1. Revision Unit 4 Bacteria

21. January 2010

27. Sample Assessment Materials

37. A person suspected of being exposed to the Human Immunodeficiency Virus (HIV) may have their blood tested to check for infection. Some tests determine whether antibodies that act against the virus proteins are present in the blood. Explain how the presence of HIV proteins in the body results in the production of specific antibodies.

38. The graph below shows the change in the numbers of T helper cells in a person infected with HIV T helper cells are needed for all immune responses. Fewer than 200 cells per mm prevents an effective immune response.

39. T helper cells are needed for all immune responses. Fewer than 200 cells per mm prevents an effective immune response. Use the information in the graph to describe how HIV infection is likely to affect this individual’s health.

40. The graphs below show changes in the quantities of an antibiotic used in a hospital and the percentage of infections caused by bacteria resistant to the antibiotic over the same time period.

41. Using the information in the graph, explain how bacteria become resistant to antibiotics. Use the information in the graphs to support your answer.

42. Bacteria were grown on an agar plate and incubated with four different antibiotics. The antibiotics were placed on paper discs. The resulting plate is shown in the diagram below

43. Give one piece of evidence that suggests that antibiotic B is more effective at killing these bacteria than antibiotic C.

44. Antibiotic C is a much larger molecule than antibiotic B. Explain why this method might not be appropriate when comparing the effectiveness of antibiotics B and C.

45. Antibiotic C acts by inhibiting the growth of bacterial cell walls. Antibiotic D acts by interfering with the activity of bacterial ribosomes. Use this information to explain why neither antibiotic would be effective against viruses.