Immunity etc T6 Flashcards

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1
Q

Cephalosporins are antibiotics that inhibit the production of bacterial cell walls.
Suggest why cephalosporins are bactericidal antibiotics.
(2)

A
  • Death/killing of bacteria

- Since bacteria cells burst/loss of osmotic control.

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2
Q

Quinolones are antibiotics that inhibit the synthesis of DNA in bacterial cells.
Suggest why quinolones are bacteriostatic antibiotics.
(2)

A
  • Cells cannot reproduce/multiply/replicate.

- No cell division/binary fission.

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3
Q

After incubation, the scientists in the laboratory concluded that C. difficile was completely
resistant to antibiotics A and C. They also concluded that antibiotic D was more effective against C. difficile than antibiotic B.
(i) Explain how the appearance of the nutrient agar plates, after incubation, would have enabled
the scientists to reach these conclusions.
(3)

A
  • A and C resistant as no clear zone/zone of inhibition around A and C.
  • Clear zone indicates where antibiotic inhibits growth/kills bacteria.
  • Size and diameter of clear zone indicates effectiveness.
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4
Q

Human diseases can be caused by many different types of organism, such as bacteria
and viruses.
(a) Give two differences between the genetic material of bacteria and viruses.
(2)

A
  • Bacteria have DNA
  • Viruses have RNA or DNA.
  • Bacteria have circular DNA, viruses have linear.
  • Bacteria DNA is double stranded, virus RNA is single stranded.
  • Bacteria have plasmids, viruses do not.
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5
Q

Describe how macrophages ingest bacteria.

2

A
  • Phagocytosis/engulfing.
  • Membrane extends around bacteria/binds to bacteria.
  • Bacterium inside vacuole/vesicle.
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6
Q

Suggest why treatment with antibiotics may not be effective against the dormant bacteria in
the tubercles.
(2)

A
  • Bacteria need to be accessible to antibiotics.
  • Bacteria are inside macrophages.
  • Bacteria have waxy layer.
  • Bacteriostatic antibiotics effect dividing bacteria.
  • Bacteria antibiotic resistant.
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7
Q

TB can be prevented by vaccination. Explain how a person can develop artificial active
immunity following vaccination.
(2)

A
  • Dead pathogen put into person.
  • Stimulation of specific/primary immune response.
  • T helper cell activation from APC macrophages.
  • B cell activation by cytokines, B cells as APC.
  • T killer cell activation by cytokines.
  • Production of T and B memory cells.
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8
Q

In a person with TB, the dormant bacteria in tubercles may be activated after several years.
The bacteria multiply rapidly, resulting in severe lung damage.
The bacteria are released from the tubercles. These bacteria can inhibit the activity of T cells
and infect other organs.
Explain why the activity of these bacteria and the inhibition of T cells means that a person may
quickly develop severe symptoms leading to death.
(4)

A
  • Further lung damage/severe breathing problems.
  • Mycobacterium get into blood/lymph.
  • Organ failure leads to death.
  • Reduced/weakened immune response due to loss of T cells.
  • T helper cells produce cytokines.
  • T killer cells not activated so infected cells not destroyed.
  • B cells not activated, no antibodies produced.
  • Secondary and opportunistic infections causing death.
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9
Q

Name the type of cell in the human immune

system that is infected by HIV.

A

T helper cell.

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10
Q

Name the enzyme used to produce DNA from viral

RNA in an infected cell.

A

Reverse transcriptase.

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11
Q

An antibody, known as 2G12, has been isolated from the blood of an HIV patient.
(i) State two characteristic features of antibodies.
(2)

A
  • Chain of amino acids.
  • Disulphide bridges between peptides.
  • Y shaped drawing.
  • Antigen binding site.
  • Antibodies have a similar region.
  • Produced by plasma cells.
  • Causes lysis.
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12
Q

The antibody 2G12 is produced in response to part of a glycoprotein found on the surface of
HIV. Synthetic molecules have been made that resemble this part of the glycoprotein. The
antibody 2G12 binds to these synthetic molecules.
Using the information, suggest how this may enable scientists to develop a means of producing
active immunity to HIV infection.
(5)

A
  • Artificial active immunity.
  • Vaccination.
  • Containing synthetic molecule glycoprotein.
  • Stimulation of specific immune response to synthetic antigen.
  • Clonal expansion of B cells.
  • Cytokines activation of t killer cells and b effector cells.
  • T helper cells activate B cells.
  • Production of B memory cells.
  • 2G12 antibodies are produced faster on reinfection.
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13
Q

Suggest why data about HIV infections are often estimates.

