OCR 2023 Biology A H420/01: Biological processes A Level Question Paper & Mark Scheme (Merged)

2 OCR 2023 Section A You should spend a maximum of 20 minutes on this section. Write your answer to each question in the box provided. 1 Which description of biological molecules is correct? A DNA and RNA are both polymers of nucleotides. B Hydrolysis of sucrose produces fructose and β-glucose. C Proteins are polymers of amino acids and are broken down in condensation reactions. D Starch is a polymer of the monosaccharide maltose. Your answer [1] 2 Which statement about lipids is correct? A Phospholipids are formed by esterification of glycerol with three molecules of fatty acid. B Phospholipids containing unsaturated fatty acids can increase the fluidity of cell membranes. C Triglycerides are good energy stores although they release less energy than an equal mass of polysaccharide. D Triglycerides form the bilayer of the plasma membrane. Your answer [1] 3 Turn over 3 Which statement about the structure of amino acids is not true? A Amino acids contain amino and carboxyl groups. B Amino acids contain the elements hydrogen, carbon and oxygen only. C Each amino acid has a unique R group. D The R groups in amino acids can be polar or non-polar. Your answer [1] 4 Which of the options is a feature of collagen? A It allows alveoli to recoil B It dissolves in water C It is flexible D It is the main protein found in hair Your answer [1] 5 Increasing the pH of an enzyme solution from 7.4 to 8.0 causes the rate of the reaction to fall by 90%. When the pH of the solution returns to 7.4 the rate of reaction returns to its original value. Which of the statements about this enzyme-controlled reaction explains these observations? A Increasing the pH from 7.4 to 8.0 breaks hydrogen bonds but returning the pH to 7.4 allows them to re-form. B Increasing the pH from 7.4 to 8.0 changes the shape of the active site and so the substrate binds more tightly. C Increasing the pH from 7.4 to 8.0 denatures the enzyme. D Reducing the pH below 7.4 will reduce the rate of re