OCR A-Level Biology 2027 Predicted Practice Paper — Biological Processes

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

Section A

Multiple choice. Answer ALL the questions.

• 1

  Question SECTION-A1 (1 mark)

  Which structure is present in a prokaryotic cell but ABSENT from a typical eukaryotic animal cell?

  A. RibosomesB. A cell surface membraneC. Circular DNA free in the cytoplasmD. Cytoplasm

  (Total for Question SECTION-A1 is 1 mark)
• 2

  Question SECTION-A2 (1 mark)

  An enzyme-catalysed reaction is run at 25 degrees C. When a competitive inhibitor is added at fixed enzyme concentration, which change occurs as substrate concentration is greatly increased?

  A. The maximum rate (Vmax) is unchanged but is reached at a higher substrate concentrationB. The maximum rate (Vmax) is permanently reducedC. The enzyme is denaturedD. No product can ever be formed

  (Total for Question SECTION-A2 is 1 mark)
• 3

  Question SECTION-A3 (1 mark)

  Which row correctly pairs a biological molecule with the bond formed during its condensation synthesis?

  A. Triglyceride - glycosidic bondB. Polypeptide - peptide bondC. Polysaccharide - ester bondD. Dipeptide - hydrogen bond

  (Total for Question SECTION-A3 is 1 mark)
• 4

  Question SECTION-A4 (1 mark)

  During the light-dependent stage of photosynthesis, what is the immediate source of the electrons that replace those lost from photosystem II?

  A. Reduced NADPB. ATP hydrolysisC. The photolysis of waterD. Carbon dioxide

  (Total for Question SECTION-A4 is 1 mark)
• 5

  Question SECTION-A5 (1 mark)

  A sample of DNA is found to contain 22 percent adenine. What percentage of the bases in this sample is guanine?

  A. 22 percentB. 28 percentC. 44 percentD. 56 percent

  (Total for Question SECTION-A5 is 1 mark)
• 6

  Question SECTION-A6 (1 mark)

  Which process directly generates the majority of ATP produced during aerobic respiration of one glucose molecule?

  A. Glycolysis in the cytoplasmB. The link reactionC. Oxidative phosphorylation at the inner mitochondrial membraneD. Substrate-level phosphorylation in the Krebs cycle

  (Total for Question SECTION-A6 is 1 mark)
• 7

  Question SECTION-A7 (1 mark)

  In a mammalian cardiac cycle, the atrioventricular valves close as a direct result of which event?

  A. Ventricular pressure exceeding atrial pressureB. Atrial pressure exceeding ventricular pressureC. Ventricular pressure exceeding aortic pressureD. The opening of the semilunar valves

  (Total for Question SECTION-A7 is 1 mark)
• 8

  Question SECTION-A8 (1 mark)

  Which term describes a mutation in which a single base pair is inserted into a gene, altering every codon downstream?

  A. Silent substitutionB. Frameshift mutationC. Chromosome non-disjunctionD. Polyploidy

  (Total for Question SECTION-A8 is 1 mark)
• 9

  Question SECTION-A9 (1 mark)

  Water moves from a plant's root cortex into the xylem. Which term best describes movement of water through the continuous system of cell walls?

  A. The symplast pathwayB. The apoplast pathwayC. The vacuolar pathway onlyD. Active transport through channel proteins

  (Total for Question SECTION-A9 is 1 mark)
• 10

  Question SECTION-A10 (1 mark)

  Which of the following is the best description of a species according to the biological species concept?

  A. A group of organisms that look identicalB. A group of organisms occupying the same habitatC. A group of organisms that can interbreed to produce fertile offspringD. Any group given the same genus name

  (Total for Question SECTION-A10 is 1 mark)
• 11

  Question SECTION-A11 (1 mark)

  During a spirometer investigation a student measures a resting tidal volume of 0.5 dm^3 and a breathing rate of 15 breaths per minute. What is the pulmonary ventilation rate?

  A. 7.5 dm^3 per minuteB. 30 dm^3 per minuteC. 0.033 dm^3 per minuteD. 15 dm^3 per minute

  (Total for Question SECTION-A11 is 1 mark)
• 12

  Question SECTION-A12 (1 mark)

  Which type of immunity is provided when a person is given an injection of ready-made antibodies from another source?

  A. Active natural immunityB. Active artificial immunityC. Passive artificial immunityD. Passive natural immunity

  (Total for Question SECTION-A12 is 1 mark)
• 13

  Question SECTION-A13 (1 mark)

  In a dihybrid cross between two organisms heterozygous at both unlinked loci (AaBb x AaBb), what is the expected phenotypic ratio in the offspring?

  A. 3 : 1B. 1 : 2 : 1C. 9 : 3 : 3 : 1D. 1 : 1 : 1 : 1

  (Total for Question SECTION-A13 is 1 mark)
• 14

  Question SECTION-A14 (1 mark)

  A resting neurone maintains a potential difference across its membrane. Which mechanism is chiefly responsible for establishing this resting potential?

  A. Voltage-gated sodium channels openingB. The sodium-potassium pump and differential membrane permeability to potassiumC. The refractory periodD. Saltatory conduction along myelinated axons

  (Total for Question SECTION-A14 is 1 mark)
• 15

  Question SECTION-A15 (1 mark)

  Which statement about the role of stem cells in specialised tissue is correct?