2

A
  • HIV infection does not always produce symptoms.
  • HIV virus may be dormant.
  • Test needed to detect symptomless HIV.
  • Only those who suspect they have HIV will get tested.
  • Some people don’t want to be tested.
  • HIV symptoms common to other diseases.
  • New cases arise and patients die at same time.
  • New strains of virus arising.
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14
Q

Common cold viruses infect only the cells inside the nose.
(i) Suggest why common cold viruses cannot infect cells if they land on unbroken skin.
(2)

A
  • Skin epidermis is a barrier.
  • Keratin in skin forms barrier.
  • Lack of receptors for virus, skin has different receptors.
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15
Q

Suggest why common cold viruses cannot infect cells if they enter the blood through a cut in
the skin.
(2)

A
  • Viruses only infect specific receptors.
  • Receptors not present in blood cells.
  • Destruction of virus by phagocytes.
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16
Q

Human papilloma virus (HPV) is a DNA virus.
Cervarix and Guardasil have been used in national vaccination programs.
A person who has been vaccinated becomes infected with HPV-16. Explain the role of the T cells
in the body of this person.
(3)

A
  • A vaccinated person will have T memory cells.
  • T memory cells recognise antigens specific to HPV-16 virus.
  • T helper cells activate B cells/T killer cells.
  • Formation of t killer cells which destroy virus infected host cells.
17
Q

Histamine and the proteins interferon and lysozyme are involved in the non-specific responses to
infection.
(a) (i) Describe how the production and action of interferon differs from the production and
action of lysozyme.
(3)

A
  • interferon involved in viral infections. Lysozyme affects bacteria.
  • Interferon produced by infected cells. Lysozyme present in phagocytes/macrophages.
  • Interferon inhibits replication of viruses. Lysozyme kills/destroys bacteria.
18
Q

Suggest why the protein structure of lysozyme is important to the way in which it acts
against pathogens.
(4)

A
  • Lysozyme is an enzyme.
  • Enzyme active site have specific shape.
  • Lysozyme acts on cell wall.
  • Cell wall of bacteria.
19
Q

Following a bite by an insect, the area around the bite may show signs of inflammation as
histamine is released.
(i) Explain why an insect bite, which breaks the surface of the skin, may lead to inflammation
around the injury.
(3)

A
  • Histamine released as a result of damaged tissue/cells.
  • Histamine released from platelets.
  • Histamine causes arterioles to dilate/vasodilation. Makes capillaries more permeable.
  • Causes swelling/oedema/redness/heat/pain.
20
Q

In order to reduce inflammation, a cream containing antihistamines might be applied to the
skin, around an insect bite.
Suggest why applying this cream might be better than taking tablets containing antihistamines.
(3)

A
  • Histamines produced around bite area.
  • Cream has been applied to actual site of histamine production.
  • Treatment therefore more rapid.
  • Higher concentration of antihistamine at site.
  • Antihistamines will not be digested by enzymes or destroyed by acid.
  • Tablets may lower immune response generally/side effects.
21
Q

One role of the skin is to protect the body from infection.
(i) Explain how skin flora protect the body from infection.
(2)

A
  • Skin flora prevent growth of pathogens/microorganisms.
  • Competition for space/nutrients/water/minerals.
  • Release of chemicals/toxins/enzymes/antimicrobials.
22
Q

The skin produces lipids that protect the body from infection, explain how these protect the body from infection.

A

-The lipids have antimicrobial properties that inhibit bacteria growth.

23
Q

Some of the blood plasma of individuals who have survived infection with Ebola can be
collected. This can be used in the treatment of individuals currently infected with Ebola.
Explain why the blood plasma from survivors can be used to treat new cases of Ebola infection.
(3)

A
  • Survivors will have antibodies specific to the virus in their plasma.
  • Antibodies given to individuals infected will provide passive immunity.
  • The antibodies provided will therefore opsonise the virus particles.
24
Q

(c) A study of the 2014 Ebola outbreak in Sierra Leone found that the Ebola virus was evolving
rapidly.
Explain why the evolution of the virus might reduce the effectiveness of any vaccine being
developed.
(4)

A
  • Vaccine stimulates immune response to make antibodies specific to viral proteins.
  • Mutations in the viral nucleic acid
  • results in a change in the shape of viral proteins.
  • Therefore antibodies can no longer bind to virus.