gcseprep.com · web viewtopic 2 – cells, viruses and reproduction of living things. q1. the...

Topic 2 – Cells, Viruses and Reproduction of Living Things

Q1.

The resistance of one type of bacteria to a range of different antibiotics was investigated.

A lawn of bacteria was prepared by spreading a suspension of the bacteria over the surface of agar. Paper discs that had been soaked previously in different antibiotics were placed on top of the bacteria. The antibiotics were all the same concentration. The culture was incubated for 48 hours.

The diagram below shows the appearance of the culture after incubation.

Explain why these results indicate that the bacteria must be Gram positive.

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(Total for question = 3 marks)

Q2.

A student read that more than half of raw chickens on sale in supermarkets are contaminated with bacteria from the genus Campylobacter.

Some species of Campylobacter cause food poisoning in humans.

The student carried out an experiment to test the effectiveness of various antibiotics against Campylobacter.

The photograph shows the student's agar plates at the end of the experiment.

The white circles labelled A–H are filter paper discs. These discs were soaked in different antibiotics then placed on the surface of the agar.

One of the antibiotics the student used was penicillin. Describe the effect of penicillin on bacterial cells.

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Q3.

A scientist separated the components of animal cells using density gradient centrifugation.

The density gradient is made by layering sucrose solutions of different density on top of each other in a tube, as shown in the diagram.

The animal cells were broken up in a salt solution which was then placed on top of the sucrose column.

The tube was then spun in a centrifuge.

This caused the cell components to move different distances down through the sucrose column according to their density.

The diagram shows the position of some cell components in the sucrose column after centrifugation.

The table shows the density of some cell organelles.

(a) Component W was present after centrifugation.

Explain what might be present in component W other than water and salt.(2)

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(b) Which row correctly identifies the organelles present in component X and component Y?

(1)

(c) Explain which other organelle would be present in component Z.

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(d) Explain how rough endoplasmic reticulum can be separated from smooth endoplasmic reticulum using density gradient centrifugation.

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Q4.

Microscopy is a technique used to study structures that are not within the resolution range of the human

eye.

* A school wanted to buy some new microscope objective lenses that would give better resolution.

Several factors affect the resolution of a microscope.

The tables show some data that the school was given from a company selling microscope objective lenses.

Table 1

Table 2

Analyse the data in Table 1 and Table 2 to determine the extent to which resolution is affected by magnification, numerical aperture and the wavelength of light.

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Q5.

Antibiotics can affect bacteria.

The table describes the mode of action of four antibiotics.

(i) Name the antibiotic that affects Gram positive bacteria only.

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(ii) Give one reason why these antibiotics will not affect human cells.

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Q6.

The photograph shows part of a bacterial cell surrounded by viruses, as seen using an electron microscope.

(i) Which of these structures would be present in a bacterial cell but absent in a palisade mesophyll cell?

(1) A cellulose cell wall and nucleoid B cellulose cell wall and nucleolus C peptidoglycan cell wall and nucleoid D peptidoglycan cell wall and nucleolus

(ii) Which virus contains DNA?

(1) A Ebola B HIV C λ (lambda) phage D tobacco mosaic

(iii) Explain why an electron microscope, rather than a light microscope, was used to produce this photograph.

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Q7.

The pancreas is an organ that secretes digestive enzymes.

The electron micrograph shows part of a secretory cell from a human pancreas.

Calculate the maximum diameter of organelle Q.

(2)

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Q8.

In flowering plants, pollen grains grow pollen tubes that are involved in fertilisation, producing a zygote and endosperm.

A scientist investigated the effects of chemical A and chemical B on pollen tube growth. Chemical A prevents transcription. Chemical B prevents translation. Pollen grains were treated with different concentrations of these two chemicals. The lengths of the pollen tubes they produced were compared with a control group of pollen grains. The lengths of the pollen tubes were measured and expressed as a percentage of the control group. The results are shown in the graphs.

(i) The mean length of the pollen tubes in the control group was 7.5 mm.

Calculate the mean length of the pollen tubes after adding 0.010 μg cm–3 of chemical A.(2)

Answer ...........................................................

(ii) Analyse the data to comment on the effects of chemical A and chemical B on the roles of transcription and translation in pollen tube growth.

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Q9.

In animals, sperm cells and egg cells are involved in sexual reproduction.

The photomicrographs show human sperm cells and a human egg cell. They are not shown to scale.

Using an eyepiece graticule (micrometer), the head of a human sperm cell was measured as 5 μm in length and the egg cell 0.1 mm in width.

Calculate how many times larger the egg cell is compared to the head of the sperm cell.

(2)

Answer ...........................................................

Q10.

