gce winter 2010 - question paper - KCSE Online

12
Examiner
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6. Penicillin and closely related biochemicals are widely used as antibiotics. Antibiotics vary in
their effectiveness depending upon the mode of action of the antibiotic and the organism that
is being targeted.
Drug companies conduct research to find the most effective antibiotic for use with particular
pathogens. In an investigation, the growth of four species of bacterium (K, L, M and N) was
observed without penicillin and with two different types of penicillin. Bacteria K and L are
Gram negative bacteria and M and N are Gram positive. Penicillin antibiotics act by
inhibiting the formation of crosslinks between certain molecules during cell wall synthesis.
The results of such an investigation are shown in the graph.
100
90
80
70
60
Growth / % 50
40
30
20
10
0
K L M N
Gram negative
Gram positive
Bacterium
No penicillin Penicillin Type 1 Penicillin Type 2
(a) (i) What was the purpose of growing bacteria in the absence of penicillin? [1]
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(ii)
Suggest which penicillin type should be prescribed for general use in patients
infected with any of these bacteria. [1]
.........................................................................................................................................................................................................
(iii) Which two species of bacteria are most affected by penicillin? [1]
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(314-01)