18 6 Acetyl CoA is produced in the link reaction when pyruvate is broken down. The photograph shows a molecule of the enzyme acetyl CoA carboxylase. This enzyme is involved in the conversion of acetyl CoA into fatty acids. The enzyme is activated by citrate. Citrate does not bind at the active site. Citrate is produced in the Krebs cycle. The enzyme is inhibited by long chain fatty acyl CoA molecules. Fatty acyl CoA molecules have a longer carbon chain than acetyl CoA. (a) (i) Analyse the information to explain how the activity of the enzyme acetyl CoA carboxylase is controlled. 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Turn over 19 .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) Explain why inhibitors of this enzyme may be useful in treating obesity in humans. 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(b) The enzyme acetyl CoA carboxylase has a different structure in bacteria. The enzyme in bacteria is made of several polypeptide subunits whereas in humans, the enzyme is one large polypeptide. Inhibitors of the bacterial enzyme are being developed to treat bacterial infections. Explain why inhibitors of the bacterial enzyme may be useful when treating bacterial infections. 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(Total for Question 6 = 9 marks)