The diagram shows a section of plant stem with a vascular bundle stained with phloroglucinol.

Phloroglucinol stains xylem vessels.

These xylem vessels can then be seen more easily and their size measured using a light microscope and an eyepiece graticule (micrometer).

(i) The xylem vessel labelled is 0.133 mm in diameter. Calculate the magnification used. Give your answer to two significant figures.

(1)

Answer ...........................................................

(ii) A student cut a section of plant stem from a shoot tip and stained it with phloroglucinol. She used an eyepiece graticule (micrometer) to measure the diameter of a xylem vessel.

She found that the xylem vessel was 0.39 mm in diameter.Explain how you would extend this procedure to obtain valid data showing that xylem vessels are larger in older parts of the plant.

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Q11.

Mitosis is one of the stages of the cell cycle.

The diagram represents some of the stages in the cell cycle.

The duration of each stage of the cell cycle is directly proportional to the number of cells in that stage.

A student made a squash preparation of a root tip and counted the number of cells in each stage of the cell cycle.

The results are shown in the table.

(i) The cells in this root tip had a cell cycle time of 23 hours.

Calculate the time, in minutes, that these cells spent in anaphase.(2)

Answer ........................................................... mins

(ii) The student then used the same method to study mitosis in a root tip from another plant of the same species.

The student worked out that the cells spent 8% less time in anaphase.Calculate the time, in minutes, that these cells spent in anaphase.

(2)

Answer ........................................................... mins

(iii) Explain why these two calculated values are not identical.

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Q12.

The diagram shows stages of the cell cycle.

A study of cell division in ovarian tumour cells compared the mean DNA concentration of cells in interphase with those in metaphase.

The results are shown in the table.

Explain the difference between the mean DNA concentration of cells in metaphase and cells in interphase.

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Q13.

In 2014, the British nurse Will Pooley contracted Ebola. He was given the experimental drug Zmapp and he recovered.

Zmapp contains three monoclonal antibodies that bind to Ebola glycoprotein.

Changes to viral proteins are essential for fusion of the virus with the host cell membrane.

This process delivers the viral RNA into the cell cytoplasm.

The model shows how the three monoclonal antibodies bind to the Ebola glycoprotein.

(i) Analyse the information to explain the success of Zmapp in treating patients with Ebola.

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(ii) The rate of mutation in the Ebola virus is as fast as that of the influenza virus.

The Ebola genome codes for seven proteins, one of which is the glycoprotein.

Explain what effect a mutation may have on the effectiveness of Zmapp.

(2)

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Q14.

Infertility reduces the chance of successful fertilisation of the egg by a sperm cell. There are many causes of infertility in humans.

One cause of infertility is cigarette smoking. Men who smoke cigarettes have a 30% higher risk of infertility.

Cigarette smoke contains nicotine. The effects of nicotine on the quality of sperm cells have been studied in rats.

Male rats were given nicotine at levels of either 0.5 mg per kg of body mass or 1.0 mg per kg of body mass.

The sperm cells produced by these rats were compared with sperm cells produced by a control group of rats. The rats in the control group were not exposed to nicotine. The defects in the sperm cells produced were recorded and the results are shown in the table below.

(i) Complete the table to give the percentage of sperm cells with flagella defects when the rats were given 0.5 mg of nicotine per kg of body mass.

(1)

(ii) Using the information in the table, calculate the difference in the percentage of sperm cells with defective flagella in rats given 1.0 mg of nicotine per kg of body mass compared with the control group.

(1)

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(iii) Name the organelle that may be missing from the sperm cells with mid-piece defects.

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(iv) Using the information in the table, suggest why nicotine reduces the movement of the sperm cells.

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Q15.


A study in 2015 showed that some tissues are far more likely to develop cancer than other tissues.

(i) Some tissue types divide more quickly than others.

This study suggested that there was a positive correlation of 0.81 between the chance of developing cancer and the rate of cell division in normal cells.Describe what is meant by this positive correlation of 0.81.

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(ii) The study also found that the cells of the intestinal lining divide very rapidly.

Explain how the stages in the cell cycle for these cells would be different to cells that divide more slowly.

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Q16.




Explain why the egg cell is much larger than the head of the sperm cell.

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Q17.


A study in 2015 showed that some tissues are far more likely to develop cancer than other tissues.

Give one similarity and one difference between organs and tissues.

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Q18.

Cancer cells undergo uncontrolled mitosis.

(i) Which of the following shows the correct number of cancerous cells there would be after a single cell carries out six mitotic cell divisions?

(1) A 26

B 62

C 23

D 32

(ii) Cytotoxic drugs prevent the proper formation of spindle fibres.Explain how these drugs will stop cancer cells dividing.

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Q19.

