Aqa A-level biology paper 1, Essays (high school) of Biology

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AQA A-level Biology

Mock Practice Paper 1

(this mock paper is not produced by AQA, it is a mixture of past paper question published on their website to create a mock paper)

91 marks

Time allowed: 2 hours

Materials

For this paper you must have:

• a ruler with millimetre measurements
• a scientific calculator.

Instructions

• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page.
• Answer all questions in Section A.
• Answer one question from Section B.
• You must answer the questions in the spaces provided. Do not write

outside the box around each page or on blank pages.

• If you need extra space for your answer(s), use the lined pages at the end of

this book. Write the question number against your answer(s).

• Show all your working.
• Do all rough work in this book. Cross through any work you do not want

to be marked.

Information

- The marks for the questions are shown in brackets.

• The maximum mark for this paper is 91.

For more resources to help you to improve and to reach an A/A* , try the

following resources:

1. To help you to create flashcards and review the content:

Summary Topic videos playlist on YouTube: All the theory

summarised for each entire topic

2. To improve your memory of the theory and learn key marking points:

Use my active recall workbook. Students love it!

3. To learn the theory, key marking points and essay links: Try my A-

level notes

Q1.

The diagram below shows part of a DNA molecule. (a) Name the type of bond between: complementary base pairs _______________________________________ adjacent nucleotides in a DNA strand _______________________________ (2) (b) The length of a gene is described as the number of nucleotide base pairs it contains. Use information in above diagram to calculate the length of a gene containing 4.38 × 103 base pairs. Answer _______________ nm (2) (c) Describe two differences between the structure of a tRNA molecule and the structure of an mRNA molecule. 1 _________________________________________________________________

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(2)

(d) In a eukaryotic cell, the structure of the mRNA used in translation is different from the structure of the pre-mRNA produced by transcription. Describe and explain a difference in the structure of these mRNA molecules.

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(2) (Total 8 marks)

Q2.

Uronema marinum is a single-celled eukaryotic organism. The diagram below is a photograph of U. marinum taken through an optical microscope. (a) Explain why it is not possible to determine the identity of the structures labelled X using an optical microscope.

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(2)

(b) U. marinum cells ingest bacteria and digest them in the cytoplasm. Describe the role of one named organelle in digesting these bacteria.

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(3) (c) Calculate the actual length of the cell shown between Y and Z in the diagram above. The magnification of the image is × 900 Give your answer in μm and to 2 significant figures. Show your working. Answer __________ μm (2) (d) In large cells of U. marinum , most mitochondria are found close to the cell-surface membrane. In smaller cells, the mitochondria are distributed evenly throughout the cytoplasm. Mitochondria use oxygen during aerobic respiration. Use this information and your knowledge of surface area to volume ratios to suggest an explanation for the position of mitochondria in large U. marinum cells.

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(2) (Total 9 marks)

Q3.

(a) Cells lining the ileum of mammals absorb the monosaccharide glucose by co- transport with sodium ions. Explain how.

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(3) A student set up the experiment shown in the diagram below. The material from which Visking tubing is made is partially permeable. After 15 minutes, the student removed samples from the liquid in the beaker and from the liquid inside the Visking tubing. She carried out biochemical tests on these samples. She drew the table below to record her results.

(b) Complete the table by placing a tick (✔) in each box that you expect to have shown a positive result. Biochemical test Liquid from beaker Liquid inside Visking tubing Biuret reagent Iodine in potassium iodide Benedict’s solution (3) (c) Justify your answers to part (b).

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(3) (Total 9 marks)

Q4.

A student investigated the activity of the enzyme amylase. He cut three identical wells ( D , E and F ) in starch-agar in a Petri dish. He added 0.2 cm^3 of:

• amylase solution to well D
• boiled amylase solution to well E
• water to well F. After 60 minutes, he covered the starch-agar with iodine solution. The figure below shows his results. (a) Explain the appearance of the agar in the clear area surrounding well D.

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(b) What can you conclude about the activity of amylase from the appearance of the agar surrounding well E and well F in the figure above? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (2)

(c) The student cut out a piece of agar from the clear area surrounding well D. He obtained a solution of the substances contained in this piece of agar. Describe a different biochemical test the student could use with this solution to confirm that amylase had affected the starch in the clear area surrounding well D.

