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Date May 2019 Marks available 2 Reference code 19M.3.HL.TZ2.10
Level Higher level Paper Paper 3 Time zone Time zone 2
Command term Outline Question number 10 Adapted from N/A

Question

The diagram shows the formation of a biofilm in a mammary gland, producing a mastitis infection.

[Source: © International Baccalaureate Organization 2019]

 

Outline the process of quorum sensing in bacteria forming a biofilm.

[2]
a.i.

Suggest one reason, other than quorum sensing, for the resistance to antibiotics of a biofilm.

[1]
a.ii.

Outline one example of an environmental problem caused by biofilms.

[2]
b.

Markscheme

a. cells/bacteria in a biofilm are close together ✔

b. cells secrete signaling molecules ✔

c. «signaling molecules» bind to receptors of other cells
OR
«signaling molecules» allow communication between cells ✔

d. a threshold is reached which enables emergent properties ✔

a.i.

a. polysaccharide matrix/EPS does not let antibiotic pass/limits transport of antibiotic ✔ OWTTE

b. reduced metabolic activity/growth rate of bacteria in biofilm contributes to resistance ✔

c. increased cell density limits transport of antibiotic «to the interior of biofilm» ✔

d. «horizontal» transfer of antibiotic resistance via plasmids ✔

a.ii.

a. area where biofilm problem exists ✔ eg emptying introduces invasive bacterial species into coastal waters.

b. environmental concern ✔

Allow other verified examples

b.

Examiners report

Most candidates seem to have a very good knowledge of biofilms, but it was more difficult to outline quorum sensing properly and suggest a reason for antibiotic resistance.

a.i.

Most candidates seem to have a very good knowledge of biofilms, but it was more difficult to outline quorum sensing properly and suggest a reason for antibiotic resistance.

a.ii.

Most could outline an example of biofilms but they had more difficulty relating it with an environmental concern.

b.

Syllabus sections

Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics) » B.3 Environmental protection
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