Insulin is a protein produced by beta cells in the pancreas. Insulin is synthesised on ribosomes, then modified and packaged in vesicles. It is stored in these vesicles until it is secreted.

The diagram below shows the organelles involved in this process of modifying and packaging the insulin in vesicles.

* Using the information in the diagram, describe how insulin is modified, packaged and secreted by the cell.

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Q20.

A sea urchin is an invertebrate animal that lives on the seabed.

The photograph shows a sea urchin.

Sea urchin embryos are often used to study embryonic development. In the early stages of embryonic development, a sea urchin embryo is similar to a mammalian embryo.

(a) A scientist observed a fertilised sea urchin egg during the first few days after fertilisation.

Explain how this fertilised egg became a hollow structure.(3)

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(b) The scientist found that 128 cells were present after a few days.

Calculate the number of rounds of cleavage that had taken place.(1)

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Q21.

Mosquitoes have cells with a diploid number (2n) of six.

The diagram shows two cells from a male mosquito at different stages of meiosis.

(i) Which row of the table shows the stages of meiosis of cells P and Q?

(1)

(ii) Non-disjunction occurred during meiosis I.

Which of the following shows the number of chromosomes in each of the four sperm cells produced?

(1) A 4, 3, 3, 2 B 4, 4, 2, 2 C 6, 6, 7, 5 D 7, 7, 5, 5


Q22.

In December 2013, a boy died of Ebola Virus Disease (EVD) in Guinea, West Africa.

However, it was not until March 2014 that health officials reported a mysterious haemorrhagic fever that 'strikes like lightning'.

By the end of 2014, an estimated 20 000 cases had been reported.

The graph shows the number of deaths reported in the months following the outbreak in December 2013.

(a) Control measures may include the use of antiviral drugs. Which of the following describes how antiviral drugs work?

(1)

A disruption of the cell membrane

B inhibition of aerobic respiration

C inhibition of replication

D interference with cell wall production

*(b) In many remote areas of West Africa, dead bodies are washed by hand before burial.

Discuss the ethical dilemmas and practical problems for the foreign health workers when trying to

control the spread of EVD.(6)

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Q23.

In December 2013, a boy died of Ebola Virus Disease (EVD) in Guinea, West Africa.

However, it was not until March 2014 that health officials reported a mysterious haemorrhagic fever that 'strikes like lightning'.

By the end of 2014, an estimated 20 000 cases had been reported.

The graph shows the number of deaths reported in the months following the outbreak in December 2013.

(i) Give an estimate of the percentage of reported cases who had died by the end of 2014.

(1)

Answer ........................................................... %

(ii) Analyse the data for July to August 2014, and December 2014 to January 2015, to explain whether

the measures taken to control the spread of Ebola have been effective.

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(iii) The table shows the number of reported cases and deaths from Ebola in three different countries by March 2015.

Explain the difference between the percentage of reported cases who had died in these three countries.

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Q24.

Down's syndrome in humans is caused by non-disjunction.

The chance of having a baby with Down's syndrome increases as the age of the mother increases.

At age 40, the probability of having a baby with Down's syndrome is 0.018.

In 2016 the number of women aged 40 in the UK was estimated to be 500 000.

The pregnancy rate for women in the UK aged 40 is 14 pregnancies per 1000 women per year.

Calculate the number of babies with Down's syndrome that were expected in 2016 in the UK.

(2)

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Q25.

Mitosis in plant tissue is a form of cell division that is affected by a number of factors.

(a) A student carried out an investigation into the effect of environmental stress on mitosis in one species of bean plant.

Sixty bean plants were divided into four groups of 15, labelled A, B, C and D. All the groups were grown in a complete mineral solution.After 15 days, the bean plants from groups B, C and D were removed from this mineral solution for different lengths of time to stress them.Cells from the root were then observed and the percentage of cells undergoing mitosis was found for each group.The results are shown in the table.

(i) Analyse the data to explain why removing the plants from the mineral solution affects mitosis in the root cells.

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(ii) The student concluded that the decrease in the percentage of cells in mitosis was due to a lack of mineral ions during the stress period.

Give two reasons why this conclusion may not be valid.(2)

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(iii) For each group, the percentage of cells in the prophase stage of mitosis was recorded.The mean percentage of cells in prophase was calculated for groups B, C and D.These results are given in the table.

Explain the effect of environmental stress on the root cells of these bean plants.(2)

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*(b) The student suggested the hypothesis that mitosis rate increases as light intensity increases in bean plants.

Explain how this investigation could be modified to test this hypothesis in a safe, valid and reliable way.

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Q26.

Materials are transported into and out of a cell through the surface membrane.