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(2) The diameter of the clear area around well D is 18 mm In a different investigation, the student prepared a dilution of the amylase solution. He did this by mixing amylase solution and water in the volumes shown in the table below. Amylase solution / cm^3 Water / cm^3 1.6 2. He prepared a starch-agar Petri dish identical to the figure above, but with a single well. He added 0.2 cm^3 of the diluted amylase solution to this well and left the Petri dish for 60 minutes. (d) Use all of this information to predict the diameter of the clear area that will form around the well containing the diluted amylase solution. Give your answer to the nearest whole number. Show your working. Answer __________ mm (2) (e) The student used a ruler to measure the diameter in mm of the clear area around

well D in the figure above. Use this information to explain why the answer to part (d) should be given to the nearest whole number.

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(1) (Total 9 marks)

Q5.

(a) Littorina littorea is a species of snail found on rocky sea shores. A student investigated variation in snail shell height in two populations of snails. Give two ways in which the student could ensure his samples would provide a reliable measure of the variation between individuals in each population. 1 _________________________________________________________________

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(2) (b) The student could determine the median, mode and range from his measurement of shell heights in these populations. Give two other statistical values the student could calculate from his measurement of shell heights in these populations. 1 ___________________________________ 2 ___________________________________ (1) (c) Name the taxon in the hierarchy of classification represented by: 1 Littorina __________________________ 2 Iittorea ___________________________ (1)

(d) The student noticed there was a difference in shell height between these populations of snails. He wanted to investigate if the difference was significant. Give a suitable null hypothesis to use in his investigation and name the statistical test to use with these data. Null hypothesis _____________________________________________________

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Statistical test ______________________________________________________

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(2) (Total 6 marks)

Q6.

(a) Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake.

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(2) Figure 1 shows two models of oxygen uptake found in animals. Figure 1

(b) Suggest how the environmental conditions have resulted in adaptations of systems using Model A rather than Model B.

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(2) (c) Figure 2 shows changes in concentration of oxygen in two gas exchange systems. Figure 2 A student studied Figure 2 and concluded that the fish gas exchange system is more efficient than the human gas exchange system.

Use Figure 2 to justify this conclusion.

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(2) (d) Explain how the counter-current principle allows efficient oxygen uptake in the fish gas exchange system.

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(2) (e) The table below shows features of two mammals. Bats are flying mammals; shrews are ground-living mammals. Mammal Mean body mass / kg Mean lung volume / cm^3 Bat 0.096 12. Shrew 0.024 0. Calculate how many times the lung volume per unit of body mass of the bat is greater than that of the shrew. Give your answer to an appropriate number of significant figures. Give one suggestion to explain this difference.

Answer _______________ Explanation ________________________________________________________

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(3) (Total 11 marks)

Q7.

Uncontrolled cell division can cause tumours to form. Figure 1 shows the growth pattern followed by a type of tumour. Figure 1 (a) Use Figure 1 to calculate the percentage of maximum growth this type of tumour

reaches before it can be detected. You will need to use the 10x^ button on your calculator. Answer = _________________________% (1) (b) Figure 1 can also be used to calculate the age of this type of tumour. At diagnosis, a patient had a tumour of 3.98 × 10^11 cells. Calculate the age of the tumour. You will need to use the log 10 button on your calculator. Answer = _________________________ years (1) Trexall is a drug that can be used to slow the development of various forms of cancer. Trexall slows cell division by interacting with an enzyme called dihydrofolate reductase (DR). DR is involved in making nucleotides; the substrate for DR is folic acid. Figure 2 shows the chemical structure of Trexall. Figure 3 shows the chemical structure of folic acid. Figure 2 Figure 3

(c) Use the information provided to suggest how Trexall slows cell division.

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(3) Doctors investigated how the concentration of Trexall given to patients affected the growth of lung tumours. The doctors measured the volume of tumours at the beginning of the study and after 8 months. Figure 4 shows the results of this investigation. The bars represent ± 2 standard deviations. A value of ± 2 standard deviations from the mean includes over 95% of the data. Figure 4

(d) The scientists measured the percentage change in tumour volume. Suggest why they recorded both percentage change and tumour volume. Percentage change ___________________________________________________

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Tumour volume ______________________________________________________

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(2) (e) A lung cancer patient received 15 mg of Trexall per week. After treatment, the diameter of his lung tumour was 35.8 mm Assuming the tumour was spherical, use the mean percentage change in tumour volume shown in Figure 4 to calculate the volume of the patient’s tumour before treatment with Trexall.

The formula for the volume of a sphere is where π = 3.

Answer = _________________________ mm^3 (2) (f) To reduce the size of tumours, would it be better to use 30 mg of Trexall per week, or 20 mg of Trexall per week? Explain your answer.

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(2) Trexall can also be used to slow the development of rheumatoid arthritis (a pain-causing joint disease). Scientists investigated the effectiveness of Trexall as a pain relief treatment in 12 rheumatoid arthritis patients. All of the patients were female. They randomly divided the patients into two groups:

• Group R received Trexall tablets for 35 days
• Group S was a control group. They asked both groups to rate their pain on a scale of 0–10 (0 being no pain and 10 being the worst pain possible) at the start and then every 7 days for 35 days. They calculated mean scores for each group. Their results can be seen in the table.

