Immunity etc T6 Flashcards
Cephalosporins are antibiotics that inhibit the production of bacterial cell walls.
Suggest why cephalosporins are bactericidal antibiotics.
(2)
- Death/killing of bacteria
- Since bacteria cells burst/loss of osmotic control.
Quinolones are antibiotics that inhibit the synthesis of DNA in bacterial cells.
Suggest why quinolones are bacteriostatic antibiotics.
(2)
- Cells cannot reproduce/multiply/replicate.
- No cell division/binary fission.
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 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.
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)
- 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.
Describe how macrophages ingest bacteria.
2
- Phagocytosis/engulfing.
- Membrane extends around bacteria/binds to bacteria.
- Bacterium inside vacuole/vesicle.
Suggest why treatment with antibiotics may not be effective against the dormant bacteria in
the tubercles.
(2)
- Bacteria need to be accessible to antibiotics.
- Bacteria are inside macrophages.
- Bacteria have waxy layer.
- Bacteriostatic antibiotics effect dividing bacteria.
- Bacteria antibiotic resistant.
TB can be prevented by vaccination. Explain how a person can develop artificial active
immunity following vaccination.
(2)
- 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.
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)
- 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.
Name the type of cell in the human immune
system that is infected by HIV.
T helper cell.
Name the enzyme used to produce DNA from viral
RNA in an infected cell.
Reverse transcriptase.
An antibody, known as 2G12, has been isolated from the blood of an HIV patient.
(i) State two characteristic features of antibodies.
(2)
- 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.
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)
- 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.
Suggest why data about HIV infections are often estimates.
2
- 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.
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)
- Skin epidermis is a barrier.
- Keratin in skin forms barrier.
- Lack of receptors for virus, skin has different receptors.
Suggest why common cold viruses cannot infect cells if they enter the blood through a cut in
the skin.
(2)
- Viruses only infect specific receptors.
- Receptors not present in blood cells.
- Destruction of virus by phagocytes.