(a) (i) Proteins are transported out of a cell by

(1) A active transport and diffusion B active transport and exocytosis C active transport and endocytosis D diffusion and exocytosis

*(ii) Cigarette smoke contains molecules called free radicals that damage the structure of cell membranes.

Explain the effect that cigarette smoke could have on the movement of molecules into and out of a cell.

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(b) The content of blood needs to be monitored when being stored for later use. In an investigation, samples of blood were stored at 4 °C for 5 days.

The concentration of potassium ions in the plasma and in the erythrocytes was measured at the beginning and end of storage.The results are shown in the table.

Calculate the percentage change in the concentration of potassium ions in erythrocytes during this storage at 4 °C for 5 days.

(2)

Answer ...........................................................

In another investigation, two blood samples, A and B, were stored at 4 °C for 5 days.

Sample A was then stored at 37 °C for 24 hours.

Glucose was added to sample B, which was stored at 37 °C for 24 hours.

The potassium ion concentration in the erythrocytes was recorded.

The results are shown in the graph.

(c) Analyse the data to explain the results of this investigation.

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Q27.

A student read that some plants do not grow well in waterlogged soil.

The student formed the following hypothesis:

Adding water to soil inhibits mitosis in root cells.

To test this hypothesis, the student grew onion roots in the apparatus shown.

The tips of the onion roots were removed and observed for stages of mitosis.

The photomicrograph shows a preparation from one onion root tip.

Devise a method the student should use to investigate the effect of waterlogged soil on mitosis in root cells.

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Q28.

When a photosynthetic plant cell grows, the number of chloroplasts in the cell increases. This increase in the number of chloroplasts can result from the division of chloroplasts already present in the cell.

The electron micrograph shows a chloroplast dividing.

The envelope consists of two membranes. These membranes are separated by a gap of 10 × 10−3 to 20 × 10−3 μm.

The magnification of this electron micrograph is ×12 000.

(i) Calculate the maximum width of this gap in this electron micrograph.

(2)

Answer ...........................................................

(ii) Explain why the envelope in this electron micrograph cannot be seen as two separate membranes.

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Q29.

In 2014, the British nurse Will Pooley contracted Ebola. He was given the experimental drug Zmapp and he recovered.

Zmapp contains three monoclonal antibodies that bind to Ebola glycoprotein.

Changes to viral proteins are essential for fusion of the virus with the host cell membrane.

This process delivers the viral RNA into the cell cytoplasm.

The model shows how the three monoclonal antibodies bind to the Ebola glycoprotein.

Zmapp is an experimental drug. Although it has not undergone clinical trials, animal testing has shown it to be effective.

Explain why the use of Zmapp to treat Will Pooley had ethical implications.

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Q30.

Some viruses cause infections in humans.

Antiviral drugs affect the virus without affecting the cells of the host.

Ebola is a disease that has a high mortality rate.

In 2014, there was an outbreak of Ebola in West Africa resulting in the deaths of over 11 000 people.

The graph shows the number of reported cases in Sierra Leone from March 2014 to January 2016.

The maps show the number of reported cases in districts of Sierra Leone, Guinea and Liberia in four months recorded during the outbreak.

The capital cities of these three countries are also shown.

During this outbreak of Ebola, no vaccine had been developed.

The World Health Organisation recommended that untested antiviral drugs could be used to treat patients, due to the scale of the outbreak.

Evaluate the ethical implications of using an untested drug during this outbreak.

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Q31.

Prokaryotes and eukaryotes are major divisions of cellular organisms.

(a) Which of the following would only be found in prokaryote cells?

(1) A nucleoid B nucleolus C nucleosome D nucleus

(b) A person had food poisoning caused by a bacterium.

Explain how antibiotic treatment could help to identify if the type of bacterium that caused the food poisoning was Gram positive or Gram negative.

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Q32.

In an investigation to determine the quantity of DNA in the nucleus of different cells from the plant Tradescantia paludosa, squash preparations of each tissue were stained for DNA in an identical manner.

The quantity of DNA in the nucleus of several cells was found by measuring the amount of light absorbed when the microscope was focused on a small area of the nucleus.

The results of this investigation are shown in the table below.

Analyse the data to explain the difference in the mean nuclear absorption of the nucleus of the different cells.

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Q33.

Eukaryotic cells and prokaryotic cells have similarities and differences in their ultrastructure.

Compare and contrast the ultrastructures of eukaryotic cells and prokaryotic cells.

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Q34.

Cellulose can be used to produce biofuel. The xylem tissue in wood is a good source of cellulose. The cell walls of this tissue are heavily lignified.

(i) Explain what is meant by the term tissue.

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(ii) The cellulose in the xylem tissue of wood has to be broken down by enzymes before it can be used to produce biofuels.

