20 8 Penicillin is an antibiotic. It was discovered in 1928. Since then many antibiotics have been identified and are widely used in the treatment of bacterial infections. (a) State what is meant by the term bacteriostatic antibiotic. (1) ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... (b) Scientists have recently discovered a new class of antibiotics that bind to ribosomes. (i) Explain why these antibiotics could affect the production of proteins in bacteria. 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Turn over 21 (ii) These new antibiotics attach to a site on the ribosome not affected by any known antibiotics. Deduce why these new antibiotics might be used to treat bacteria that are resistant to other antibiotics. (2) ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... *(iii) Scientists have isolated these new antibiotics and tested their effectiveness against bacteria that are resistant to other types of antibiotic. Devise a laboratory procedure to compare the effectiveness of penicillin with one of the new antibiotics. 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(Total for Question 8 = 12 marks) Turn over 23 BLANK PAGE