differences between active and passive immunity (5 marks)
5 from:
- Active involves memory cells, passive doesn’t
- Active involves production of antibody by plasma cells/memory cells
- Passive involves antibody introduced into body from outside/named source
- Active is long term, because antibody produced in response to antigen
- Passive is short term, because antibody given is broken down
- Active can take time to work, passive fast acting
Explain why cells in tumours with faulty receptor proteins can be destroyed by the immune system (3 marks)
- Faulty protein recognised as a foreign antigen
- T cells will bind to faulty protein
- And stimulate the clonal selection of B cells
- Resulting in release of antibodies against faulty protein
State two ways in which pathogens can cause disease (2 marks)
- Release toxins
- Kill cells/tissues
Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar. Explain in reference to water potential how putting honey on a cut can kill bacteria (3 marks)
- Honey has a lower water potential than bacterial cells
- Water moves out of cells into honey via diffusion
- The loss of water stops metabolic reactions and kills bacteria
Suggest why 100% of a population do not need to be vaccinated in order to be effective in preventing the spread of a disease (2 marks)
- More people immune
- So unvaccinated people are less likely to contact infected people
Describe how bacteria are destroyed by phagocytes (3 marks)
- Phagocyte engulfs bacteria to form a vesicle
- Lysosome empties its enzymes into the vesicle
- The enzymes digest/hydrolyse the bacteria
Give two structures a bacterial cell may have that a white blood cell does not have
- Plasmid
- Flagellum
Suggest two reasons why neither the volunteers or scientists knowing if a particular volunteer receives the vaccine or placebo makes the scientists’ results more reliable (2 marks)
- Scientists can’t show bias
- Volunteers can’t show psychological effects
Suggest how a vaccine against nicotine could help people to stop smoking (3 marks)
- Antibodies bind to nicotine
- So nicotine doesn’t reach the brain
- So smoking won’t satisfy their addiction
Define antigen (2 mark)
- Molecule/protein
- That stimulates an immune response
Suggest two reasons why antigens aren’t able to pass through the cell surface membranes of epithelial cells (2 marks)
- Not lipid soluble
- Too large
Explain why antibodies only detect specific antigens (3 marks)
- Antibodies have a specific amino acid sequence
- Tertiary structure of binding site is complementary to these antigens
- Forms complex between antigen and antibody
Explain how vaccines protect people against disease (5 marks)
- Vaccines contain weakened pathogens
- Memory cells made
- On second exposure memory cells recognise antigens
- And rapidly produce antibodies
- Antibodies destroy pathogens
Explain why monoclonal antibodies are referred to as monoclonal (1 mark)
- Antibodies produced from a single clone of B cells
Explain why destruction of phagocytes causes the lungs to be more susceptible to infections (2 marks)
- Phagocytes engulf/ingest/destroy pathogens
- Lung diseases are caused if pathogens aren’t destroyed
Describe how phagocytes and lysosomes are involved in destroying microorganisms (3 marks)
- Phagocytes engulf pathogens
- And enclose them in a vacuole
- Lysosomes have enzymes
- Which digest the microorganisms
Describe how B-lymphocytes respond when they are stimulated by antigens (4 marks)
- Divide by mitosis
- To produce plasma cells
- Which make antibodies
- And produce memory cells
Explain why it is important to wash the well at the start of Step 4 in tests like ELISA (2 marks)
- Removes unbound second antibodies
- Otherwise enzymes may change colour due to false positive
Explain why injecting antibodies into a person doesn’t give them long lasting protection against a disease (2 mark)
- Passive immunity
- So no memory cells produced
- Once antibodies are broken down, no further antibodies are produced
Describe how antibodies are produced in the body following a viral infection (6 marks)
- Virus contains an antigen
- Which is engulfed by a phagocyte
- The phagocyte presents the antigen to B-cell
- B-cells become activated
- To divide and form clones
- By mitosis
- Plasma cells produce antibodies
- Antibodies are specific to the antigen
Explain one advantage of using antibodies from plants to treat diseases rather than antibodies produced in an experimental animal (1 mark)
- Fewer ethical issues
OR - Less risk of infection
