AQA A-Level Biology Paper 1 Study Guide: Exam Questions and Answers (2024-2025), Exams of Biology

Download AQA A-Level Biology Paper 1 Study Guide: Exam Questions and Answers (2024-2025) and more Exams Biology in PDF only on Docsity! AQA A-Level Biology Paper 1 AQA A-Level Biology Paper 1 Study Guide Exam Questions and Answers (41 Terms) 2024-2025 Describe the role of a ribosome in the production of a polypeptide. /3 - Answer: 1. mRNA binds to ribosome; 2. Idea of TWO codons/binding sites; 3. tRNA with ANTICODONS binds; 1 AQA A-Level Biology Paper 1 4. (Catalysis) 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 - 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 - 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 - 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); 2 AQA A-Level Biology Paper 1 5. Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface; OR Fluid in the end of the tracheoles that moves out (into tissues) during exercise so larger surface area (for gas exchange); 6. Body can be moved (by muscles) to move air so maintains diffusion/concentration gradient for oxygen/carbon dioxide; The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain oxygen from water. Some other species of insect have larvae that are a similar size and shape to damselfly larvae and also live in water. These larvae do not actively hunt prey and do not have gills. Explain how the presence of gills adapts the damselfly to its way of life. /2 - Answer: 1. Damselfly larvae has high(er) metabolic/respiratory (rate); 2. (So) uses more oxygen (per unit time/per unit mass); (ignore uptakes more oxygen) 5 AQA A-Level Biology Paper 1 How do you calculate % uncertainty in area? - Answer: % uncertainty in length + % uncertainty in width Suggest how the student could improve the quality of her scientific drawing. /2 - Answer: 1. Don't use shading; 2. Only use single lines/don't use sketching (lines)/ensure lines are continuous/connected; 3. Add further labels/annotations; 4. Don't cross label lines; 5. Add magnification/scale (bar); How large should a sample be? - Answer: Large enough to be representative of the population What type of molecule is (hexadecenoic acid)? /2 - Answer: saturated fatty acid No organelles are visible in the cytoplasm of this red blood cell. Suggest why. [1 mark] - Answer: Cytoplasm of red blood cell filled with hemoglobin; Before the cell was examined using the electron microscope, it was stained. This stain caused parts of the structure of the cell-surface membrane to appear as two dark lines. 6 AQA A-Level Biology Paper 1 Suggest an explanation for the appearance of the cell-surface membrane as two dark lines. [3 marks] - 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] - 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 - 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 - 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; 7 AQA A-Level Biology Paper 1 3. So (most) starch digestion occurs in small intestine; Explain how the organic bases help to stabilise the structure of DNA. [2 marks] - 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] - 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 - 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] - Answer: oxygenated haemoglobin ÷ maximum saturation × 100 The first molecule of oxygen to bind causes a change in the shape of the haemoglobin molecule. 10 AQA A-Level Biology Paper 1 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. [2 marks] - Answer: 1. At low partial pressure of oxygen, little increase in saturation as oxygen increases; 2. (then) rapid rise as it gets easier for oxygen to bind; Suggest how the scientists could adapt their method to determine which tissue carried the radioactively labelled sucrose. [2 marks] - Answer: 1. Take thin (horizontal) sections of plant tissue/stem; 2. Place against photographic film in dark for several hours / carry out autoradiography; The scientists dried the plant samples in an oven at 100 °C. Give two reasons why they used this temperature. [2 marks] - Answer: 1. Evaporates all water 2. (But) does not burn (organic compounds); 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. [4 marks] - Answer: 1. Mutation; 2. Results in Nm cell with allele for resistance to 11 AQA A-Level Biology Paper 1 one antibiotic/to named antibiotic; 3. (This) cell survives and passes the allele for resistance to offspring; 4. Process repeated with different genes conferring resistance to each of the other (two) antibiotics; Explain two ways in which the structure of fish gills is adapted for efficient gas exchange. [2 marks] - Answer: 1. Many lamellae/filaments so large surface area; 2. Thin (surface) so short diffusion pathway; Cells lining the ileum of mammals absorb the monosaccharide glucose by co- transport with sodium ions. Explain how. [3 marks] - Answer: 1. Sodium ions actively transported from ileum cell to blood; 2. Maintains/forms diffusion gradient for sodium to enter cells from gut (and with it, glucose); 3. Glucose enters by facilitated diffusion with sodium ions; A student puts amylase and starch inside of Visking tubing in a beaker of water. She then tests the solution in the beaker with Biuret's, Benedict's and potassium iodide. Explain the results. /3 - Answer: 1. Biuret: protein molecules too large to pass through tubing; (not enzyme) 2. Iodine in potassium iodide solution: starch 12