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Question 19M.3.HL.TZ1.9a.ii

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Date May 2019 Marks available [Maximum mark: 1] Reference code 19M.3.HL.TZ1.9a.ii
Level HL Paper 3 Time zone TZ1
Command term Distinguish Question number a.ii Adapted from N/A
a.ii.
[Maximum mark: 1]
19M.3.HL.TZ1.9a.ii

Discs were soaked in different antibiotics and were placed on a culture of Bacillus subtilis spread on sterile agar in a Petri dish. The Petri dish was left in an incubator, after which zones of inhibition were observed surrounding some of the discs. The photograph is to scale.

[Source: Tasha L. Sturm. 2009. Kirby-Bauer disk diffusion susceptibility test. Visual Resources. American Society for
Microbiology, Washington, DC. www.microbelibrary.org Accessed 29 September 2014]

(a.ii)

Distinguish between the action of tetracycline and penicillin on B. subtilis.

[1]

Markscheme

tetracycline was more effective in inhibiting/killing the bacteria ✔

Examiners report

Students had no trouble identifying tetracycline as being more effective.

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