AQA A-Level Biology Paper 1 exam 2023, Exams of Nursing

Download AQA A-Level Biology Paper 1 exam 2023 and more Exams Nursing in PDF only on Docsity! AQA A-Level Biology Paper 1 exam 2023 Describe the role of a ribosome in the production of a polypeptide. /3 - correct answer 1. mRNA binds to ribosome; 2. Idea of TWO codons/binding sites; 3. tRNA with ANTICODONS binds; 4. (Catalyses) formation of PEPTIDE bond between AMINO ACIDS (held by tRNA molecules); 5. Moves along (mRNA to the next codon); Describe the structure of glycogen. /2 - correct answer 1. Polysaccharide of α-glucose; OR polymer of α-glucose; 2. (Joined by) glycosidic bonds OR Branched structure; NHE3 actively transports one sodium ion into the cell in exchange for one proton (hydrogen ion) out of the cell. Use your knowledge of transport across cell membranes to suggest how NHE3 does this. /3 - correct answer 1. Co-transport; 2. Uses (hydrolysis of) ATP; 3. Sodium ion and proton bind to the protein; 4. Protein changes shape (to move sodium ion and/or proton across the membrane); Explain the curves for max protease activity over time at 50C and 60C. /4 - correct answer 1. Both denatured (by high temperature); 2. Denaturation faster at 60 °C due to more (kinetic) energy; 3. Breaks hydrogen/ionic bonds (between amino acids/R groups); 4. Change in shape of the active site/active site no longer complementary so fewer enzyme-substrate complexes formed; AQA A-Level Biology Paper 1 exam 2023 Describe the action of these membrane-bound dipeptidases and explain their importance. /2 - correct answer 1. Hydrolyse (peptide bonds) to release amino acids; 2. Amino acids can cross (cell) membrane; OR Dipeptides cannot cross (cell) membrane; OR Maintain concentration gradient of amino acids for absorption; Explain why the scientists suggested that patients should be treated with both the current antibiotic and the new one. Use information from Figure 2 (old antibiotic decreases number of bacteria, new one decreases it more) and your knowledge of evolution of antibiotic resistance in bacteria in your answer. /3 - correct answer 1. (From Fig 2) New/old antibiotic does not kill all bacteria; OR (From Fig 2) Some bacteria are resistant to the new/old antibiotic; 2. Resistant bacteria will reproduce to produce (more) resistant bacteria; 3. (Use of both) one antibiotic will kill bacteria resistant to the other antibiotic; OR Unlikely that bacteria are resistant to both the new and the old antibiotic; OR Use of both antibiotics (likely to) kill all/most bacteria; When measuring the leakiness of herbicide-treated cell membranes to ions, why did the scientists gently shake the flasks containing the leaf discs? /1 - correct answer (Shaking) So all surfaces of the leaf discs are exposed (to water)/so all submerged; OR To maintain diffusion/concentration gradient (for ions out of leaf discs); AQA A-Level Biology Paper 1 exam 2023 Suggest an explanation for the appearance of the cell-surface membrane as two dark lines. [3 marks] - correct answer 1.Membrane has phospholipid bilayer; 2.Stain binds to phosphate/glycerol; 3.On inside and outside of membrane; Describe how substances move across cell-surface membranes by facilitated diffusion. [3 marks] - correct answer 1. Carrier/channel protein; 2.(Protein) specific/complementary to substance; 3.Substance moves down concentration gradient; Give an advantage of asexual and sexual reproduction. /2 - correct answer Asexual has fewer stages so quicker OR Only one parent involved so can colonise new environment OR Produces clone so successful (geno/pheno)type maintained; Sexual increases genetic diversity so greater chance of survival/success; Explain why the maximum initial reaction rate (reached at high substrate concentrations) is higher with competitive inhibitors than with non-competitive. /4 - correct answer 1. CI binds to active sites of enzyme but NCI away from active site; 2. (Binding of) CI does not cause change in shape of active site but NCI does; 3. So with CI, at high substrate concentrations (active) enzyme still available but with NCI (active) enzymes no longer available; 4. At higher substrate concs likelihood of enzyme-substrate collisions increases with CI but this is not possible with NCI; Give two reasons why grassy strips with a variety of plant species increase the biodiversity