Infection and Response

HIV (Human Immunodeficiency Virus) is a pathogen. How is HIV spread from one person to another person? Tick (✔) one box.

**Table 1** shows information about new cases of HIV diagnosed in the UK. Describe what happened to the number of new cases of HIV from 2010 to 2018.

What could cause a **decrease** in the number of new HIV cases in the future? Tick (✔) one box.

Scientists have been working to produce a vaccine for HIV for many years. How could a vaccine work to prevent a person being infected with HIV? Write the stages **A, B, C, D** and **E** in the correct order. The first stage has been completed for you. **A** Antibodies attach to the inactive virus. **B** Antibodies destroy the inactive virus. **C** An inactive form of the virus is injected into the body. **D** If the active virus enters the body, antibodies are produced quickly. **E** White blood cells produce antibodies to the inactive virus. C → ___ → ___ → ___ → ___

When scientists produce a vaccine for a disease the vaccine is tested on live animals. What is the next stage in testing the vaccine? Tick (✔) one box.

A vaccine for HIV is important because it is difficult to develop safe drugs to destroy viruses. Why is it difficult to develop safe drugs to destroy viruses? Tick (✔) one box.

Some drugs originated from plants. Which plant does the drug **Aspirin** originate from?

Some drugs originated from plants. Which plant does the drug **Digitalis** originate from?

Chemical A has not been tested in large-scale clinical trials in the UK. It is important for drugs to be tested in clinical trials before the drugs are approved for use by the public. Give two reasons why.

There are many online reports making claims about the effects of chemical A. Some of these reports are biased. Suggest one reason why a report making claims about the effects of chemical A may be biased.

How can scientists be sure that claims about new drugs are valid?

Salmonella bacteria cause outbreaks of food poisoning in humans. To prevent food poisoning in humans, farmers vaccinate their animals against Salmonella bacteria. How do Salmonella bacteria in food cause the symptoms of vomiting and diarrhoea?

During a food poisoning outbreak, scientists identified the farm where the food came from. The farmer had not vaccinated the farm animals against Salmonella bacteria. The food poisoning outbreak could have been prevented if the farm animals had been vaccinated. Explain how: • the immune systems of animals respond to a vaccination • the immune response in farm animals prevents an outbreak of food poisoning in humans.

Scientists investigated the effectiveness of five different antibiotics on the Salmonella bacteria in the outbreak. Antibiotics A, B, C, D and E were used in the investigation. Figure 4 shows the results. Describe two aseptic techniques the scientists should have used in the investigation.

The scientists incubated the bacteria at 37 °C. Students in school laboratories incubate bacteria at 25 °C. Explain why scientists use 37 °C but students must use 25 °C to incubate bacteria.

What is the purpose of the paper disc with no antibiotic in Figure 4?

The scientists concluded that either antibiotic A or antibiotic B should be prescribed to patients with food poisoning. Why should antibiotic A or antibiotic B be prescribed?

The scientists wanted to be more certain about which antibiotic should be prescribed. Describe how the results in Figure 4 could be used to obtain a quantitative comparison of antibiotics A and B.

One year later, there was another outbreak at the farm involving Salmonella bacteria. Antibiotic B did not have an effect. Suggest why antibiotic B no longer had an effect.

Antibiotics treat food poisoning because they kill Salmonella bacteria inside the human body. Some antibiotics work because they damage the bacterial cell wall. The bacteria die because the cells burst. Explain why the cells burst.

Scientists use monoclonal antibodies to test for the presence of anabolic steroids in an athlete's urine. To produce monoclonal antibodies, a mouse lymphocyte is combined with a tumour cell. What type of cell is created when a mouse lymphocyte and a tumour cell combine?

Describe how scientists make monoclonal antibodies using the cell created when a mouse lymphocyte and a tumour cell combine.

What property makes a monoclonal antibody useful in detecting the presence of an anabolic steroid in urine?

Figure 5 shows a test strip that can detect the presence of an anabolic steroid in an athlete's urine. The end of the test strip is dipped in urine. The urine moves up through the test strip. The test area and the control area contain a dye. The dye turns blue when monoclonal antibodies bind to it. Suggest the purpose of the control area in the test strip.

Figure 6 shows the urine test results of four athletes. Describe the evidence in Figure 6 that shows the test for athlete B has not worked. Suggest one reason why the test did not work.

Which athlete has tested positive for anabolic steroids in their urine?

The protist that causes malaria is passed from one person to another person by mosquitos. What term describes an organism that passes a pathogen from one person to another person?

Different types of disease may interact. Scientists studied the incidence of malaria infections in children: • with disorder S • without disorder S. The incidence of malaria in children with disorder S was calculated as a percentage of the incidence in children without disorder S. Table 4 shows the results. Describe what the results in Table 4 show about the interaction between disorder S and malaria.