gce winter 2010 - question paper - KCSE Online

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12 Examiner only 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] ......................................................................................................................................................................................................... (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] ......................................................................................................................................................................................................... (314-01)
13 Examiner only (iv) Using the information given and your own knowledge, suggest why the various species of bacteria respond differently to penicillin. [2] ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... (b) The bacteria infecting humans will be found in the blood or tissue fluid. (i) Using the information given and your knowledge, explain the mechanism by which penicillin brings about the destruction of bacterial cells. [3] ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... ......................................................................................................................................................................................................... (ii) When might the bacteria be most susceptible to the action of penicillin? [1] ......................................................................................................................................................................................................... (Total 9 marks) (314-01) Turn over.
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gce winter 2010 - question paper - KCSE Online

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