of animals. [2 marks] - correct answer 1. Increase in plant diversity leads to more TYPES of food for animals; 2.Increase in variety of animals leads to increase in predator species; AQA A-Level Biology Paper 1 exam 2023 3.Increase in niche/habitat; The scientists decided to collect animals, sorting the soil samples by hand, for 40 minutes. Suggest how the scientists decided that 40 minutes was an appropriate time. [2 marks] - correct answer 1. Repeat soil sorting for different times and record number of species collected; 2. Find optimum time / time beyond which further sorting does not lead to increase in animal species found; Do you agree that these results are significant? /1 (priniciple of 2 × SD) - correct answer 1. Overlap of 2 × SD shows probability of differences (in means) being due to chance is greater than 0.95; What was the range in the number of copies of the AMY1 gene? /1 - correct answer 2 to 11 Explain why the standard deviation for the mean (4.4) is ±2.0. /1 - correct answer Data show great variation (around mean) OR 4.4 ± 2 × SD includes most of the values measured; The scientists calculated a correlation coefficient, R, from their data. They found R = 0.50, with P <0.0001. Explain the meaning of the result of their calculations. [3 marks] - correct answer 1. Shows a positive correlation; 2. There probability of getting this correlation by chance is less than 0.0001; 3. Correlation is highly significant; AQA A-Level Biology Paper 1 exam 2023 The number of copies of the AMY1 gene, coding for salivary amylase, is unlikely to affect people's ability to digest starch. Explain why. [3 marks] - correct answer 1. Little digestion of starch by salivary amylase OR starch in mouth for a short period OR salivary amylase inactivated by stomach acid; 2. Amylase also secreted by pancreas; 3. So (most) starch digestion occurs in small intestine; Explain how the organic bases help to stabilise the structure of DNA. [2 marks] - correct answer 1. Hydrogen bonds between the base pairs holds two strands together; 2. Many hydrogen bonds provides strength; Suggest one advantage of showing the genetic code as base sequences on mRNA, rather than triplets on DNA. [1 mark] - correct answer ribosomes assemble polypeptides using mRNA code OR DNA has two strands each with a different (complementary) base sequence; Suggest the role of the mRNA stop codons. /2 - correct answer 1. Stop translation; 2. Result in detachment of polypeptide chain from ribosome; Give the formula for calculating the percentage saturation of haemoglobin with oxygen. [1 mark] - correct answer oxygenated haemoglobin ÷ maximum saturation × 100 The first molecule of oxygen to bind causes a change in the shape of the haemoglobin molecule. This change of shape makes it easier for other oxygen molecules to bind to the haemoglobin molecule. Explain how the haemoglobin saturation graph provides evidence for this. AQA A-Level Biology Paper 1 exam 2023 A student concluded from a graph of the data in Table 5 that the bacterium lives at 15 °C, which is the optimum temperature for enzyme activity. Do the data support the student's conclusion? [4 marks] - correct answer Yes: 1. Expect optimum temperature of enzyme to be same/similar to temperature where bacterium lives; 2. Optimum temperature for enzyme (appears to be around) 15 °C; No: 3. Need data from more temperatures (between 10 °C and 20 °C); 4. Data for only isolated enzyme OR Isolation may affect activity; Each phloem-sap-feeding insect receives a few gut bacteria from its parent. Suggest how this has caused a reduction in genetic diversity of the bacteria. [2 marks] - correct answer 1. (Only few bacteria passed from parent, so) only a few (copies of) genes passed on (in bacteria); 2. May not/does not include all alleles (of genes, so diversity reduced) OR Small number of bacteria transmitted means unrepresentative sample; A scientist found that leaf-chewers and xylem-sap-feeders had a greater effect on plant growth than phloem-sap-feeders (greater reduction in leaf area). AQA A-Level Biology Paper 1 exam 2023 Other than environmental factors, give two features the scientist would have controlled in his experiment to ensure this conclusion was valid. [2 marks] - correct answer 1. Number/mass/density of insects per plant; 2. Stage of development/size of plants/insects;