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AQA AS Biology > Section 2 - Unit 5: Cell Recognition and the Immune System > Flashcards

Section 2 - Unit 5: Cell Recognition and the Immune System Flashcards

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1
Q

Describe how giving vaccines lead to the production of antibodies against viruses (4 marks)

A

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
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2
Q

Explain the increase in specific plasma cells and antibodies in people infected with a virus (2 marks)

A
  • Antigen stimulates B cell to replicate

- B cells produce antibodies

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3
Q

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)

A

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
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4
Q

Explain why a high mutation rate makes it difficult to develop a vaccine (3 marks)

A
  • 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
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5
Q

Describe the differences between active and passive immunity (5 marks)

A

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
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6
Q

Explain why cells in tumours with faulty receptor proteins can be destroyed by the immune system (3 marks)

A
  • 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
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7
Q

State two ways in which pathogens can cause disease (2 marks)

A
  • Release toxins

- Kill cells/tissues

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8
Q

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)

A
  • 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
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9
Q

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)

A
  • More people immune

- So unvaccinated people are less likely to contact infected people

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10
Q

Describe how bacteria are destroyed by phagocytes (3 marks)

A
  • Phagocyte engulfs bacteria to form a vesicle
  • Lysosome empties its enzymes into the vesicle
  • The enzymes digest/hydrolyse the bacteria
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11
Q

Give two structures a bacterial cell may have that a white blood cell does not have

A
  • Plasmid

- Flagellum

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12
Q

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)

A
  • Scientists can’t show bias

- Volunteers can’t show psychological effects

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13
Q

Suggest how a vaccine against nicotine could help people to stop smoking (3 marks)

A
  • Antibodies bind to nicotine
  • So nicotine doesn’t reach the brain
  • So smoking won’t satisfy their addiction
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14
Q

Define antigen (2 mark)

A
  • Molecule/protein

- That stimulates an immune response

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15
Q

Suggest two reasons why antigens aren’t able to pass through the cell surface membranes of epithelial cells (2 marks)

A
  • Not lipid soluble

- Too large

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16
Q

Explain why antibodies only detect specific antigens (3 marks)

A
  • Antibodies have a specific amino acid sequence
  • Tertiary structure of binding site is complementary to these antigens
  • Forms complex between antigen and antibody
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17
Q

Explain how vaccines protect people against disease (5 marks)

A
  • Vaccines contain weakened pathogens
  • Memory cells made
  • On second exposure memory cells recognise antigens
  • And rapidly produce antibodies
  • Antibodies destroy pathogens
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18
Q

Explain why monoclonal antibodies are referred to as monoclonal (1 mark)

A
  • Antibodies produced from a single clone of B cells
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19
Q

Explain why destruction of phagocytes causes the lungs to be more susceptible to infections (2 marks)

A
  • Phagocytes engulf/ingest/destroy pathogens

- Lung diseases are caused if pathogens aren’t destroyed

20
Q

Describe how phagocytes and lysosomes are involved in destroying microorganisms (3 marks)

A
  • Phagocytes engulf pathogens
  • And enclose them in a vacuole
  • Lysosomes have enzymes
  • Which digest the microorganisms
21
Q

Describe how B-lymphocytes respond when they are stimulated by antigens (4 marks)

A
  • Divide by mitosis
  • To produce plasma cells
  • Which make antibodies
  • And produce memory cells
22
Q

Explain why it is important to wash the well at the start of Step 4 in tests like ELISA (2 marks)

A
  • Removes unbound second antibodies

- Otherwise enzymes may change colour due to false positive

23
Q

Explain why injecting antibodies into a person doesn’t give them long lasting protection against a disease (2 mark)

A
  • Passive immunity
  • So no memory cells produced
  • Once antibodies are broken down, no further antibodies are produced
24
Q

Describe how antibodies are produced in the body following a viral infection (6 marks)

A
  • 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
25
Q

Explain one advantage of using antibodies from plants to treat diseases rather than antibodies produced in an experimental animal (1 mark)

A
  • Fewer ethical issues
    OR
  • Less risk of infection
26
Q

Explain why it’s important to use sterile techniques whilst culturing bacteria (2 marks)

A
  • To prevent contamination of apparatus with other bacteria

- To prevent release of bacteria into air

27
Q

Define monoclonal antibody (2 marks)

A
  • A clone of B-lymphocytes

- Formed from one type of plasma cell

28
Q

Suggest why it is necessary to give two injections of a vaccine (1 mark)

A
  • One dose doesn’t give enough antibodies to be effective
29
Q

Describe how T lymphocytes recognise and respond to the influenza virus (2 marks)

A
  • T lymphocyte receptors recognise the shape of the antigen
  • And stimulate the production of a clone of B-cells
  • To destroy the virus
30
Q

Explain how antigenic variability has caused some people to become infected more than once with the influenza virus (2 marks)

A
  • 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
31
Q

Describe the role of macrophages in stimulating B lymphocytes (1 mark)

A
  • Macrophages present the antigen in their membrane to the lymphocytes
32
Q

Describe how HIV is replicated after it has entered a human cell (4 marks)

A
  • 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
33
Q

Explain how the destruction of T-cells by HIV can lead to the death of an infected person (2 mark)

A
  • Not enough T-cells to activate B-cells

- So person is unable to fight opportunistic infections

34
Q

Explain what the clear zones around some of the discs containing antibiotic show in an experiment (2 marks)

A
  • Antibiotic has diffused into the agar

- And killed/inhibited bacteria

35
Q

Give two ways in which antibiotics can prevent bacterial growth (2 marks)

A
  • Disrupts cell wall

- Stops DNA replication

36
Q

Give two reasons why it’s important to use sterile techniques during an antibiotic investigation (2 marks)

A
  • To prevent contamination of apparatus with other microorganisms
  • To prevent release of bacteria into air
37
Q

Suggest why an effective antibiotic may produce only a small clear zone (1 mark)

A
  • It diffuses more slowly through the bacteria
38
Q

Describe the structure of a plasma membrane and explain how different substances are able to pass through the membrane by diffusion (6 marks)

A
  • 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
39
Q

Explain how antigenic variability has caused some people to become infected more than once with influenza viruses (2 marks)

A
  • Memory cells do not recognise new antigens

- So antibodies previously produced are not effective as the shape is not complementary to the new antigen

40
Q

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)

A
  • 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
41
Q

State the steps of the ELISA test (5 marks)

A
  • 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
42
Q

Define antibody (2 marks)

A
  • Protein
  • Specific to an antigen
  • Complementary shape
43
Q

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)

A
  • 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
44
Q

Suggest one reason why vaccinating a large number of people would reduce significantly the spread of HPV through the population (2 marks)

A
  • Virus cannot replicate / is destroyed / is not carried (in vaccinated people)
  • Non-vaccinated people more likely to contact vaccinated people
45
Q

Describe how B lymphocytes would respond to vaccination against viruses (4 marks)

A
  • 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

AQA AS Biology (14 decks)

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