3 Infection and response higher (import)

Transcription

1 3 Infection and response higher (import) Name: Class: Date: Time: 38 minutes Marks: 38 marks Comments: Page of 3

2 A young child goes to school for the first time. Soon after, the child gets a cold and a sore throat. Explain, as fully as you can, what causes the child s illness. () (b) The doctor tells the child s mother that children often get ill when they start school and mix with other children. Why is a child more likely to get an infectious illness when he or she starts school? () (c) The child gets better without taking any medicine. Explain how. () (Total 4 marks) The table shows changes in resistance to the antibiotic penicillin in one species of bacterium between 99 and 996. Years Percentage of cases where bacteria were resistant to penicillin Page of 3

3 A doctor was asked to treat a patient who had a sore throat. (i) How does penicillin help to treat infection? () (ii) Use the data in the table to suggest why the doctor should not prescribe penicillin. () (Total 3 marks) 3 New drugs have to be thoroughly tested before they are sold. The diagram shows a time line for the testing of a new drug. What is the main purpose of pre-clinical testing? () (b) In Phase of the clinical testing, very low doses of the new drug are used on a small number of volunteers. (i) What is the main purpose of Phase testing? () Page 3 of 3

4 (ii) In Phase testing, healthy volunteers are used rather than patients. Suggest one reason for this () (c) What is the main purpose of the Phase and Phase 3 testing? () (d) During Phase 3 testing, many of the patients are given a placebo. (i) What is meant by a placebo? () (ii) During the testing, who knows which patients are receiving the placebo? Tick ( ) one box. Only the patients Only the doctors Both patients and doctors Neither patients nor doctors () (Total 6 marks) 4 Explain how diseases caused by bacteria are usually treated by doctors. () Page 4 of 3

5 (b) Explain, as fully as you can, how white blood cells protect us from disease. (5) (Total 7 marks) 5 Read the following passage. The immune system is the body s defence force. It protects against infections which might enter the body. The potential invaders include bacteria and viruses. The two basic defences are cells and chemicals. The best known action of defence cells is the ingesting and killing of microbes. The best known chemical defence is the antibody - a protein 5 specially made to match with the surface of an invading microbe. Once covered with antibody, the microbe becomes easier to destroy. So how do the invaders ever win? Part of the answer is that the chemical defenders take some time to become effective. When the body is infected for the first time by a particular microbe, there is a race between the multiplying microbes and the multiplying 0 cells producing the antibody. Given time, the body usually wins; eventually enough antibodies are formed to overcome the invaders. But if the initial invasion force is large, or the immune system is weak, the battle may be lost. (i) Which type of cells ingest and kill invading microbes? (lines 3-4) () Page 5 of 3

6 (ii) Give two circumstances in which the initial invasion force might be very large (lines - ) () (iii) After being ingested, the microbes are digested in the cells. Briefly explain what happens to the proteins that the microbes contain. () (b) Explain how bacteria cause disease once they get into the body. () (c) Name a type of medicine that kills bacteria inside the body. () Page 6 of 3

7 (d) People often risk first-time infection by a particular microbe while visiting other countries. People can be immunised against the disease that the microbe causes. Explain, as fully as you can, how immunisation works. (3) (Total marks) 6 Influenza is a disease caused by a virus. Explain why it is difficult to treat diseases caused by viruses. () Page 7 of 3

8 (b) In some years there are influenza epidemics. The graph shows the death rate in Liverpool during three influenza epidemics. (i) The population of Liverpool in 95 was approximately Calculate the approximate number of deaths from influenza in week 4 of the 95 epidemic. Show clearly how you work out your answer. Number of deaths... () Page 8 of 3

9 (ii) In most years, the number of deaths from influenza in Liverpool is very low. Explain, in terms of the influenza virus and the body s immune system, why there were large numbers of deaths in years such as 98 and 95. (3) (Total 7 marks) Page 9 of 3

10 Mark schemes microbes entered body, multiplied rapidly, made poisons any for mark each (b) contact with infected people for mark (c) the body kills the microbes for mark [4] (i) kills / destroys bacteria or prevents growth of bacteria do not allow germs do not allow fights or gets rid of (ii) any two from: bacteria may be resistant / immune (treatment futile) or bacteria would not be killed accept descriptions from table accept fights here do not accept people resistant may select for resistant type may cause increased incidence of resistance or Penicillin less effective in future sore throat might be due to a virus Penicillin would not work [3] 3 testing for toxicity / see if it is safe /see if it is dangerous / to see if it works ignore side effects unqualified Page 0 of 3

11 (b) (i) testing for side effects / testing for reactions (to drug) ignore to see if it works do not accept dosage (ii) any one from ignore immune system dose too low to help patient higher risk for patient might conflict with patient s treatment / patient on other drug (c) effect might be masked by patient s symptoms / side effects clearer to find optimum dose allow testing on larger sample or it makes results more reliable allow to find out if drug is effective /find out if drug works on ill people (not just if drug works) (d) (i) (tablet / drug / injection) that does not contain drug allow control / fake / false allow tablet / injection that does not affect body do not accept drug that does not affect body (ii) neither patients nor doctors [6] 4 use antibiotics; or named one to kill bacteria; (not microbes) each for mark (b) some ingest/digest bacteria (not microbes) OWTTE some produce antibodies; which destroy bacteria/viruses; some produce antitoxins; which counteract poisons released by bacteria each for mark 5 [7] Page of 3

12 5 (i) white blood cells for mark (ii) (iii) e.g. contact with infected person unhygienic conditions for mark each broken down, by enzymes into amino acids any for mark each (b) (c) (d) reproduce rapidly produce toxins antibiotic or named for mark each for mark mild or deal microbes introduced white cells produce antibodies which can destroy disease microbes idea of memory cells idea that injecting antibodies give immediate production any 3 for mark each 3 [] 6 any two from live inside / infect body cells difficult for drugs to enter (body) cells / drug would kill (body) cell antibiotics ineffective against viruses viruses mutate frequently (b) (i) 40 correct answer with or without working if answer incorrect evidence of number of deaths 7 or 60 seen gains mark ignore Page of 3

13 (ii) any three from: virus / flu mutates people no longer / not immune ignore resistance white blood cells / memory cells / immune system do not recognise virus relevant reference to antibodies / antigens current vaccine ineffective or no vaccine available then or takes time to develop new vaccine allow no tamiflu / anti-viral drugs conditions less hygienic / lack of hygiene people in poor health (following world wars) allow people had weak immune system 3 [7] Page 3 of 3