Synoptic Exam Questions (Section C) (Edexcel International A Level (IAL) Biology): Exam Questions

Mycobacterium tuberculosis is a pathogenic bacterium that infects the lungs, causing tuberculosis (TB).

The diagram shows a representation of an M. tuberculosis cell.

(i) Identify structures X and Y.

[2]

(ii) The length of the cell in the diagram is 8.8 cm. The diagram is magnified 25 000 times.

Calculate the actual length of the M. tuberculosis cell shown. Give your answer in μm.

[2]

M. tuberculosis evades the host immune system by infecting and surviving inside macrophages.

A patient infected with M. tuberculosis was monitored over a four-week period. Blood tests showed sustained high concentrations of specific antibodies, but the number of bacteria in the patient's lungs continued to increase.

Suggest why the production of antibodies alone is not sufficient to clear a Mycobacterium tuberculosis infection.

Scientists extracted DNA from M. tuberculosis samples and used PCR followed by gel electrophoresis to compare the genomes of antibiotic resistant and non-resistant strains.

Explain why PCR was carried out on the DNA samples before gel electrophoresis.

Describe the process of gel electrophoresis used to compare the genomes.

Antibiotic resistance in M. tuberculosis is a growing problem worldwide, making some TB infections difficult to treat.

Explain how antibiotic-resistant strains of M. tuberculosis can develop.

The scientific document (opens in a new tab) you have studied is adapted from an article in Science Direct: Assessment of food toxicology by Alexander Gosslau.

Use the information from the scientific article and your own knowledge to answer the following questions.

Explain how toxicants in food could cause Parkinson’s disease (paragraph 3).

Suggest how the genes affected by toxicants can be identified (paragraph 4).

Explain how scientists could determine the high degree of homology of genes between humans and zebrafish (paragraph 5).

Suggest how electrophilic species (ES) of free radicals could be “involved in the modulation of gene expression” (paragraph 6).

Suggest how ES can damage mtDNA (paragraph 7).

In the MTT assay, reduced NAD converts an MTT solution from yellow to purple.

Describe how the MTT assay could be used to show which of two drugs is more toxic to cells (paragraph 10).

Explain the advantages of reprogramming ordinary somatic cells to behave like embryonic stem cells for use in stem cell‐based assays of toxicants (paragraph 11).

The scientific article (opens in a new tab) you have studied is adapted from Rethinking Alzheimer’s in New Scientist (February 2019).

Use the information from the scientific article and your own knowledge to answer the following questions.

Memory and cognitive function are two processes that occur in the brain (paragraphs 2 and 13).

Different parts of the brain are responsible for specific functions.

Complete the table showing which parts of the brain are responsible for different functions.

Some forms of dementia can be diagnosed using brain scans.

Compare and contrast the use of functional magnetic resonance imaging (fMRI) and computed tomography (CT) scans to identify structures like plaques in the brain (paragraph 6).

Suggest how the amyloid protein may prevent bacterial infection in the brain (paragraphs 7 and 22).

Explain how the bacterium Porphyromonas gingivalis that causes gum disease may invade the brain and cause inflammation in brain regions affected by Alzheimer’s disease (paragraphs 10, 20 and 21).

Suggest how gingipains may have a degrading effect on the memory of a person suffering from Alzheimer’s disease (paragraph 12).

The team found genetic material from P. gingivalis in the cerebral cortex (paragraph 13).

Describe how the team could show that this genetic material is active.

Cystic fibrosis (CF) is caused by a mutation in the gene encoding the CFTR protein. The mutation changes one base in the normal CFTR sequence from CCT to CGT.

Name the type of mutation that occurs.

The mutated CFTR gene contains the following DNA sequence:

TAC — GGA — CGT — ATG

Determine the amino acid sequence transcribed from this DNA.

Use the table below.

People with cystic fibrosis produce very thick, sticky mucus

Explain why a mutation in this gene results in the production of very thick, sticky mucus.

The thick mucus accumulates in the airways of the lungs.

Which of the following explains why thick mucus reduces gaseous exchange?

A couple are both unaffected carriers of cystic fibrosis.

Construct a genetic cross and determine the probability of their next child being a carrier.

When activated, T lymphocytes can divide rapidly and secrete proteins called cytokines.

These cytokines will activate different types of lymphocyte.

