Penicillin is an antibiotic that prevents bacteria from synthesising cell walls. Long before penicillin became widely available in the 1940s, the enzyme penicillinase, which breaks down penicillin, had already been isolated. This enzyme is now present in many bacteria and makes them resistant to penicillin. Fig. 4.1 shows a ribbon model of the structure of the enzyme penicillinase. The arrow shows the enzyme’s active site.
(a)[3]
Explain why the shape of an enzyme’s active site, such as that of penicillinase, matters.
(b)[3]
With reference to Fig. 4.1, identify which aspects of protein structure are shown and which are not shown.
(c(i))[2]
Draw on Fig. 4.2 a curve to show the changes in energy during the progress of the same reaction when it is catalysed by an enzyme.
(c(ii))[1]
State the term used for the energy level that has to be overcome before a reaction can proceed.
(d)[2]
Antibiotic resistance is a serious worldwide problem. Suggest how antibiotics can be used effectively to avoid the development of widespread resistance in bacteria.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Substrate has complementary shape to active site” …