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Aitchison College Academic Resources.
2. Antibiotics are used to treat human diseases.
Many bacteria have become resistant to antibiotics. Some antibiotics can no longer be used
to treat certain diseases.
Samples of bacteria were taken from a person who had an infectious disease. They were
spread onto four Petri dishes of agar (agar plates). Three of these agar plates contained the
antibiotics 1, 2 or 3.
The results are shown in Fig. 2.1.
Oo0@
agar plate contains agar plate contains agar plate contains agar plate contains
no antibiotic antibiotic 1 antibiotic 2 antibiotic 3
key
[By bacterial growth
[_] no bacteria
Fig. 2.1
(a) Explain why:
(i) no bacteria grew in the agar plate with antibiotic 2;
[1]
(ii) bacteria grew in the agar plate with antibiotic 3;
(1]
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