The lignin has to be removed before the enzymes can be used to break down the cellulose.

The photographs below show fibres containing cellulose before and after the removal of lignin.

Using the information from the photographs, suggest how lignin adds strength to xylem tissue.

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Q35.

In some diploid organisms, haploid cells are produced by meiosis.

The diagram shows an animal cell at various stages during the first division of meiosis.

(i) Identify the correct sequence in the diagram that shows the first division of meiosis.

(1) A 1, 2, 3, 4, 5 B 2, 5, 4, 1, 3 C 3, 2, 4, 1, 5 D 5, 4, 1, 2, 3

(ii) Identify the parts labelled P and Q.

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Q36.



(a) Explain what happens to the DNA content and the number of chromosomes in the stage labelled K.

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(b) Name the stage of the cell cycle labelled L.

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Q37.

The photograph below shows cells dividing by mitosis.

(a) The actual length of cell J is 23.5 μm.

(i) Calculate the magnification of this photograph.(3)

Answer ...........................................................

(ii) Describe what has happened in cell J.(4)

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(b) (i) Which sequence of letters represent the cells in order of their appearance in the phases of mitosis?

(1) A E, F, G, H, I, J B G, F, H, I, J, E C H, I, J, G, F, E D J, I, H, G, F, E

(ii) Give a reason why there are differences in the appearance of cells E and G.(1)

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Q38.

The classification of viruses is based on their structure and the type of nucleic acid that they contain.

(a) Which of the following is a reason why the influenza virus is classified as a retrovirus?

(1) A it has a capsid B it has an envelope C it contains RNA D it contains DNA

(b) Which of the following methods would be best for preventing the transmission of influenza through a population?

(1) A take paracetamol B wear a face mask C use insect repellent D take antibiotics

(c) Explain how the influenza virus has a pathogenic effect.

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Q39.

A student was investigating the structure of plant cells using a light microscope.

(i) Explain why iodine is used as a stain when looking at photosynthesising plant cells using a microscope.

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(ii) Iodine is also used as part of the Gram staining technique when identifying bacteria.

Explain why Gram positive and Gram negative bacteria stain in different ways.(2)

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(iii) When preparing a microscope slide for viewing cells, it is important to avoid small air bubbles.

Describe how a student would avoid small air bubbles when preparing a slide of plant tissue.(3)

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(iv) State why it is important to avoid small air bubbles on a microscope slide.

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Q40.

The diagram shows a leaf of Bryophyllum.

Some of the cells at the edges of the leaf divide to form buds. These buds can develop into individual plantlets.

The diagrams show the life cycles of two organisms, A and B.

(i) Which row of the table correctly describes the zygote of organism A and the gametes of organism B?

(1)

(ii) Which row in the table shows where meiosis occurs in each life cycle?

(1)

(iii) Explain the significance of meiosis in living organisms.

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Q41.

A student investigated the effect of light intensity on the development of stomata in coffee plant leaves.

The following method was used:

· young coffee seedlings were separated into two groups· one group was grown in bright light and the other group was grown in dim light· leaves were selected from each group and their surfaces were painted with nail varnish· the nail varnish was allowed to dry and then peeled off the leaf surface· each nail varnish peel was observed using a light microscope.

The diagram shows an example of the field of view seen by the student when using the high power lens.

The diagram shows one of the stomata drawn by the student.

The actual length of this stoma is 20 μm.

Calculate the magnification of this drawing.

(2)

Answer ...........................................................


Q42.




(i) Explain how meiosis results in genetic variation.

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(ii) One primary oocyte undergoes two meiotic divisions.

State how many egg cells are produced.(1)

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Q43.

A student investigated the effect of light intensity on the development of stomata in coffee plant leaves.

The following method was used:

· young coffee seedlings were separated into two groups· one group was grown in bright light and the other group was grown in dim light· leaves were selected from each group and their surfaces were painted with nail varnish· the nail varnish was allowed to dry and then peeled off the leaf surface· each nail varnish peel was observed using a light microscope.

The diagram shows an example of the field of view seen by the student when using the high power lens.

Describe how a microscope should be used to observe the stomata using the high power lens.

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Q44.

A sea urchin is an invertebrate animal that lives on the seabed.

The photograph shows a sea urchin.

Sea urchin embryos are often used to study embryonic development. In the early stages of embryonic development, a sea urchin embryo is similar to a mammalian embryo.

A scientist carefully removed one of the 128 cells from the hollow structure and injected fluorescent dye into its cytoplasm

She replaced this cell in a new position on the opposite side of the hollow structure.

The embryo then developed normally. The repositioned cell formed healthy tissue, appropriate to its new position.