Explain why it’s important to use sterile techniques whilst culturing bacteria (2 marks)
- To prevent contamination of apparatus with other bacteria
- To prevent release of bacteria into air
Define monoclonal antibody (2 marks)
- A clone of B-lymphocytes
- Formed from one type of plasma cell
Suggest why it is necessary to give two injections of a vaccine (1 mark)
- One dose doesn’t give enough antibodies to be effective
Describe how T lymphocytes recognise and respond to the influenza virus (2 marks)
- T lymphocyte receptors recognise the shape of the antigen
- And stimulate the production of a clone of B-cells
- To destroy the virus
Explain how antigenic variability has caused some people to become infected more than once with the influenza virus (2 marks)
- T memory cells do not recognise new antigen
- And antibodies previously produced are not effective
- As their shape is not complementary to the new antigen
Describe the role of macrophages in stimulating B lymphocytes (1 mark)
- Macrophages present the antigen in their membrane to the lymphocytes
Describe how HIV is replicated after it has entered a human cell (4 marks)
- Reverse transcriptase
- Enzyme uses RNA to make DNA
- DNA joined to host cell’s DNA
- DNA used to make HIV RNA
- HIV proteins
- Made at the host cell’s ribosomes
- New virus particles are made
- And they bud off from the membrane of the host cell
Explain how the destruction of T-cells by HIV can lead to the death of an infected person (2 mark)
- Not enough T-cells to activate B-cells
- So person is unable to fight opportunistic infections
Explain what the clear zones around some of the discs containing antibiotic show in an experiment (2 marks)
- Antibiotic has diffused into the agar
- And killed/inhibited bacteria
Give two ways in which antibiotics can prevent bacterial growth (2 marks)
- Disrupts cell wall
- Stops DNA replication
Give two reasons why it’s important to use sterile techniques during an antibiotic investigation (2 marks)
- To prevent contamination of apparatus with other microorganisms
- To prevent release of bacteria into air
Suggest why an effective antibiotic may produce only a small clear zone (1 mark)
- It diffuses more slowly through the bacteria
Describe the structure of a plasma membrane and explain how different substances are able to pass through the membrane by diffusion (6 marks)
- Phospholipids forming bilayer
- Heads on the outside
- Proteins such as carrier, channel, intrinsic, etc. are present
- Other molecules such as cholesterol or glycoprotein
- Substances move down concentration gradient
- Water/ions move through channel proteins
- Small/lipid soluble molecules pass between through phospholipid layer
- Carrier proteins involved with facilitated diffusion
Explain how antigenic variability has caused some people to become infected more than once with influenza viruses (2 marks)
- Memory cells do not recognise new antigens
- So antibodies previously produced are not effective as the shape is not complementary to the new antigen
Explain using your knowledge of antigens why companies that create influenza vaccines find it useful to have information about the various influenza strains (2 marks)
- Vaccines only work against certain strains since they all have different antigens
- This enables the company to target the strain likely to be prevalent later on
State the steps of the ELISA test (5 marks)
- Sample is added to well in test plate
- Plate is washed to remove unbound protein
- Add antibodies
- Wash to remove unbound antibodies
- Add colourless solution
Define antibody (2 marks)
- Protein
- Specific to an antigen
- Complementary shape
During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom. Use your knowledge of the humoral immune response to explain this vaccination programme (3 marks)
- B cells specific to the venom reproduce by mitosis
- (B cells produce) plasma cells and memory cells
- The second dose produces antibodies (in secondary immune response) in higher concentration and quickly
Suggest one reason why vaccinating a large number of people would reduce significantly the spread of HPV through the population (2 marks)
- Virus cannot replicate / is destroyed / is not carried (in vaccinated people)
- Non-vaccinated people more likely to contact vaccinated people
Describe how B lymphocytes would respond to vaccination against viruses (4 marks)
- B cell binds to (viral) complementary antigen
- B cell clones OR divides by mitosis
- Plasma cells release/produce (monoclonal) antibodies (against the virus)
- (B/plasma cells produce/develop) memory cells
