AQA A-Level Biology 2027 Predicted Practice Paper — Paper 1

Answer ALL questions. Write your answers in the spaces provided. You must write down all the stages in your working.

Section A

Short-answer and structured questions. Answer ALL questions.

• 1

  Question SECTION-A1 (6 marks)

  The enzyme sucrase catalyses the hydrolysis of sucrose into glucose and fructose. A student investigated the effect of temperature on the initial rate of reaction using a fixed concentration of sucrose and a fixed concentration of sucrase. (a) Describe how you would measure the initial rate of this reaction, and explain why the INITIAL rate, rather than a later rate, is used. (3 marks) (b) The student found that the rate increased from 10 degrees C to an optimum at 40 degrees C, then fell sharply to zero at 60 degrees C. Explain, in terms of molecular behaviour and enzyme structure, the shape of this curve. (3 marks)

  (Total for Question SECTION-A1 is 6 marks)
• 2

  Question SECTION-A2 (7 marks)

  Figure 1 (described) shows a plant cell placed in a solution. A plant cell has a water potential of -800 kPa. It is placed in a sucrose solution with a water potential of -450 kPa. (a) Define the term water potential and state its value for pure water at atmospheric pressure. (2 marks) (b) State and explain the direction of net water movement between the cell and the solution in the description above. (2 marks) (c) The cell is then transferred to distilled water. Explain how the pressure potential of the cell changes and how this prevents the cell from bursting. (3 marks)

  (Total for Question SECTION-A2 is 7 marks)
• 3

  Question SECTION-A3 (7 marks)

  Antibodies are proteins produced during the specific immune response. (a) Describe the structure of an antibody molecule. (3 marks) (b) Explain how the arrival of a pathogen leads to the production of large numbers of antibodies specific to that pathogen, referring to the roles of B cells and T helper cells. (4 marks)

  (Total for Question SECTION-A3 is 7 marks)
• 4

  Question SECTION-A4 (8 marks)

  Figure 2 (described) shows the pressure changes in the left atrium, left ventricle and aorta during one cardiac cycle. (a) Using your knowledge of pressure changes, explain what causes the atrioventricular (bicuspid) valve to close and what causes the semilunar (aortic) valve to open. (3 marks) (b) A person has a heart rate of 75 beats per minute. Calculate the duration of one cardiac cycle in seconds. (1 mark) (c) During ventricular diastole the ventricle fills with blood. Explain how the structure of the ventricle wall and the pressure changes allow efficient filling. (4 marks)

  (Total for Question SECTION-A4 is 8 marks)
• 5

  Question SECTION-A5 (7 marks)

  DNA replication is described as semi-conservative. (a) Explain what is meant by semi-conservative replication. (2 marks) (b) Describe the roles of helicase and DNA polymerase in DNA replication. (3 marks) (c) A section of DNA contains 1200 nucleotides, of which 360 contain the base guanine. Calculate the number of nucleotides in this section that contain the base adenine. Show your working. (2 marks)

  (Total for Question SECTION-A5 is 7 marks)
• 6

  Question SECTION-A6 (6 marks)

  Gas exchange in an insect occurs through a system of tracheae and tracheoles. (a) Describe how oxygen reaches the respiring tissues of an insect. (3 marks) (b) Insects are adapted to reduce water loss. Explain how two features of the insect gas exchange system reduce water loss while still allowing gas exchange. (3 marks)

  (Total for Question SECTION-A6 is 6 marks)
• 7

  Question SECTION-A7 (8 marks)

  The light-dependent reactions of photosynthesis take place in the thylakoid membranes of chloroplasts. (a) Describe the role of light energy and water in the light-dependent reactions, including the products formed. (4 marks) (b) Explain how the products of the light-dependent reactions are used in the light-independent reaction (Calvin cycle). (4 marks)

  (Total for Question SECTION-A7 is 8 marks)
• 8

  Question SECTION-A8 (8 marks)

  A student investigated the effect of exercise on breathing rate. At rest, a person's breathing rate was 12 breaths per minute with a tidal volume of 0.5 dm^3. After exercise, breathing rate rose to 30 breaths per minute with a tidal volume of 2.4 dm^3. (a) Calculate the percentage increase in pulmonary ventilation rate (minute ventilation) after exercise compared with rest. Show your working. (3 marks) (b) Explain how a rise in carbon dioxide concentration in the blood leads to an increased breathing rate. (5 marks)

  (Total for Question SECTION-A8 is 8 marks)
• 9

  Question SECTION-A9 (8 marks)

  Natural selection can lead to antibiotic resistance in a population of bacteria. (a) Explain how the repeated use of an antibiotic can lead to a population of bacteria that is resistant to that antibiotic. (4 marks) (b) Describe how the directional selection seen in (a) differs from stabilising selection, giving one example of stabilising selection. (4 marks)

  (Total for Question SECTION-A9 is 8 marks)

Section B

Extended response and synoptic questions. Answer ALL questions.

• 1

  Question SECTION-B1 (9 marks)

  Cell membranes control the movement of substances into and out of cells. Describe the fluid-mosaic model of the cell-surface membrane and explain how substances are transported across it by facilitated diffusion, active transport and co-transport. Use named examples where appropriate. (9 marks)

  (Total for Question SECTION-B1 is 9 marks)
• 2

  Question SECTION-B2 (9 marks)

  The kidney produces urine and plays a central role in osmoregulation. Describe how ultrafiltration and selective reabsorption produce glomerular filtrate and then modify it, and explain how the concentration of urine is controlled when the water potential of the blood falls. (9 marks)

  (Total for Question SECTION-B2 is 9 marks)
• 3

  Question SECTION-B3 (8 marks)

  Respiration releases energy from organic molecules in the form of ATP. Compare aerobic respiration and anaerobic respiration in eukaryotic cells, explaining where each stage occurs, the relative ATP yields, and why the yields differ. Include reference to the role of oxygen. (8 marks)

  (Total for Question SECTION-B3 is 8 marks)