The tissue formed by an embryonic cell is called the 'fate' of the cell.

(i) Explain how the scientist could identify the fate of the repositioned cell.

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(ii) The scientist found that repositioning this cell changed its fate.

Explain the scientist's finding.(4)

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Q45.

Microscopy is a technique used to study structures that are not within the resolution range of the human eye.

The photograph shows cells in a blood smear, as seen using a light microscope.

(i) Draw the cell labelled K, as shown in the photograph. Your drawing should have a magnification ×2.

(4)

(ii) Describe how to use a micrometer to determine how many times bigger your drawing is than the actual cell in the blood smear.

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Q46.

Leigh syndrome is a genetic disorder inherited from the mother. The mother carries genes for the disorder in her mitochondrial DNA.

Draw and label a mitochondrion.

(4)


Q47.

Food poisoning can be caused by food that is contaminated with pathogenic microorganisms.

A number of different viruses can cause food poisoning.

One virus that can cause food poisoning is the Norovirus.

Noroviruses are RNA viruses.

(i) The following four statements are features of viruses:

1. have envelopes

2. contain reverse transcriptase

3. surrounded by a protein coat

4. have a helical structure

Which of the following is correct for all RNA viruses?

(1)

A statement 1, statement 2 and statement 3

B statement 2 only

C statement 3 only

D statement 1 and statement 4

(ii) Which of the following groups of viruses are also RNA viruses?

(1)

A Ebola virus, human immunodeficiency virus and tobacco mosaic virus

B Ebola virus, λ phage and tobacco mosaic virus

C Human immunodeficiency virus, λ phage and tobacco mosaic virus

D λ phage and tobacco mosaic virus


Q48.

The diagram shows a leaf of Bryophyllum.

Some of the cells at the edges of the leaf divide to form buds. These buds can develop into individual plantlets.

(i) Name the type of nuclear division that produces the plantlets.

(1) .............................................................................................................................................

(ii) State two advantages of this type of reproduction.

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Q49.

In flowering plants, pollen grains grow pollen tubes that are involved in fertilisation, producing a zygote and endosperm.

(i) Which row of the table shows the correct description for these nuclei?

(1)

(ii) The production of plant cell gametes involves both mitosis and meiosis.

The graph shows the DNA content of a cell during the production of a pollen grain.(1)

The order of nuclear divisions shown in the graph is

A meiosis, mitosis, mitosis

B meiosis, mitosis, meiosis

C mitosis, meiosis, meiosis

D mitosis, mitosis, meiosis


Q50.

A student made a squash preparation of a root tip to observe the stages of mitosis.

The diagram shows the method that the student used.

The student was disappointed with the slide that had been prepared because the nuclei were poorly stained and no stages of mitosis could be seen.

(i) Explain why the student had to make sure that an appropriate stain was used.

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(ii) Describe the changes that need to be made to this method to allow stages of mitosis to be seen.

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Q51.

Some of the cells in the pancreas secrete proteins.

The diagram represents a pancreatic cell.

(i) The structure labelled Y represents the

(1) A centrioles B Golgi apparatus

C rough endoplasmic reticulum D smooth endoplasmic reticulum

(ii) The structure also found in a prokaryotic cell is labelled

(1) A W B X C Y D Z

(iii) Calculate the magnification of this cell.

(2)

Answer ...........................................................

(iv) Explain why these pancreatic cells contain large numbers of organelle Z.

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Q52.







Calculate the percentage of cells in this photomicrograph in anaphase.

(2)

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Q53.







Describe how to prepare a microscope slide of root tissue to show stages of mitosis.

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Q54.

Genetic variation results from the recombination of alleles during meiosis.

(i) Which row of the table correctly shows when independent assortment and crossing over take place during meiosis?

(1)

(ii) Describe the process of crossing over that occurs during meiosis.

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Q55.

Leigh syndrome is a genetic disorder inherited from the mother. The mother carries genes for the disorder in her mitochondrial DNA.

Scientists have developed a technique for producing 'three-parent' babies.

This ensures that a mother with Leigh syndrome will not pass on the genes for this disorder to her baby.

The technique involves:

· removing the nucleus from the ovum of the mother· removing the nucleus from the ovum of a donor female to produce an enucleated ovum· inserting the nucleus from the ovum of the mother into the enucleated donor ovum· fertilising this ovum with the sperm of the father to produce a zygote· implanting the resulting embryo into the uterus of the mother.

(i) The 'three-parent' baby produced by this technique will inherit mitochondrial DNA from the

(1) A donor female B donor female and father C mother D mother and father

(ii) Explain the importance of DNA replication during the development of this zygote into a blastocyst.

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Q56.

In some diploid organisms, haploid cells are produced by meiosis.

