The specific immune response

Pathogens are transmitted to animals and plants by a variety of methods.

A group of scientists collected and analysed data about climate change and the number of cases of diseases transmitted by animal vectors.

The scientists wanted to know whether the number of cases of each disease had increased as a result of climate change.

They found that the number of cases had increased for 103 different animal vector‑transmitted diseases.

The scientists concluded that climate change has increased the transmission of pathogens by animal vectors.

Suggest one additional piece of information that is needed to assess the validity of the scientists’ conclusion.

Suggest why climate change might result in more cases of diseases caused by animal vector‑transmitted pathogens.

Neutrophils are white blood cells that contribute to the immune response against infection.

Neutrophils produce oxidative bursts as part of their response to infection.

An oxidative burst is the rapid production of highly reactive particles, including hydrogen peroxide (H₂O₂), inside the cell.

State the location of the stem cells that differentiate into neutrophils.

The graph shows the change in hydrogen peroxide concentration in a neutrophil during an oxidative burst.

Use the graph to calculate the initial rate of increase of H₂O₂ concentration in the neutrophil during an oxidative burst.

Suggest how an oxidative burst helps neutrophils to perform their function.

Antibodies can bind to receptors on the cell surface membrane of a neutrophil.

The binding of an antibody to a receptor causes the neutrophil to engulf the pathogen that is bound to the antibody.

State the name given to antibodies that act in this way.

Plants lack immune cells, but they have other defences against pathogenic infection.

The sentences describe one form of plant defence against pathogens.

Complete the sentences using the most appropriate word or phrase.

When a pathogen is detected in plant tissue, a plant increases the production of a

polysaccharide called........ This polysaccharide is deposited

in channels called........, which pass through cell walls. This

deposition stops the pathogen moving between cells. The polysaccharide is also

deposited in the small gaps between sieve tube elements. These gaps are known as

........ This deposition stops the pathogen moving between

different regions of the plant.

Vaccination can protect an individual from infectious disease.

Polio is a viral disease that usually affects children and can have lifelong effects.

A vaccine against polio was introduced in 1956.

Suggest the contents of the original anti-polio vaccine.

B-lymphocytes and T-lymphocytes are involved in the immune response.

Describe the role of T-lymphocytes in the development of immunity to a virus such as polio.

The graph shows the number of cases of polio in England and Wales between 1946 and 2016.

Calculate the percentage decrease in cases between 1956 and 1960.

A student wants to use the calculation in part (b)(i) to support a conclusion about the effectiveness of the polio vaccination. Another student argues that it would be better to have used 1957 as a starting year for the calculation.

Suggest two reasons why 1957 might have been a better starting year for the calculation.

There were cases of polio in England and Wales in the 1980s.

The scale used on the graph is not sensitive enough to show changes in the number of cases during the 1980s.

Suggest one way in which the y-axis scale could be changed in order that changes in the 1950s and 1980s were both visible.

Between 90% and 95% of UK children are currently fully vaccinated against polio.

In 2022 some particles of polio virus were detected in sewage in London. As a result, an extra dose of the polio vaccine was offered to children in London. The vaccine was not offered to children across the whole country.

Suggest why the extra vaccine was offered to children in London only.

Animals are protected from infectious diseases by their immune system.

Influenza is a viral disease that is common in winter months. It is transmitted when an uninfected person inhales droplets of moisture that an infected person has exhaled, often when coughing or sneezing.

Explain how mucous membranes make it more difficult for the influenza virus to enter the body.

Antigens on the surface of pathogens can provoke an immune response in a patient.

Fig. 19.1 shows the changes in antibody concentration in the blood of a patient.

Fig. 19.1

Different events during these immune responses have been represented as areas on the graph labelled with letters, A to F.

Complete the table with a letter or letters to indicate where on the graph the event is

Fragments of antibodies, known as Fab fragments, have a number of uses.

Snakebites can be treated using Fab fragments.

Antibodies specific to the snake venom are produced using donor animals, usually sheep. These antibodies are collected from the animal’s blood and then digested to produce Fab fragments. The patient can be injected with these fragments after being bitten by a snake.

Name the type of immunity this treatment gives the patient.

Fig. 19.2 shows the structure of a Fab fragment.

Fig. 19.2

Identify two similarities and one difference in structure between a Fab fragment and a whole antibody.

Infectious disease caused by pathogenic bacteria can be treated using antibiotics. The first antibiotics became widely available in the middle of the 20^th Century.

Explain why many varieties of pathogenic bacteria are now resistant to a range of antibiotics.

Plants and microorganisms have traditionally been used as sources of new medicines.

Synthetic biology could play a major role in the development of new medicines.

Outline how synthetic biology can be used in the provision of new medicines.

The heart can be affected by a variety of disorders, some of which involve the immune system.

Fig. 1.1 shows the roles of three different types of antibody, labelled R, S and T.

R S

Harmful molecules released by pathogens Fig. 1.1

State the names of the three different types of antibody shown in Fig. 1.1.

A condition called rheumatic heart disease can occur when a person’s antibodies attack antigens on their own heart cells.

State the name of the type of disease represented by rheumatic heart disease.