(i) Which is the function of tRNA in cytokine synthesis?

(1)

(ii) Which organelle is involved in chemically modifying cytokine proteins before they are secreted?

(1)

Describe the role of DNA polymerase in DNA replication during cell proliferation.

Explain how cytokine genes can be expressed in an activated T lymphocyte.

CD45 is a protein found on the surface of lymphocytes. Different forms of the CD45 protein are found on the surface of different lymphocytes.

Describe how different forms of the CD45 protein can be produced from a single CD45 gene.

Female mosquitoes feed on the blood of other animals to promote the development of their eggs. During this process, infected mosquitoes can transmit the Plasmodium parasite.

The Plasmodium parasite causes the disease malaria.

The photograph shows a female Anopheles mosquito.

A ruler has been included for scale. 

Alan R Walker, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Calculate the magnification of the Anopheles mosquito in this photograph.

Give your answer to one decimal place.

In 2017, an estimated 219 million people in 87 countries had malaria, and 435 000 of these people died.

Which of the following shows the percentage of infected people who died?

☐ A 0.02%
☐ B 0.20%
☐ C 99.80%
☐ D 99.98%

The fungus Metarhizium pingshaense infects Anopheles mosquitoes.

A student drew a labelled diagram of a fungal cell that was dividing.

(i) State the function of a nucleolus.

(1)

(ii) Give three differences in ultrastructure between this cell and a cell taken from the root of a plant.

(3)

Insecticides are chemicals used to kill insects.

Anopheles mosquitoes have developed resistance to the insecticides currently used.

Metarhizium pingshaense is a fungus that infects Anopheles mosquitoes.

Scientists in West Africa have genetically engineered (GE) this fungus using a gene from a spider.

When the GE fungus infects an Anopheles mosquito this gene becomes activated. A toxin is released, which kills the mosquito.

In an investigation, four huts each containing a group of 500 breeding pairs of mosquitoes were used.

Three different treatments used to kill mosquitoes were compared with a control group.

The walls and ceiling of the huts were sprayed with the treatment.

The table shows the number of adult mosquitoes in the first two generations of offspring from each hut after spraying.

Evaluate these three treatments.

Use the information in the question, and your own knowledge, to support your answer.

The scientific document (opens in a new tab) you have studied is adapted from an article in Education in Chemistry: Developing vaccines, Self-defence classes for our immune system.

Use the information from the scientific document and your own knowledge to answer the following questions.

The Ebola virus can infect endothelial cells.

Describe how this virus can cause internal bleeding (paragraph 1).

Explain how ‘our immune systems learn to make another type of protein, called an antibody’ (paragraph 4).

One method of slowing the degradation of vaccine proteins is to dry a mixture of sugars and vaccine on a filter.

Explain why flushing with water releases the vaccine from the filter (paragraphs 8 and 9).

During the production of some vaccines, the virus is allowed to replicate in eggs (paragraph 13).

Explain how a vaccine produced in this way may become less effective.

Scientists are using genetically modified bacteria and insect cells to produce the antigens for Ebola vaccines (paragraph 13).

(i) Describe how insect cells could be genetically modified to produce the antigens for an Ebola vaccine. 

(4)

(ii) Suggest three benefits of using an insect cell to produce the Ebola virus antigen.

(3)

Suggest why the stems of the different versions of haemagglutinin molecules are the same but the heads can be different (paragraph 15).

The scientific document (opens in a new tab) you have studied is adapted from an article in Journal of Cachexia, Sarcopenia and Muscle entitled Skeletal muscle performance and ageing. (Tieland, 2018).

Use the information from the scientific document and your own knowledge to answer the following questions.

Describe the structure of a skeletal muscle fibre (paragraph 2).

Explain how myokines may exert endocrine effects on organs such as the liver (paragraph 3).

Explain why the changes that occur to muscle structure and composition in the elderly can affect their ability to rise from a chair (paragraph 4).

Explain why Ca²⁺ binding to troponin C allows muscle fibres to contract (paragraph 5).

Explain how the ‘high-energy phosphates’ provide the energy necessary for muscle activity (paragraph 11).

Suggest explanations for the effects that a ‘reduction in tendon stiffness’ resulting from ageing could have on the movement at a joint (paragraph 12).

Suggest how myostatin might act as a negative regulator of muscle growth (paragraph 13).