Turn over 13 5 Some antibiotics work by inhibiting the production of ribosomes in bacteria. The structure of ribosomes in bacteria is similar to the structure of ribosomes in mitochondria. (a) (i) Describe the structure of a ribosome. 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(ii) Describe the role of ribosomes in protein synthesis. 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The diagram shows the membranes of a mitochondrion from a cancer cell treated with these antibiotics. (i) Give one difference in the membranes of this mitochondrion compared with the membranes of a mitochondrion from an untreated cancer cell. (1) ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... (ii) Some cancer cells depend on oxidative phosphorylation for ATP production. Explain why the antibiotics that inhibit the production of ribosomes prevent oxidative phosphorylation when used to treat cancer cells. 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Turn over 15 (iii) Some scientists suggested that inhibiting both glycolysis and mitochondrial respiration may be an effective way of treating cancer cells. Explain why this suggestion may be an effective way of treating cancer cells. 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(Total for Question 5 = 9 marks)