Fig. 1.2 shows two electrocardiogram (ECG) traces:

• an ECG of normal heart activity

• an ECG of a person with a type of heart disease

Fig. 1.2

Describe how the ECG trace of the heart with heart disease is different from the ECG trace of a normal heart.

Gene therapy is a possible future treatment for heart disease.

The AC6 gene codes for one form of the enzyme adenylyl cyclase.

Clinical trials have tested the effect of increasing levels of the AC6 gene in heart cells.

Suggest how using gene therapy to increase levels of the AC6 gene in heart cells may improve heart function.

State one method for inserting the AC6 gene into the heart cells during gene therapy.

The results from gene therapy trials are published in peer-reviewed journals.

State why the results from gene therapy trials are published in journals.

Which of the following is/are not involved in the primary response against infection?

A memory B-cells

B mast cells

C mitosis

D platelets

Your answer

It is possible to manufacture antibodies to treat certain diseases. These are known as synthetic antibodies.

DNL-Fab3, shown in Fig. 4.2, is an example of a synthetic antibody.

State two conclusions that can be drawn from Fig. 4.2 about the differences between the way DNL-Fab3 functions and the functioning of normal antibodies.

Agammaglobulinemia and Vici syndrome are both genetic diseases.

Agammaglobulinemia results in a lack of mature B lymphocytes in a person’s blood.

Suggest and explain one symptom of agammaglobulinemia.

Fig. 4 shows the inheritance pattern of agammaglobulinemia in a family.

What conclusions can you draw about the location and nature of the allele responsible for causing agammaglobulinemia? Explain your conclusions.

Vici syndrome is a genetic disease that shows a recessive inheritance pattern. The allele responsible for Vici syndrome is found on chromosome 18.

Two carriers of Vici syndrome have six children.

Calculate how many of the six children you would expect to:

• have Vici syndrome

• be carriers of Vici syndrome.

A daughter of these parents and a male carrier of Vici syndrome have a child.

Calculate the probability of the child having Vici syndrome.

DNA profiling can be used to analyse the risk of inheriting conditions such as agammaglobulinemia and Vici syndrome.

To produce a DNA profile, DNA first needs to be purified.

Explain why a protease enzyme is added to the mixture during the DNA purification process.

DNA samples can be amplified using the polymerase chain reaction (PCR).

In theory, how many fragments of DNA might be present after 12 cycles of PCR?

Assume one DNA fragment was present at the beginning of the PCR process. Represent your answer as a log₁₀ value.

Suggest why the figure you calculated in (ii) may not be achieved in practice.

State the name of the enzyme used in PCR to synthesise new DNA strands.

DNA fragments are separated to produce a DNA profile using electrophoresis.

A student wrote the following description of the electrophoresis procedure:

We will set up an agarose gel plate and place the DNA samples in the wells at the cathode. Voltage will be passed through the gel for one minute. The gel will then be placed in purified water and we will be able to see the banding pattern of each DNA sample.

Describe two changes you would make to the student’s procedure and explain how these changes would improve electrophoresis.

Bread contains a mixture of polypeptides known as gluten.

Gluten consists of two types of polypeptide: gliadins and glutenins.

The table below contains statements about the structures of gluten polypeptides.

In the boxes next to each statement, write the level of protein structure (primary, secondary, tertiary, or quaternary) to which the statement refers.

Coeliac disease is caused by an immune reaction to gliadins in a person’s digestive system. The immune system produces antibodies that bind to part of the gliadin polypeptides, which causes inflammation.

Some people who stop eating foods that contain gluten still occasionally experience the symptoms of coeliac disease.

What can you conclude about:

• the structure of the antibody that causes coeliac disease; and

• what the antibody binds to when producing the symptoms of coeliac disease?

Gluten helps to trap carbon dioxide within bread dough. This enables bread to rise when it is baked.

The carbon dioxide is produced by baker’s yeast, Saccharomyces cerevisiae. This species of yeast is able to convert ethanol to acetyl CoA at low glucose concentrations.

Fig. 2 shows the oxygen consumption and carbon dioxide production of a population of S. cerevisiae grown in batch culture. The population was provided with glucose as their only initial source of carbon.

Fig. 2

Suggest and explain what conclusions can be drawn from Fig. 2 about the factors that affected the rate and type of respiration carried out by S. cerevisiae in this batch culture.

Describe two practical considerations to ensure the S. cerevisiae population grows successfully when the initial culture is established.

A group of students were designing an experiment to investigate the effect of temperature on the respiration rate of S. cerevisiae.

Their planned method included the following:

• S. cerevisiae yeast suspension will be divided into six equal volumes to form the experimental groups.

• Six temperatures will be tested: 15 °C, 20 °C, 25 °C, 30 °C, 35 °C and 40 °C.

• Beakers of S. cerevisiae will be placed in water baths to control the temperature.

• Respiration rate will be measured by using a pH probe to monitor changes in the pH of the suspensions.

• The experiment will be repeated four times.

Evaluate whether the students’ method is likely to produce valid results.

The students used a Student’s t-test to compare the results at 30 °C and 35 °C.

They calculated a t value of 2.200.

The critical value for p = 0.05 is 2.306.

Assuming their final method was valid, what can the students conclude from the result of the t-test?