Number of days of treatment Mean score for severity of pain (scale 0–10) Group R Group S 0 9.7 9. 7 8.2 9. 14 8.4 8. 21 7.6 7. 28 6.3 7. 35 5.1 7. (g) Apart from age and general health, give two important factors when choosing patients for this investigation. 1 _________________________________________________________________ 2 _________________________________________________________________ (1) (h) A student analysed the table above and concluded that Trexall was effective in reducing pain in arthritis patients. Evaluate the student’s conclusion.

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(3) (Total 15 marks)

Q8.

(a) A scientist measured the pressure in a phloem tube in a willow plant stem. He repeated his measurements to obtain nine readings. His results are shown in the table below. Phloem pressure / arbitrary units

7.4 8.0 7.0 8.6 8.2 9.3 7.4 9.1 8.

The percentage error of the mean phloem pressure in this phloem tube is calculated using this equation. The uncertainty in measurement is half the range of the measured values.Calculate the percentage error of the mean phloem pressure in this phloem tube. Show your working. Percentage error _______________ % (2) (b) The mass flow hypothesis is used to explain the movement of substances through phloem. Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube.

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(3) (c) The scientist also measured changes in the phloem pressure and changes in the rate of water movement in the xylem of a willow plant at intervals during a day. His results are shown in the graph below.

Describe the relationship between phloem pressure and the rate of water movement in xylem in this plant.

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(1) (d) Phloem pressure is reduced during the hottest part of the day. Use information in the graph above along with your understanding of transpiration and mass flow to explain why.

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(3) (Total 9 marks)

Q9.

Bacterial meningitis is a potentially fatal disease affecting the membranes around the brain. Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis. (a) In the UK, children are vaccinated against this disease. Describe how vaccination can lead to protection against bacterial meningitis.

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(6)

(b) Penicillin has been the antibiotic of choice for the treatment of bacterial meningitis. Since the year 2000, strains of Neisseria meningitidis that are resistant to penicillin, sulfonamides and rifampin have been discovered in the UK. Describe how a population of Neisseria meningitidis (Nm) can become resistant to these antibiotics.

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(4) (c) Contrast the structure of a bacterial cell and the structure of a human cell.

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(5) (Total 15 marks)

Mark schemes

Q1.

(a) 1. Hydrogen (bonds);

2. Phosphodiester (bonds); Accept ester/covalent bond 2 (b) Correct answer for 2 marks = 1489/1489.2;; Incorrect answer but for 1 mark accept: 876 OR 1861 - 1862 2 (c) 1. tRNA is 'clover leaf shape', mRNA is linear; Must be a comparison Reject tRNA is double stranded Accept tRNA is folded for tRNA is ‘clover leaf shaped’
3. tRNA has hydrogen bonds, mRNA does not;
4. tRNA has an amino acid binding site, mRNA does not; Accept ‘CCA end' for amino acid binding site
5. tRNA has anticodon, mRNA has codon; 2 (d) 1. mRNA fewer nucleotides OR Pre-mRNA more nucleotides OR mRNA has no introns/has (only) exons OR Pre-mRNA has (exons and) introns; Accept mRNA is shorter OR pre-mRNA is longer
6. (Because of) splicing; 2 [8]

Q2.

(a) 1. Resolution (too) low;

2. Because wavelength of light is (too) long; 2 (b) 1. Lysosomes;
3. Fuse with vesicle; Accept phagosome for vesicle
4. (Releases) hydrolytic enzymes; Accept lysozymes for "hydrolytic enzymes" Accept ‘Ribosomes/ Rough endoplasmic reticulum form hydrolytic enzymes = 2 marks Accept ‘Golgi body forms lysosomes’ = 2 marks Accept ‘Golgi body / ribosomes / rough endoplasmic reticulum’ for 1 mark if no other mark awarded. 3 (c) Correct answer for 2 marks = 32;; Accept for 1 mark, 29 000 (correct conversion to μm) OR 32.2 (correct answer but incorrect significant figures) OR OR An incorrect answer that shows division by 900 2 (d) 1. Large(r) cells have small(er) surface area to volume ratio;
5. (Takes) longer for oxygen to diffuse (to mitochondria) OR Less/no oxygen diffuses (to mitochondria) OR Diffusion distance/pathway is long(er); Accept converse for all marking points. 2 [9]

Q3.

(a) 1. Sodium ions actively transported from ileum cell to blood;