  A. Stem cells have permanently lost the ability to divideB. Stem cells are undifferentiated and can give rise to specialised cell typesC. All stem cells are totipotent throughout lifeD. Stem cells contain a different genome from the body's other cells

  (Total for Question SECTION-A15 is 1 mark)

Section B

Structured and extended response questions. Answer ALL the questions.

• 1

  Question SECTION-B1 (12 marks)

  Enzymes are biological catalysts essential to metabolism. (a) Describe the induced-fit model of enzyme action and explain how it accounts for enzyme-substrate specificity. (4 marks) (b) A student investigated the activity of the enzyme catalase from potato by measuring the volume of oxygen released from hydrogen peroxide over a range of temperatures from 10 to 60 degrees C. Explain the shape of the curve you would expect, referring to kinetic energy and denaturation. (4 marks) (c) Explain how a non-competitive inhibitor reduces the rate of an enzyme-controlled reaction and why increasing substrate concentration does not restore the maximum rate. (4 marks)

  (Total for Question SECTION-B1 is 12 marks)
• 2

  Question SECTION-B2 (10 marks)

  The mammalian heart and circulatory system transport substances around the body. (a) Describe the sequence of electrical events that coordinates one heartbeat, starting at the sinoatrial node and ending with ventricular contraction. (5 marks) (b) Explain why a delay occurs at the atrioventricular node and why this delay is important. (2 marks) (c) Explain how the structure of an artery is adapted to its function, giving THREE structural features and the function of each. (3 marks)

  (Total for Question SECTION-B2 is 10 marks)
• 3

  Question SECTION-B3 (9 marks)

  Photosynthesis and respiration are interlinked metabolic pathways in plant cells. (a) State precisely where the light-dependent reactions and the Calvin cycle each occur within a chloroplast. (2 marks) (b) Explain the roles of reduced NADP and ATP produced in the light-dependent stage in the Calvin cycle. (3 marks) (c) A plant is moved from bright light into darkness. Predict and explain what will happen to the concentrations of ribulose bisphosphate (RuBP) and glycerate 3-phosphate (GP) in the stroma. (4 marks)

  (Total for Question SECTION-B3 is 9 marks)
• 4

  Question SECTION-B4 (8 marks)

  The human immune system defends the body against pathogens. (a) Describe the sequence of events in the humoral immune response following infection by a novel bacterial pathogen, from antigen presentation to antibody production. (6 marks) (b) Explain why a second exposure to the same pathogen produces a faster and larger antibody response than the first. (2 marks)

  (Total for Question SECTION-B4 is 8 marks)
• 5

  Question SECTION-B5 (8 marks)

  Genes control the production of proteins. (a) Describe the process of transcription in a eukaryotic cell. (4 marks) (b) Explain how the base sequence of the messenger RNA determines the primary structure of a protein during translation. (4 marks)

  (Total for Question SECTION-B5 is 8 marks)
• 6

  Question SECTION-B6 (8 marks)

  Ecosystems can be studied quantitatively. (a) Define the terms biomass and gross primary productivity (GPP). (2 marks) (b) Explain why only a small percentage of energy is transferred from one trophic level to the next. (3 marks) (c) A student sampled two grassland sites to compare species diversity using a diversity index. Describe how the student should collect valid data using quadrats, and state one reason why random sampling is important. (3 marks)

  (Total for Question SECTION-B6 is 8 marks)
• 7

  Question SECTION-B7 (7 marks)

  Homeostasis maintains a stable internal environment. (a) Explain the principle of negative feedback in the control of blood glucose concentration, naming the hormones involved. (4 marks) (b) Describe how insulin causes a fall in blood glucose concentration once it has bound to its target cells. (3 marks)

  (Total for Question SECTION-B7 is 7 marks)
• 8

  Question SECTION-B8 (7 marks)

  Biodiversity can be assessed at genetic, species and habitat levels. (a) Explain what is meant by genetic diversity and describe TWO ways it can be increased within a population. (3 marks) (b) Explain how natural selection can lead to a change in allele frequency in a population over several generations, using an example such as antibiotic resistance in bacteria. (4 marks)

  (Total for Question SECTION-B8 is 7 marks)
• 9

  Question SECTION-B9 (6 marks)

  Cell division is fundamental to growth and reproduction. (a) Describe what happens to the chromosomes during prophase and metaphase of mitosis. (3 marks) (b) Explain two ways in which meiosis produces genetic variation among gametes. (3 marks)

  (Total for Question SECTION-B9 is 6 marks)
• 10

  Question SECTION-B10 (6 marks)

  Water potential affects the movement of water into and out of cells. (a) Define water potential and state the units in which it is measured. (2 marks) (b) A plant cell with a water potential of -800 kPa is placed in a solution with a water potential of -300 kPa. Predict the direction of net water movement and explain what will happen to the cell. (4 marks)

  (Total for Question SECTION-B10 is 6 marks)
• 11

  Question SECTION-B11 (4 marks)

  State the meaning of the term 'monoclonal antibody' and give ONE named medical use, explaining briefly how the antibody's specificity makes it suitable for that use. (4 marks)

  (Total for Question SECTION-B11 is 4 marks)