The diagram shows an animal cell at various stages during the first division of meiosis.

In mammals, meiosis occurs during oogenesis and spermatogenesis.

Describe how the products of oogenesis differ from the products of spermatogenesis in mammals.

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Q57.

In February 2016, the World Health Organisation (WHO) declared a public health emergency because of the spread of the Zika virus.

The mild symptoms, such as joint pains, headaches and a slight temperature increase lasted only a few days. However, Zika virus has been linked to a birth defect called microcephaly.

The graph shows the number of babies born with microcephaly in Brazil from 2010 to 2015.

Scientists have discovered that the Zika virus genome is made of RNA.

This RNA codes for:

· capsid protein with 105 amino acids· pre-membrane protein with 187 amino acids· envelope protein with 505 amino acids· seven nonstructural proteins

(i) State how many bases are needed to code for the capsid protein.

(1) .............................................................................................................................................

(ii) Unlike human immunodeficiency virus (HIV), Zika is not a retrovirus.

Describe what happens to the Zika RNA once it is in the cell.(2)

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Q58.

The retina contains rod cells and bipolar neurones.

Rod cells contain large numbers of mitochondria.

Explain the role of mitochondria in the functioning of rod cells.

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Q59.



Explain why cells carry out mitosis.

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Q60.



Ebola is a disease that has a high mortality rate.

In 2014, there was an outbreak of Ebola in West Africa resulting in the deaths of over 11 000 people.

The graph shows the number of reported cases in Sierra Leone from March 2014 to January 2016.

The maps show the number of reported cases in districts of Sierra Leone, Guinea and Liberia in four months recorded during the outbreak.

The capital cities of these three countries are also shown.

* (i) Analyse the information in the graph and maps to comment on the spread of Ebola in West Africa.

(6)(ii) Describe the methods used to prevent the spread of Ebola.

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Q61.

Leukaemia is a type of cancer involving abnormal white blood cells.

In 2015, scientists announced that 1 in 5 people aged 90 or over had mutations linked to leukaemia.

The current UK population is about 64 million, of which 0.8% are aged 90 or over.

Leukaemia cells have a rapid growth rate and they tend to be small.

The cell cycle consists of three stages, interphase, mitosis and cytokinesis.

Explain which of these three stages would be shorter in a leukaemia cell.

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Q62.

Infertility reduces the chance of successful fertilisation of the egg by a sperm cell. There are many causes of infertility in humans.

One cause of infertility is cigarette smoking. Men who smoke cigarettes have a 30% higher risk of infertility.

Cigarette smoke contains nicotine. The effects of nicotine on the quality of sperm cells have been studied in rats.

Male rats were given nicotine at levels of either 0.5 mg per kg of body mass or 1.0 mg per kg of body mass.

The sperm cells produced by these rats were compared with sperm cells produced by a control group of rats. The rats in the control group were not exposed to nicotine. The defects in the sperm cells produced were recorded and the results are shown in the table below.

A genetic cause of infertility is globozoospermia.

This condition results in round-headed sperm cells being produced. These sperm cells do not possess an acrosome.

Photograph A shows normal sperm cells and photograph B shows sperm cells from a man with globozoospermia.

Suggest why the sperm cells in photograph B would not be able to fertilise an egg.

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Q63.

Viruses possess some of the features of living organisms.

(i) Which of the following are found in all viruses?

(1)

A DNA and protein

B RNA and protein

C nucleic acid and protein

D nucleic acid and ribosomes

(ii) Which of the following is a retrovirus?

(1)

A Ebolavirus

B human immunodeficiency virus

C λ (lambda) phage

D tobacco mosaic virus

Q64.

Place a cross in the box next to the correct word or words to complete each of the following statements.

(i) Plant and animal cells may both contain

(1)

A amyloplasts, centrioles and mitochondria

B centrioles, mitochondria and rough endoplasmic reticulum

C chloroplasts, mitochondria and rough endoplasmic reticulum

D mitochondria, rough endoplasmic reticulum and smooth endoplasmic reticulum

(ii) The cytoplasmic connections between one plant cell and another are known as

(1)

A middle lamellae

B plasmodesmata

C pits

D tonoplasts

(iii) Prokaryotic cells and plant cells both contain

(1)

A a cell membrane and chloroplasts

B a cell membrane and mesosomes

C a cell wall and chloroplasts

D a cell wall and ribosomes

(iv) Woese suggested that there are three domains based on evidence from

(1)

A molecular pharmacology

B molecular phylogeny

C molecular physiology

D phenetic taxonomy

(v) The two domains that contain prokaryotic cells are

(1)

A Animalia and Bacteria

B Archaea and Bacteria

C Bacteria and Eukarya

D Bacteria and Plantae

Q65.

