Physical and chemical barriers

Blood contains different types of cell.

Complete the sentences.

Choose answers from the box.

White blood cells defend the body against

Some white blood cells release chemicals that neutralise toxins. These chemicals

Figure 3 shows a white blood cell.

The image of the white blood cell in Figure 3 is magnified 4000 times.

Calculate the real width of the white blood cell.

Complete the following steps.

Measure width W in millimetres (mm).

Convert your measurement to micrometres (µm).

1 millimetre (mm) = 1000 micrometres (µm).

Calculate the real width of the white blood cell.

Use the equation:

Table 3 shows information about different types of blood vessel.

The width of a red blood cell is 8 µm.

Figure 4 shows red blood cells in one type of blood vessel.

Which type of blood vessel is shown in Figure 4 ?

Use Table 3.

Tick () one box.

Explain why arteries need to have thick walls.

Use Table 3.

Coronary arteries in the heart can become narrowed.

What happens inside coronary arteries to cause them to become narrowed?

Explain why narrowed coronary arteries can be dangerous.

Treatments are available for some cardiovascular diseases.

Draw one line from each cardiovascular disease to a treatment for the disease.

Why is coronary heart disease described as a ‘non-communicable disease’?

Pathogens cause disease.

How does the skin defend the human body against pathogens?

The stomach contains acid to kill pathogens.

A scientist investigated the effect of acid on the survival of bacteria.

This is the method used.

1. Prepare four test tubes each with 10 cm³ of culture solution.

2. Use acid to adjust the pH of the solutions to be pH1, pH2, pH3 and pH5

3. Add 1 cm³ of bacteria mixture to each test tube.

4. Take a 0.1 cm³ sample from each test tube and record the number of live bacteria.

5. Keep the test tubes at 37 °C for 24 hours.

6. Repeat step 4.

Table 1 shows some of the results.

What fraction of the bacteria present at 0 hours for pH3 survived for 24 hours?

Give your answer in its simplest form.

Fraction surviving =

How many more bacteria were killed at pH1 than at pH5 in 24 hours?

Complete the following steps.

A student calculated value X in Table 1 to be 43

Suggest how the student calculated this value.

Viruses cause disease.

What name is given to microorganisms that cause disease?

Tick (✓) one box.

The body has defences to stop viruses entering.

Draw one line from each defence to the part of the body that provides the defence.

Part of the body that

Some viruses can cause tumours to develop.

Complete the sentence.

Choose the answer from the box.

A tumour can form when changes to cells cause uncontrolled

cell.

Malignant tumours are cancers.

Which two sentences describe malignant tumours?

Tick (✓) two boxes.

HPV is a virus that can cause one type of cancer in females.

In the UK since 2008, most 12 to 13-year-old females have been vaccinated against HPV.

Scientists investigated the percentage of 16 to 18-year-old females with HPV.

Table 2 shows the results.

What does Table 2 show about the percentage of females with HPV from 2010 to 2016?

Suggest the reason for the change you described in Question 02.5.

The HPV vaccine contains an inactive form of the virus.

The inactive form of the virus is injected into the body.

Which part of the blood responds to the inactive virus?

Tick (✓) one box.

What is produced by the body in response to the inactive virus?

Tick (✓) one box.

Suggest one reason why some parents refuse to allow their children to have the HPV vaccine.

Do not refer to the pain of the injection in your answer.

The human body can defend itself against microorganisms that cause disease. Viruses are one type of microorganism that cause disease.

Name one type of microorganism that causes disease in humans. Do not refer to viruses in your answer.

Which two defence systems prevent microorganisms infecting the human body? Tick (✓) two boxes.

If microorganisms enter the human body the immune system can destroy the microorganisms. How does the immune system destroy microorganisms? Tick (✓) one box.

Vaccinations prevent people becoming ill with diseases such as measles. Complete the sentences. Choose answers from the box.

If the measles virus enters the body after vaccination the immune system reaction

How is the measles virus spread from one person to another?

Doctors investigated the spread of the virus that causes chickenpox.

The first symptom of chickenpox after exposure to the virus is spots on the body. 23 children were playing together at a party. On the day of the party one of the children developed chickenpox spots. Every two days after the party, the doctors recorded when the other 22 children first showed chickenpox spots. Table 1 shows the results.

What was the range for the days on which children first showed chickenpox spots? Use Table 1.

Incubation time is the usual time from exposure to a pathogen until the first symptoms appear. Suggest the most likely incubation time for chickenpox.

Suggest one reason why some of the children did not develop chickenpox.

One mother gave antibiotics to her child who had chickenpox. Suggest why this child did not recover more quickly than the other children who had chickenpox.

Monoclonal antibodies (mAbs) are usually made using mouse lymphocytes. Candida albicans infection produces serious symptoms in patients with a poor immune system. Recently scientists have produced mAbs to Candida albicans using human lymphocytes produced naturally after an infection.

Candida albicans lives in the throat of infected patients. A sample is taken from the throat of a patient with a suspected Candida albicans infection. The sample is transferred onto a microscope slide. Describe how the mAbs and a fluorescent dye could be used to see any Candida albicans pathogens on the slide.

In a laboratory the human lymphocyte mAbs were injected into animals infected

with Candida albicans. The mAbs caused increased phagocytosis of the Candida albicans pathogens. Doctors intend to start a trial to give the mAbs to patients severely ill with Candida albicans.

Explain how increased phagocytosis of the Candida albicans pathogen will help the patient.

It has been shown that this mAbs treatment is effective in the laboratory using both:

• infected tissue culture cells

• infected live animals.

The mAbs treatment for Candida albicans is now ready for clinical trials on people. Describe how the clinical trials should be carried out.

Scientists have also used human lymphocytes to make mAbs to other pathogens and to some types of cancer cells. Suggest one reason why these new mAbs have been more successful in treating diseases in humans than mAbs made using mice.

Mosquitoes carry a pathogen that causes malaria.

What type of pathogen causes malaria?

Tick (✓) one box.

Mosquito nets can help prevent the spread of malaria.

Table 7 shows the results of a study in one area of Africa.

A newspaper made the following statement:

‘Study shows mosquito nets are scientifically proven to prevent malaria.’

Give one piece of evidence that supports the statement.

Suggest one reason why the statement may not be valid.

Table 8 shows information about the number of deaths from malaria in the same area of Africa.

Predict the number of people per 100 000 who died from malaria in 2017 if the trend stayed the same.

Use of mosquito nets has helped to reduce the number of deaths from malaria each year.

Suggest one other reason for the reduced number of deaths from malaria each year.

Describe how the human body:

• prevents pathogens from entering

• defends itself against pathogens inside the body.

Mosquitoes carry a pathogen that causes malaria.

What type of pathogen causes malaria?

Tick (✓) one box.

Mosquito nets can help prevent the spread of malaria.

Table 1 shows the results of a study in one area of Africa.

A newspaper made the following statement:

‘Study shows mosquito nets are scientifically proven to prevent malaria.’

Give one piece of evidence that supports the statement.

Suggest one reason why the statement may not be valid.

Table 2 shows information about the number of deaths from malaria in the same area of Africa.

Predict the number of people per 100 000 who died from malaria in 2017 if the trend stayed the same.

Use of mosquito nets has helped to reduce the number of deaths from malaria each year.

Suggest one other reason for the reduced number of deaths from malaria each year.

Describe how the human body:

• prevents pathogens from entering

• defends itself against pathogens inside the body.