When a bacterial cell is infected with λ (lambda) phage, the virus will enter the lytic cycle.

(i) Describe the lytic cycle of a virus.

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(ii) The multiplicity of infection (MOI) is one factor that determines whether a virus enters the lytic cycle or latency.

A scientist needed to use a MOI of 0.5 for an investigation.The virus particles were at a concentration of 2 × 109 cm–3 and the bacteria were at a concentration of 8 × 108 cm–3.Calculate the volume of virus particles that should be added to 0.25 cm3 of bacteria.

(3)

Answer ........................................................... cm3


Q66.

The pancreas is an organ that secretes digestive enzymes.

The electron micrograph shows part of a secretory cell from a human pancreas.

Describe the role of the Golgi body in producing secreted enzymes.

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Q67.

In February 2016, the World Health Organisation (WHO) declared a public health emergency because of

the spread of the Zika virus.



Zika virus is transmitted to humans by infected mosquitoes.

(i) Explain why another type of drug, rather than antibiotics, has to be used to treat Zika virus infections.

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(ii) Scientists have suggested that genetically modified (GM) mosquitoes could be used to help combat the spread of the Zika virus.

Mosquito eggs are injected with DNA, from GM mosquitoes. This DNA contains a gene for fluorescence. However, only one in a few thousand injected eggs results in a GM mosquito.Explain how this procedure could help in the production of large numbers of GM mosquitoes.

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(iii) Explain why the Brazilian government has advised people to use mosquito nets, even if they have already contracted the Zika virus.

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Q68.

Describe two ways in which viruses replicate.

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Q69.

The details of the ultrastructure of a cell can be seen using an electron microscope.

Complete the table below. If the organelle can be present, place a tick ( ) in the box and if the organelle could not be present, place a cross ( ) in the box.

(4)

Q70.

A student decided to investigate how many cells were undergoing cell division in different areas of a root. She grew some onion roots in a conical flask containing water, as shown in the diagram below.

She examined a root tip squash and counted the number of cells undergoing mitosis and the total number of cells in the field of view and calculated the mitotic index using the following formula.

The student determined the mitotic index of cells at five distances from an onion root tip. She repeated this procedure six times.Her results are shown in the table below.

The student concluded that there is a negative correlation between the mitotic index and the distance from the root tip in plants.However, this conclusion may not be valid because the investigation has limitations.(i) Give one way in which the student could modify her procedure to reduce the effect of a named limitation.

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(ii) Weeds reduce the yield of commercial crops that grow in fields. Some herbicides that are sprayed onto soil kill weeds by preventing mitosis.

Explain how the student could modify her investigation to find the herbicide concentration that is most effective at preventing mitosis.

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Q71.

Sickle cell anaemia is caused by a mutation in the β-globin gene which codes for part of haemoglobin.

The diagram shows the first 10 amino acids in this part of haemoglobin, in a healthy person and in a person with sickle cell anaemia.

People who are homozygous for the HbS allele develop sickle cell anaemia.

People who are heterozygous for HbS produce both forms of haemoglobin. These individuals have some sickled red blood cells.

People with the HbS allele are less likely to get malaria.

You are provided with a blood sample from a patient with malaria and a blood sample from a healthy individual.

Devise a method that would allow you to distinguish between the two blood samples.

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Q72.

Cattle with bovine spongiform encephalopathy (BSE) have microscopic holes in their brain tissue.

This disease involves the misfolding of proteins which then form clumps.

Clumps of misfolded proteins can be seen with an electron microscope.

BSE is diagnosed by examination of brain tissue.

(i) Explain why the clumps of misfolded proteins can be seen with an electron microscope, but not with a light microscope.

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(ii) Explain why stains are used when preparing tissue for examination using a light microscope.

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Q73.

The classification of viruses is based on structure and nucleic acid types.

(i) Which of the following pairs of viruses both have an envelope?

(1)

A Ebola and λ (lambda) phage

B human immunodeficiency virus and Ebola

C λ (lambda) phage and tobacco mosaic virus

D tobacco mosaic virus and human immunodeficiency virus

(ii) Which of the following pairs of viruses both have a helical capsid?

(1)

A Ebola and tobacco mosaic virus

B λ (lambda) phage and Ebola

C human immunodeficiency virus and λ (lambda) phage

D tobacco mosaic virus and human immunodeficiency virus


Q74.



Explain why viruses are dependent on living cells.

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Q75.

In February 2016, the World Health Organisation (WHO) declared a public health emergency because of the spread of the Zika virus.



Calculate the percentage increase in the number of babies born with microcephaly in 2015 compared with 2014.

(2)

Answer ........................................................... %


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